Lupine Publishers | Addiction to Tobacco: A War That Begins to Win

 Lupine Publishers | Journal of Psychology and Behavioral Sciences

Opinion

For several centuries’ humanity has become addicted to tobacco, as a social entrance to an allowed addiction, and that each smoker was charged its respective bill, with ways to die of the most brutal and suffered possible. The complications of nicotine addiction are based on the form of its entry route, which is respiratory due to smoking, and hence the complications of the referred habit, mainly emphysema and lung cancer. The national survey of addictions reveals that in Mexico 18.5% of the population smokes; that is, almost 20 million people with tobacco habit; almost 50 thousand cases of deaths per year have been reported and that makes us an average of 130 to 140 deaths per day, following the worldwide trend of starring in the number of deaths. How is the death of a chronic smoker patient? It may be due to lung cancer, emphysema or chronic bronchitis, as well as severe sleep apnea, all of which are sponsored by chronic asphyxia, with loss of lung exchange capacity that neither the highest contribution of home or hospital oxygen can compensate; in a few words in the final stage, they agonize, with nothing to do except connect them to an artificial respirator and wait for their slow death; In our country, despite the fact that the number of tobacco addicts has stopped, we will continue to pay the costs of chronic treatment to long-term smokers, say at least 20 more years, as long as the measures adopted take effect.

That without counting other problems such as increased cancer in other parts of the body such as the lip, larynx, urinary bladder, breast, liver, colon, rectum, etc. (ufff, tremendous). Do you want to know more that has been done to decrease your addiction? In our country, legends have been placed in the packs and their tax has been increased and therefore its cost; spaces allowed for smoking have been limited (in enclosed spaces) and advertising and cartels have been placed on a mandatory basis in various public buildings, especially hospitals. The problem is that the fact remains that it is not a generalized prohibition on any enclosed space, and children are still potential victims, and that the tax increase is not as desirable as it could be, but something is something. And it is the only addiction against which there is a real battle, and from which results are expected but in the medium or long term, we will not immediately have the desired answers. Hopefully with alcohol you have the same combat strategies, so that they begin to reduce the cases and complications that are a serious blow to public health.

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Lupine Publishers| Understanding the Demographic and Clinical Characteristics of Heart Failure to Improve Management Practices: The Caribbean Perspective

 Lupine Publishers| Journal of Cardiology Research & Reports

Abstract

Heart Failure is a worldwide burden. The prevalence, incidence, mortality and morbidity rates reported show geographic variations, depending on the different aetiologies and clinical characteristics observed among patients with this complex syndrome. In this review we focus on the Afro Caribbean population with Heart Failure providing data review about the Heart Failure etiology based in previous Clinical Trials In addition we provide suggestions based in these Trials and our recent observational clinical studies that might be useful to improve our current Heart Failure Guideline-Directed Medical Therapy . Finally we highlight the need for more regional research.

Keywords: Caribbean region, Heart failure, Etiology, Management

Abbrevations: CHF: Congestive Heart failure; HF: Heart Failure; MI: Myocardial Infarction; SHF: Systolic Heart Failure; HT: Hypertension; DM: Diabetes Mellitus; HFNEF: Heart Failure with a Normal Ejection Fraction; DCM: Dilated Cardiomyopathy; NIDCM: Non-Ischemic Dilated Cardiomyopathy; IDCM: Ischemic Dilated Cardiomyopathy; LVSD: Left Ventricle Systolic Dysfunction; HFmrEF: Heart Failure with mid-range Ejection Fraction; HFrEF: Failure with Reduced Ejection Fraction; ARNI: Angiotens in Receptor Neprilysin Inhibitor

Introduction

There is no doubt that Heart Failure is a complex syndrome that results from any structural or functional impairment of ventricular filling or ejection of blood [1], moreover, Heart Failure is a disease in which there are striking population differences in almost every aspect of the disease. It has been recognized that the cause of Heart Failure is predominantly ischemic disease in nonblack but is related primarily to Hypertension in Blacks [2], accordingly, this statements should be confirmed in Afro-Caribbean patients because population differences exist that may be attributable to differences in social factors, genetics, environment , lifestyle, comorbidities, and complex interactions among this factors [3].

Heart failure research data in African American: can also them be applied in afro Caribbean patients?

The majority of the data on Heart Failure in African descendant has been done in African American population and that research should be validated in the Caribbean Region. The U.S. Office of Management and Budget [4] defines “Black” of “African American” as having origins in any of the Black racial groups of Africa. The term African Caribbean/Afro-Caribbean when used in Europe usually refers to people with African ancestral origins who migrated via the Caribbean islands [5]. The majority of Jamaicans (92.1%) identify as black [6] however there are other ethnic groups [7]: Mixed (6.1%), Asian (0.8%), others (0.4%). Much of Jamaica’s black population is of African or partially African descent with many being able to trace their origins to West Africa and the term African Caribbean must be restricted to an African descent person originating from the Caribbean. Although it seems reasonable to think in terms of African Descendant Data the Heart Failure clinical studies in African American should be validated in the Caribbean Region.

Disparities Between White and Black: Studies In African American Population

Recent research continues suggesting disparities between white and black populations: In a Random Cohort of 2,188 participants from The Reasons for Geographic and Racial Differences in Stroke Project - REGARDS-[8] without prevalent cardiovascular disease studied by race was showed that Plasma N-terminal pro b-type natriuretic peptide (NTproBNP ) levels are significantly lower in blacks as compared to whites however the contribution of endogenous suppression of Natriuretic Peptide system on cardiovascular disease in blacks remains to be established On the other hand , in relation with the etiology of patients with Heart Failure, when defined as a prior documented myocardial infarction or known epicardial coronary artery disease, ischemic heart disease appears to be present in just 35% of African- American patients and the exact mix of hypertensive heart disease and idiopathic dilated cardiomyopathy (as well as the influence of alcoholic cardiomyopathy) is not discernible from published data. Therefore, the contribution of hypertensive heart disease as the sole explanation of Left Ventricle dysfunction is likely to be between the 30% range reported in the SOLVD registry or the>50% incidence suspected in recently reported β-blocker trials [9] (Figure 1). Moreover in the Multi-Ethnic Study of Atherosclerosis --MESA-[10] , a cohort study of 6814 participants of 4 ethnicities (African American :27.8%) , African Americans had the highest incidence rate of Congestive Heart failure (CHF) and showed that the mechanisms of CHF also differed by ethnicity namely an interim myocardial infarction had the least influence among African Americans (Figure 2).

Figure 1: Heart Failure in African Americans: Incidence of Coronary Artery Disease. Pooled Data from major Trials in Heart Failure reporting probable cause of Left Ventricle Systolic Dysfunction. US Carv= =US Carvelidol Heart failure Trials Program; BEST=Beta Blocker Evaluation of Survival Trial; AA=African American; Non-AA=Non African American [9].

Figure 2: Nelson-Aalen Plots of Cumulative Hazards for Congestive Heart Failure (CHF) among Multi-Ethnic Study of Atherosclerosis Study participants without an interim Myocardial Infarction [10].

That is , as the Time course and pattern of development of heart failure (HF) can be primarily caused by myocardial infarction (MI), with pronounced remodeling and shape change leading to systolic heart failure (SHF) or HF primarily caused by hypertension (HT), with or without diabetes mellitus (DM), leading to heart failure with a normal ejection fraction (HFNEF) however both, patients with a history of MI and patients with HT may experience periods of HFNEF and finally Systolic heart failure (SHF) with a reduced ejection fraction: HFrEF [11] .More evidence about the Primary Cause of Heart Failure in African American can be also analyzed from the Baseline Characteristics of the African-American Heart Failure Trial [12] in which about 1000 patients showed a history of Ischemic Heart Disease in just 23% and also in the recent Prospective Comparison of ARNI with ACEI to Determine Impact on Global Mortality and Morbidity in Heart Failure (PARADIGMHF) Sub study [13] in which the Black participants (N=428) showed a history of Myocardial Infarction in just 17.3 % vs 48.3 % in the White participants (N=5544) , strengthening the Heart Failure mechanism with less influence of an interim of a myocardial infarction. From the few studies among Afro Caribbean population with Heart Failure is worth mentioning the study of Afro-Caribbean heart Failure in the United Kingdom [14]: compared with the white population, Heart Failure in Afro Caribbean Patients (n=211) was mostly associated with Non Ischemic Cardiomyopathy (87vs 59%), Dilated Cardiomyopathy (27.5 vs 10.8%) and Hypertensive Cardiomyopathy (12.3 vs 2.2%) and even more interesting is the fact that Cardiac Amyloidosis was confirmed in 11.4 vs 1.6% .

Heart failure in african-americans

As suggested for previous Clinical Trials Experience, Heart Failure Etiology [15] in African-Americans-AA:

a) Is much more associated with Non Ischemic etiology of Left Ventricular Dysfunction (LVD).

b) Hypertension is considered the putative disease process but dilated cardiomyopathies and Diabetes-related diseases are common.

c) Coronary Artery Disease remains a cause of LVD but is less common in AA than in whites.

Why African Americans, and extensively Afro-Caribbean, have more Heart Failure?

It has been proposed [16] the following mechanisms:

a) The impact of Modifiable Risk Factors.

b) Neuro hormonal imbalances and endothelial dysfunction.

c) Genetic Polymorphisms and

d) Socioeconomic Factors and Quality of Care.

It is clear that Hypertension remains as the most important risk factor: A Prevalence estimates for traditional CVD risk factors in Jamaicans showed [17]: hypertension, 25%; diabetes, 8%; hypercholesterolemia, 12%; obesity, 25%; smoking 15%. In addition, 35% of Jamaicans had pre hypertension, 3% had impaired fasting glucose and 27% were overweight. A higher proportion of women had diabetes, obesity and hypercholesterolemia while the prevalence of pre hypertension and cigarette smoking was higher in men. In the other hand, some race-specific differences in endothelial function and predisposition of AA to vascular diseases are [18]: (a) increased oxidative stress (b) decreased Nitrite Oxide availability (c) Exaggerated vasoconstrictor response and (d) attenuated responsiveness to Vasodilators and Nitric Oxide. In addition, Genetic Polymorphisms associated with the risk of Heart failure in AA has been considered [16] : (a) Beta 1 Adrenergic Receptor (b) Alpha 2c Adrenergic Receptor (c ) Aldosterone Synthase (d) G Protein (e) Transforming G Grow Factor Beta (f) Nitric Oxide Synthase (g) Transthyretin. This has been recently evaluated for Dungu [14]: In a comparison with white patients, the author found ATTR V122l and Cardiac Amyloidosis all types in 8.5 % vs 0.3 % and 11.4% vs 1.6 % respectively of Afro-Caribbean vs. White patients with Heart Failure living in the United Kingdom.

Clinical studies in afro-caribbean patients with heart failure living in jamaica

The available data of Afro Caribbean Heart Failure, including studies in Jamaica, is scarce. Tulloch Reid [19] brought the attention to cases with unexplained Dilated Cardiomyopathy and reported the association of HTLV-1 seropositivity and Unexplained Dilated Cardiomyopathy (DCM) in Jamaican patients. This author also reported the experience of 26 cases (45±11 years-old) with unexplained dilated cardiomyopathy at Kingston Public Hospital (personal communication). Lalljie [20] reported the experience in 100 Jamaican with heart failure patients: 49% had echocardiograms, of these 39% had ejection fractions (EF)>40%, 34 % had EF 21-40 % and 27% had EF<20%. Hypertensive heart disease was found in 54%, hypertensive cardiomyopathy in 14 % and ischemic heart disease just in 26 %. Accordingly and knowing that the majority of the data on Heart Failure in African descendant has been done in African American population and that these studies had to be validated in the Caribbean Region we planned some observational studies [21-23] in order to know:

a) The cardiovascular risk profile of patients with, angiographycally proven, Non-Ischemic Dilated Cardiomyopathy (NIDCM) vs Ischemic Dilated Cardiomyopathy (IDCM) (Figure 3).

Figure 3 : The presence or the absence of the most important traditional cardiovascular factors (Hypertension=HTN and Diabetes-DM), which have been described as strongly correlated with coronary artery disease, are not necessarily predictive of angiographycally-proven Non-Ischemic Dilated Cardiomyopathy (NIDCM) in an Afro Caribbean population with HFrEF [21].

b) The demographic and clinical features of patients with left ventricle systolic dysfunction (LVSD) and differences between Heart Failure with mid-range Ejection Fraction (HFmrEF) and Heart Failure with Reduced Ejection Fraction (HFrEF) (Figure 4).

Figure 4 : The presence or the absence of the most important traditional cardiovascular factors (Hypertension=HTN and Diabetes-DM), which have been described as strongly correlated with coronary artery disease, are not necessarily predictive of angiographycally-proven Non-Ischemic Dilated Cardiomyopathy (NIDCM) in an Afro Caribbean population with HFrEF [21].

c) The proportion and clinical features of patients with angiographycally proven Ischemic vs Non Ischemic Heart Failure with Reduced Ejection Fraction (HFrEF) from our Coronary Angiographies database (Figure 5).

Figure 5 : From a total of 380 patient’s angiographycally evaluated during the study period, 67 patients were included in the analysis. The prevalence (%) of patients with NIDCM was 55%. With the exception of age (59 vs 65, p<0.03) and confirmed myocardial infarction-MI (2 vs 25%, p<0.04) there were no significant differences (p<0.05) in the prevalence of CAD risk factors suggesting that among Afro-Caribbean patients with HFrEF, despite that both groups of patients were exposed to similar CAD risk factors, angiographycally proven NIDCM is more frequent that IDCM. This underlines the hypothesis that other factors may play an important role in the etiology of the Afro Caribbean Heart Failure [23].

Lessons From the Clinical Studies on Afro Caribbean Patients with Heart Failure Living in Jamaica

From a broad perspective, these studies are suggesting that:

a) Although both groups (NIDCM vs IDCM) has been exposed over their lifetime to the same strong risk factors for CAD, they potentially and can develop the same outcome (DCM) but one group with angiographycally normal epicardial coronary arteries and the other with angiographycally abnormal coronary arteries.

b) Hypertension and Diabetes are the most important risk factors associated with Dilated Cardiomyopathy in this Afro Caribbean population.

c) Afro-Caribbean patients with heart failure and are mainly hypertensive with or without diabetes and grossly half of them develop LVSD due to non-ischemic causes.

d) They demonstrate a distinct etiological but similar clinical profile when they are classified in the category of HFmrEF and HFrEF

e) Among Afro-Caribbean patients with HFrEF, angiography ally proven NIDCM is more frequent (55vs.45%) that IDCM suggesting that despite both groups of patient’s exposure to the similar CAD risk factors, other factors play an important role in etiology of the left ventricle failure.

Understanding Afro Caribbean Heart Failure to Improve the Management Practices

According with the 2013 ACC/HFA Guidelines [1] the magnitude of benefit for Reduction in Mortality and Reduction in HF Hospitalizations demonstrated in RCTs is ,respectively, as follows: a) ACE Inhibitor or ARB: 17% and 31% b) Beta Blockers: 34% and 41% c) Aldosterone Antagonist: 30% and 35% and d) Hydralazine/ Nitrate (HYD/ISDN): 43% and 33%, accordingly the Pharmacologic treatment recommendation for persistently symptomatic African American patients with Stage C HFrEF, class III-IV, in order to reduce morbidity and mortality, and in addition to ACE Inhibitor, or ARB and in conjunction with Beta Blocker is Hydralazine/Nitrates (Class I, LOE A). Moreover, the 2017 ACC/AHA Guidelines Update [24] has recommended for patients with chronic HFrEF, to reduce morbidity and mortality the Angiotens in Receptor Neprilysin Inhibitor (ARNI) in conjunction with Beta Blocker (Class I, LOE B-R) and for patients with chronic symptomatic HFrEF, NYHA class II-III, who tolerate an ACE Inhibitor or ARB: the ARNI, to replace an ACE Inhibitor or ARB (Class I, LOE B-R) More understanding about the population of African Americans has been mentioned in the 2017 ACC Expert Consensus Decision Pathway for Optimization of Heart Failure with Reduced Ejection Fraction [25] which has stated that in African Americans Sacubitril/Valsartan and Ivabradine were tested in populations with few African Americans receiving HYD/ ISDN. Thus, for this population, there are no data for the efficacy or safety of ARNI in patients with an indication for HYD/ISDN.

Moreover, both HYD/ISDN and ARNI purportedly act via upregulation of cGMP pathways, which may increase the risk of hypotension. Additionally, the risk of angioedema with ACEI and ARNI is particularly high in African-American patients (0.5% with ACEI and 2.4% with ARNI); this risk, however, should not preclude initiation of these agents absent a documented history of angioedema. Two options would exist: A. Establish Guideline- Directed Medical Therapy (GDMT) with ACEI/ARB, beta blocker, and an aldosterone antagonist, then switch to ARNI; if stable, follow with HYD/ISDN if patient has persistent class III to IV symptoms with careful blood pressure monitoring or B. Establish GDMT with ACEI/ARB, beta blocker, and an aldosterone antagonist and then proceed with HYD/ISDN if persistent class III to IV symptoms; if stable, follow with ARNI substitution for ACEI/ARB with careful blood pressure monitoring. In the absence of randomized controlled data, it is reasonable to treat an African-American patient using either approach. However, the risk for hypotension with either strategy is uncertain. The treatment decision should be determined after an informed shared decision-making discussion with the patient, indicating the uncertainty of benefit.HYD/ISDN is available as a fixed-dose combination or as individual medications. The ACC/ AHA/HFSA guideline considers either as acceptable in this context.

Conclusion

Heart Failure is a complex syndrome. The prevalence, incidence, mortality and morbidity rates reported show geographic variations, depending on the different aetiologies and clinical characteristics observed among patients. In this review we focus on the Afro Caribbean population with Heart Failure providing data review about the Heart Failure etiology based in previous Clinical Trials In addition we provide suggestions based in these Trials and our regional clinical studies that might be useful to improve our current Heart Failure Guideline-Directed Medical Therapy There is a need to understanding more the epidemiology and mechanisms of Afro Caribbean Heart Failure in order to improve the current management practices from a Caribbean perspective. At this time there are no studies on the use of ARNIs in the unique Afro Caribbean population, accordingly clinical experience studies with regards to the tolerance and safety of sacubitril/valsartan to prospectively identify adverse events and discontinuation for adverse events in patients with HFrEF are required.

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Lupine Publishers| Follow-up CT-Scan after TEVAR: is possible to prevent potential catastrophic complications?

 Lupine Publishers| Journal of Cardiology Research & Reports

Abstract

Thoracic endovascular aortic repair (TEVAR) is considered a safe and feasible technique especially in complex cases. One of the most catastrophic complications during follow up is modular disconnection. When modular disconnection occurs, end leak is massive and risk of mortality is dramatically increased. We report our findings during follow up of a 49 years male underwent ascending aorta replacement for acute Type A aortic dissection and subsequently surgical replacement of aortic arch and TEVAR due to huge enlargement of the thoraco-abdominal false lumen. Our analysis suggest.com more attention on topographic changes of the prostheses to prevent this fatal complications.

Keywords: Aortic dissection; TEVAR; Endoleak; Aortic surgery; Aneurism

Case Report

Thoracic endovascular aortic repair (TEVAR) is considered a safe and feasible technique also in complex cases with a lower morbidity and mortality rates when compared with open repair. However, follow-up CT-Scan is recommended periodically, at 6-12 months, especially when an end leak of any type has been detected. Although not frequent, modular disconnection might occur and results in one of the most catastrophic complications. In long-term follow-up studies the aneurysm sac size and native aortic morphology have been found to increase the risk for modular disconnection [1]. In the Talent Thoracic Retrospective Registry, Fattori and Co-workers reported an occurrence of modular disconnection of 1.4% [2]. In Figure 1 we found a modular disconnection in an asymptomatic 49 years old man patient during his regular follow-up CT-Scan after TEVAR. The patient underwent ascending aorta replacement for acute Type A aortic dissection five years earlier. Due to huge enlargement of the thoraces-abdominal false lumen an additional surgical treatment for the replacement of aortic arch was needed 2 years later and was achieved by means of the E-Vita Open stent-graft prosthesis Jotec Inc, Hechingen, Germany. To complete the repair, few months after aortic arch replacement, two endovascular prostheses type Relay (Bolton Medical Inc., Sunrise, FL, USA) were placed to cover the distal thoracic and abdominal aorta; stenting of superior mesenteric artery was achieved by chimney technique.

Figure 1: Volume rendering reconstruction of September 2013 CT-scan, where is evident the modular disconnection and the massive endoleak in the descending thoracic aorta.

Retrospective analysis of previous CT-Scans imaging (Figure 2) showed that even in absence of a modular disconnection there was an important endovascular prostheses displacement like a slow slip, at the expense of the overlap length. Looking carefully to the 3-year seriated CT-Scans, the topographic changes of the prostheses and their relationship with the native aortic wall are evident: in the first CT-Scan image (Figure 2A) the endovascular prostheses are next to the pulmonary artery and adherent to the native aortic wall concavity. Before the presence of the massive end leak due to modular disconnection (Figures 1), in comparison with Figure 2A, the sequences of (Figure 2B-2D) show that the prostheses were progressively dislocating toward the native aortic wall convexity. Figueroa and Co-workers, in a bioengineering study focusing on the displacement forces (DF) could demonstrate different displacements of the grafts, where the orientation of the DF acting on the prosthesis depends on aortic angulation and tortuosity. In particular, the proximal endovascular graft segment is subjected to a cranial direction vector, the mid and descending portion to sideways DF [3]. Liffman and Co-workers found that the risk of modular disconnection was higher when the seal between the graft and the aneurysm sac is blood tight, the blood pressure is high and the diameter of the graft is small in relation with a large native aneurysm. In particular, in a curved segment of the vessel, there are an “upward” and a “downward” forces displacing the modular of the endovascular grafts. To avoid dislocation of the grafts these two forces must be less than the frictional binding of two endovascular grafts that is given by the multiplication of the surface area of mutual graft intersection (πLd) x the friction coefficient (μ) and the radial force (pr) [4].

Figure 2: MPR reconstruction of follow-up CT-scans and changing in the centered line of true aortic lumen between November 2010 (A), September 2011 (B), January 2013 (C) and September 2013 (D).

With time, continuous solicitations might increase the risk of endovascular graft sliding, and marked conformational changes of prosthesis appear more frequently after 3 years [2]. In our patient, considering the cranial DF, the large aortic aneurysm sac and the use of the E-Vita Open hybrid prosthesis graft in the distal portion of the arch (considerable as a fixed surgical anastomosis), more likely the endovascular prostheses dislocation occurred with, as a catastrophic consequence, a complete modular disconnection. If prostheses modular disconnection occurred, most likely the patient will remain asymptomatic and if the time interval to the following control is too long, the risk of severe complications and rupture is considerably increased. The reported freedom from late mortality following TEVAR is not negligible and type I endoleak has been found as an independent risk factor for mortality; when the modular disconnection occurs, endoleak is massive and risk of mortality is dramatically increased [5]. At present there are no guidelines indicating the optimal mutual graft intersection area or the exact difference between the grafts diameters to be used. Besides these considerations, the aneurysmal sac size, especially in proximal segment of the descending aorta, should be taken into consideration. For our findings, probably more attention during follow-up CT-Scans should be given to the topographic changes of the prostheses and their relation with the aortic wall and other thoracic vessels. Eventually, if required, a new stent deployment can be performed to guarantee a better overlapping and to prevent potential catastrophic consequences.

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Lupine Publishers| The Gompertz Length Biased Exponential Distribution and its application to Uncensored Data

 Lupine Publishers| Journal of Biostatistics & Biometrics

Abstract

This paper proposes a generalization of the length biased exponential distribution, called the Gompertz length biased exponential (GLBE) distribution. Some of the basic properties of the proposed model were derived in minute details and model parameters estimated by the maximum likelihood estimate method. The adequacy of the model is empirically validated with the use of real - life data.

Keywords: Exponential Distribution; Length Biased; Gompertz Generalized Family Of Distribution; Quantile Function; Hazard Functions; Survival Function

Introduction

Length biased distributions are special case of the more general form known as weighted distribution [1], first introduced by [2] to model ascertainment bias and formalized in a unifying theory by [3]. Lifetime data may be modeled with several existing distributions, although the existing models are not adequate or are less representative of actual data in many situations. Therefore, the development of compound distributions that could better describe certain phenomena and make them more flexible than the baseline distribution is of great importance [4]. Thus, the choice of the model is also an important issue for reliable model parameter estimation. Some exponential distribution generalizations for modeling lifetime data due to some interesting advantages have been recently proposed [5]. In recent years many exponential distribution generalizations have been developed, such as the Marshall Olkin length biased exponential distribution [5], exponentiated exponential [6,7], generalized exponentiated moment exponential [8], extended exponentiated exponential [19], Marshall-Olkin exponential Weibull [10], Marshall-Olkin generalized exponential [5], and exponentiated moment exponential [11] distributions.

A random variable X is said to have a length biased exponential distribution with parameter \beta if its probability density function (pdf) and cumulative distribution function (cdf) is given by equation (1) and (2) respectively [12]:

Where is the scale parameter.

The survival function is given by the equation

The hazard function is

And the reversed hazard rate function is

Alzaatreh et al. [13] defined the cumulative distribution function of the Transformed-Transformer (T-X) family of distributions by;

And the corresponding probability density function by;

Morad Alizadeh et al [14] defined the cumulative distribution function and probability density function of the Gompertz Generalized family of distribution by setting

respectively. Where \theta and \gamma are additional shape parameters whose role is to vary the tail length.

Thus, we proposed a new generalization of the length biased exponential distribution called the Gompertz length biased exponential (Go-LBE) distribution. In the rest of the paper, we define the Go-LBE model and plots for different parameter values in Section 2; some of the statistical properties of the proposed Go-LBE distribution are discussed in minute details in section 3, Application of the Go-LBE distribution to a lifetime data in section 4. The concluding remark is presented in section 5.

Gompertz Length Biased Exponential (Go-LBE) Distribution

The cumulative distribution function of the

Figure 1: Graph for Go-LBE cumulative distribution function at different parameter values.

Figure 2: Graph for Go-LBE probability density function at different parameter values.

Figure 3: Graph for Go-LBE survival function at different parameter values.

Figure 4: Graph for Go-LBE hazard function at different parameter values.

Figure 5: Histogram of the fitted distributions.

Figure 6: Empirical cdf of the fitted distributions.

Some Statistical Properties of the Go-LBE Distribution

Basic properties such as the asymptotic behavior, parameter estimation and order statistics of the Go-LBE distribution are discussed in minute details.

Asymptotic Behavior

Here we critically examine the behavior of the Go-LBE model in equation (11) as x→0 and as x→∞

This indicates that the Gompertz length biased exponential distribution is unimodal. A clear observation of Figure 2 shows the Go-LBE model has only one peak. This supports our claim that the Go-LBE distribution has only one mode.

Parameter Estimation

Using maximum likelihood estimation techniques, we estimate the unknown parameter of the Go-LBE model based on a complete sample. Let X...Xn indicate a random sample of the complete Go-LBE distribution data, and then the sample’s likelihood function is given as;

We can now express the log likelihood function as;

By taking the derivative with respect toθ ,γ andβ , and fixing the outcome to zero, we have;

Solving equation (18)-(20) iteratively, will give the estimate of the parameters of the Go-LBE model.

Order Statistics

We considered a random sample denoted by from the densities of the Go-LBE distribution. Then,

The probability density function of the order statistics for the Go-LBE distribution is given as;

The Go-LBE distribution has minimum order statistics given as;

Data Analysis

Here, we provide an application of the Gompertz length biased exponential distribution by comparing the results of the model fit with that of other Gompertz- G family of distributions. The data set we employ is the uncensored strength of 1.5cm glass fibre data previously used by Bourguignon M et al. [15], Merovci F et al. [16]. This data set will be used to compare between fits of the Gompertz length biased exponential distribution (Go-LBE) with that of Gompertz-Exponential (Go-E), Gompertz-Lomax (Go-L), and, Gompertz-Weibull (Go-W). The data is presented below (Tables 1 & 2):

Table 1: Descriptive Statistics on Cancer Stem Cell Data.

Table 2: MLEs, SW, AD and K–S of parameters for Cancer Stem Cell data.

0.55, 0.74, 0.77, 0.81, 0.84, 1.24, 0.93, 1.04, 1.11, 1.13, 1.30, 1.25, 1.27, 1.28, 1.29, 1.48, 1.36, 1.39, 1.42, 1.48, 1.51, 1.49, 1.49, 1.50, 1.50, 1.55, 1.52, 1.53, 1.54, 1.55, 1.61, 1.58, 1.59, 1.60, 1.61, 1.63, 1.61, 1.61, 1.62, 1.62, 1.67, 1.64, 1.66, 1.66, 1.66, 1.70, 1.68, 1.68, 1.69, 1.70, 1.78, 1.73, 1.76, 1.76, 1.77, 1.89, 1.81, 1.82, 1.84, 1.84, 2.00, 2.01, 2.24

For all competing distributions using the strength of glass fibre data set, Table 2 shows parameter estimate and the value for the Shapiro Wilk (S-W), Anderson Darling (AD), and the Kolmogorov Smirnov (K-S) statistic (Table 3).

From Table 3, the Go-LBE has the highest log-likelihood values and the lowest AIC, CAIC, BIC and HQIC values; hence, it is chosen as the most appropriate model amongst the considered distributions.

Table 3: Log-likelihood, AIC, AICC, BIC and HQIC values of models fitted for Cancer Stem Cell data.

Conclusion

This research has successfully extended the length biased exponential distribution. Densities and basic statistical expressions were briefly derived. The performance of the proposed Gompertz length biased exponential distribution was compared to existing models in literature based on the negative log likelihood, AIC, CAIC, BIC and HQIC values. Based on the lowest criterion values, we therefore conclude that the Gompertz length biased exponential distribution is the most suitable model amongst the considered models and indeed a very competent model for describing life-time situations.

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Lupine Publishers | Heterobimetallic Aryloxides of Titanatranes with Aluminum Alkyls for Ring opening polymerization (ROP) of rac-Lactide

 Lupine Publishers | Journal of Organic and Inorganic Chemical Sciences

Abstract

The titanatrane titanium complexes were treated with Aluminum Alkyls to prepare their bimetallic derivatives (1a-4a). The compounds were confirmed by means of NMR and elemental analysis. The complexes were used as catalysts for ring opening polymerization of racemic lactide. The complexes exhibit high activity and selectivity in the polymerization process.

Abbrevations: ROP: Ring Opening Polymerization; LA: Rac-lactide

Introduction

Olefin polymerization catalysis [1a-1b] continues to be an area of considerable importance to both the academic and industrial communities, and a wide range of reports are appearing on the efficient catalyst designs and application in various catalytic systems. Recently, the work on bimetallic complexes and in particularly bimetallic oxides is gaining considerable attention due to the "cooperativity" or "communication" between neighboring repeating units [2a-2d]. Since heterometallic alkoxides are potential molecular precursors of multicomponent oxides, they are thus of interest for applications in catalysis as well as in material science. Heterometallic alkoxide derivatives have been postulated to act as catalysts in Ziegler-Natta polymerization [3a,3b] or olefin metathesis reactions, [3c] and exhibit high activity and produce polymers with different microstructure. These heterometallic complexes were also found active in nitrogen activation," but detailed characterization is lacking [4].

The main disadvantage of mononuclear catalysts is the need of large amount of MAO or expensive fluorinated borate activators to obtain adequate polymerization activity, which causes concern over the high cost of metallocene catalysts and the high ash content (Al₂O₃) of the product polymers. Consequently, there is a great need to develop new catalyst systems that can provide high catalytic activity with no need for a large amount of expensive cocatalysts. We were thus interested in designing the catalysts which can exhibit high activity in the polymerization without or with very less amount of cocatalysts. For this, we used atrane ligands which have a nitrogen atom that facilitates coordination in a chelate fashion when necessary by providing the metal with additional electronic density [5a-e]. Although there have been many reports on the complexes based on atrane ligands, application of these complexes in polymerization reactions are very limited [6a-c].

We recently reported that heterobimetallic complexes of titanium iso-propoxide and aluminum alkyl containing bis (aryloxo) ethanolamine ligand were effective as catalysts precursor for ethylene polymerization even in the absence of cocatalysts [7]. We then extended the chemistry to tris (aryloxo) amine based ligands [8]. Furthermore, we reported that titanatranes bearing terminal substituted aryloxo ligands exhibit the highest activity in ethylene polymerization [9]. To the best of our knowledge these complexes are the best catalysts for ethylene polymerization among all the titanatranes reported so far. We became interested in isolating the bimetallic complexes of titatnium bearing aryloxo terminal ligands with aluminum alkyls to understand the plausible mechanism of polymerization process and the effect of substituents on the nature of heterobimetallic complexes. In this contribution we report the isolation, structural characterization of the titanatranes bearing aryloxo terminal ligand with the aluminum alkyls and their catalytic activity in ethylene and Ring Opening Polymerization (ROP) of rac- lactide.

Results and Discussion

The titanatranes and their bimetallic derivatives are prepared as reported earlier [8]. The following complexes were confirmed by NMR and elemental analysis. The pure crystalline products were used for the polymerization process (Figure 1). There has been considerable attention on the study of ring-opening polymerization (ROP) of cyclic esters such as rac-lactide (LA) with metal complexes for the past few decades [10a-b]. Various types of metal alkoxides such as tin [11a-e], aluminum, zinc , magnesium, iron [12a-b], lanthanide [13a-c], and lithium [14] organometallic complexes have been found to be active LA polymerization catalysts, and many afford materials with controlled molecular weights and narrow molecular weight distributions. Despite the fact that some excellent initiators have been reported for the polymerization of LA, the search for new catalysts that generate well-defined polylactides remains of keen interest. The roles of the structure of metal alkoxide complexes in determining molecular weights and molecular weight distributions, as well as the polymerization pathway, are significant current research issues.

Figure 1: Bulk Polymerization of rac-Lactide (rac-LA).

Recently, Verkade et al. [15a-b] reported that several titanium alkoxides showed reasonably good catalytic activity in the bulk homopolymerization of rac-LA at 130 °C. Harada et al. [16] also reported the living polymerization of LA by a Ti chloride complex, whose chloride apparently plays the same role as an alkoxide. We thus believed it would be interesting to test heterobimetallic titanium catalysts and compare the activity and control of the molecular and physical properties of the PLA produced by mononuclear and binuclear complexes with well-defined ligand environments. Here, we describe discrete heterobimetallic titanium alkoxide/aryloxide complexes and their bimetallic derivatives for the study of the ROP of LA under bulk polymerization conditions. We also demonstrate the difference in monometallic and bimetallic catalysts towards the ROP of rac-Lactide.

Preliminary results on the use of heterobimetallic catalysts for the bulk polymerization of rac-LA are summarized for 1a-4a, are presented in Table 1. Polymerizations were performed at 130 °C with the [LA]/[Ti] ratio fixed at 300. This table reveals that all the titanium compounds catalyze LA polymerization. Moreover, it appears that chelation aluminium methyl to the tripodal tetradentate ligand significantly decreases the polydispersity index and polymer yield. However, some transesterification probably occurred during the polymerization reaction since the polydispersity indices of both PLA products were somewhat higher than expected for a controlled polymerization. The bimetallic complexes exhibit high activity and produce polylactide with high molecular weight and lower polydispersity compare to their mononuclear precursors [15].

Table 1: Ring opening polymerization (ROP) of rac -Lactide Data for Heterobimetallic complexes.

LA (2.027g) LA/Ti = 300, polymerization temperature = 130 °C, time = 20min.

The weight average molecular weight (M ), the number average molecular weight (M ), and the polydispersity index (PDI) M /M ) were determined by GPC.

Figure 2:

The preference for heterotacticity in our poly (rac-LA) are comparatively stronger for bimetallic complexes than their mononuclear precursor compounds and are similar to the previous reports by Kasperczyk et al. [17]. This may be due to the initiating alkoxide/aryloxide group which dissociate relatively easily from the titanium in bimetallic complexes than their monometallic precursors in the early stage of polymerization so that it can be utilized to initiate LA polymerization and provide a means of controlling the molecular weight by functioning as an end group. It appears that the initiating group is the highly bulky i-Pr alkoxide (in 1 and 3) or i-Pr-phenolate (2 and 4) group in monometallic, similar to the observation made by Verkade et al. [15] But the scenario in bimetallic complexes is complicated. We assume that the initiating group may be similar to the mononuclear complexes, although the insertion of lactide into Ti-O of the aryloxo arm or alkoxo arm cannot be ruled out (Figure 2) and (Table 1).

Concluding remarks

The titanatrane titanium complexes and their bimetallic derivatives exhibit high activity and selectivity in bulk polymerization of rac-Lactide. Bimetallic complexes (Ti-Al) exhibit higher activity and produces high molecular weight compared to their monometallic counterpart [5b]. This may be due to the better electronic and steric environment in bimetallic complexes. The polylactide obtained in this process is heterotactic in nature. Further investigations of mechanism in this process are on in our laboratory.

Experimental Section

General Procedures. All experimental manipulations were carried out under an atmosphere of dry nitrogen using standard Schlenk techniques or using a Vacuum Atmospheres drybox unless otherwise specified. All chemicals used were of reagent grades and were purified by standard purification procedures. Toluene (anhydrous grade, Kanto Kagaku Co., Ltd.) and n-octane (anhydrous grade, Aldrich) for polymerization were stored in a bottle in the drybox in the presence of molecular sieves (a mixture of 3A 1/16, 4A 1/8, and 13X 1/16). Polymerization grade ethylene (purity > 99.9%, Sumitomo Seika Co. Ltd.) was used as received. Toluene and AlMe3 from the commercially available methylaluminoxane [PMAO-S, 9.5wt% (Al) toluene solution, Tosoh Finechem Co.] were removed under reduced pressure (at ca. 50 °C for removing toluene and AlMe3 and then heated at >100 °C for 1 h for completion) in the drybox to give white solids. Bis (2-hydroxy-3,5-dimethylbenzyl) ethanolamine and tris(2-hydroxy-3,5-di-tert-butylbenzyl)amine were prepared according to a published procedure [18]. The titanatranes containing phenoxy terminal ligands Ti(O-2,6- iPr2C6H3){(O-2,4-Me2C6H2-6-CH2)2(OCH2CH2)N} and Ti(O-2,6- iPr2C6H3) [(O-2,4-Me2C6H2-6-CH2)3N] were prepared according to the previous report [9].

Molecular weights and molecular weight distributions for polyethylene were measured by gel permeation chromatography (Tosoh HLC- 8121GPC/HT) with a polystyrene gel column (TSK gel GMHHR-H HT x 2, 30cm *7.8mmΦ, ranging from <102 to <2.8x108 MW) at 140 °C using o-dichlorobenzene containing 0.05 w/v % 2,6-di-tert-butyl-p-cresol as eluent. The molecular weight was calculated by a standard procedure based on the calibration with standard polystyrene samples. All 1H and 13C NMR spectra were recorded on a JEOL JNMLA 400 spectrometer (399.65MHz for 1H, 100.626MHz for 13C). All deuterated NMR solvents were stored over molecular sieves under a nitrogen atmosphere in the drybox, and all chemical shifts are given in ppm and referenced to SiMe4 (TMS). All spectra were obtained in the solvent indicated at 25 °C unless otherwise specified. Elemental analyses were performed by using PE2400II Series (Perkin-Elmer Co.) [19].

Procedure for rac-Lactide Polymerization, LA bulk polymerizations were carried out by charging a stirring bar, 2.00g of LA, and then the appropriate amount of catalyst precursor to a 10ml Schlenk flask. The flask was then immersed in an oil bath at 130 °C, and after the appropriate time, the reaction was terminated by the addition of 5ml of methanol. The precipitated polymers were dissolved in a minimum amount of methylene chloride, and then, excess methanol was added. The resulting reprecipitated polymers were collected, washed with 50ml of methanol, and dried in vacuo at 50 °C for 12h [20a-b].

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Lupine Publishers | To Examine the Relationship and Strength of Alcohol-Related Intimate Partner Violence in sub-Saharan Africa

 Lupine Publishers | Journal of Research & Reviews

Abstract

Alcohol-related intimate partner violence (IPV) is a serious public health issue which has attracted a lot of research and debates. While some studies have reported the relationship between alcohol and IPV to be linear, others have reported threshold effects. While some studies have found the link to be strong, others have reported weak or no association. Using Logistic regression and meta-analysis, the relationship, strength of relationship and possible moderators of the alcohol-IPV link are investigated in ten sub-Saharan African countries. The results indicates that while alcohol consumption is associated with IPV in three of the countries, alcohol abuse was associated with IPV in the other seven countries lending support for both the linear and threshold effects in sub-Saharan Africa. The meta-analysis showed a strong association between alcohol and physical IPV while a weaker association was observed for the alcohol- sexual IPV link. Moderator analysis showed that the strength of the alcohol-IPV link in sub-Saharan Africa varies with wealth index, marital length, and marital status, and jealousy, place of residence and justification of the use of violence. The nature of moderation was different between countries. The results of this study can be applied to plan country specific and multi-faceted intervention programs.

Keywords: Alcohol; Intimate Partners; Violence; Sub-Saharan Africa

Introduction

Intimate partner violence (IPV) is defined as any physical, psy-chological or sexual harm that is caused by the actions of a present or previous intimate partner [1]. It a major public health issue and violates women's human rights [1]. Cross sectional studies have shown that 10-69 per cent of women of reproductive age experience physical violence at least once in their lifetime while 6-59% report an attempt or actual sexual violence by their intimate partners [2]. Intimate partner violence takes place in all backgrounds and among all socioeconomic, religious and cultural groups with women bearing the global burden [1]. Prevalent rates are different across countries with rates between 11-52% in developing coun-tries [3]. IPV has been reported to lead to physical injuries, loss of pregnancy and complications during pregnancy [2]. It can also result in emotional problems such as depression and suicide [2] and victims have been reported to resort to use of drugs and alcohol as a means of coping with the abuse [4].

Several risk factors such as young age, low education, occu-pation, experiencing parental violence, drug and alcohol use, con-trolling behaviour by the husband [5], justification of wife beating [6] and so on has been reported to increase the odds of IPV; of these, alcohol consumption has been consistently implicated [2,7] with the prevalence of alcohol-related IPV differing in diverse countries [2]. Although an association between alcohol and IPV has been established in previous studies, there are arguments on the role of alcohol in IPV, the effect of alcohol and the strength of the association between alcohol and IPV. Although alcohol-related IPV is a widely researched topic, only some research has been done in sub-Saharan Africa [8,9] and none has investigated the magnitude of the association across countries in Sub-Saharan Africa. The aim of this study was to determine the type of association between alcohol and IPV in sub-Saharan Africa and also examine the strength of the relationship between alcohol and IPV in Sub-Saharan Africa.

Methodology

For the quantitative study, secondary analysis and meta-analy-sis were used to analyze cross-sectional data from the demographic and health surveys of ten countries in sub-Saharan Africa (Burkina Faso, Ghana, Kenya, Liberia, Malawi, Nigeria, Sao Tome and Prin-cipe, Tanzania, Zambia and Zimbabwe). Since the aim of this re-search was to determine the relationship between alcohol and IPV in sub-Saharan Africa, a quantitative research design was adopted because it is an appropriate method for showing associations and quantifying relationships between variables [10]. In order to examine the relationship and moderators of the alcohol-IPV link in sub-Saharan Africa, a secondary analysis of previously conducted primary studies of ten countries in sub-Saharan Africa was carried out. This is the method of choice for this research as it takes a cross national perspective which requires that data from several countries in sub-Saharan Africa be analysed. Data sets for this study were also easier to access and raise little or no ethical issues as re-spondents are already made anonymous.

Data Collection Methods

This study did not collect primary data but accessed data of the demographic and health survey of ten sub-Saharan Africa countries (Burkina Faso, Ghana, Kenya, Liberia, Malawi, Nigeria, Sao Tome and Principe, Tanzania, Zambia and Zimbabwe). Large sample sizes were used with high response rate thereby ensuring that statistically significant relationships are detected. Access to the data sets was gained by requesting permission from Demographic and Health Survey (DHS). Approval from DHS was granted by email. Data was identified using the domestic violence questionnaire. The identified data sets were downloaded to the researcher's personal computer using SPSS (version 19) software. Variables in the study were identified using the DHS recode manual.

Sample/Sampling Strategy

This study used quota sampling to identify DHS surveys con-ducted between 2006 and 2011 made available by 2012 in sub-Sa-haran Africa. For this research, only countries from sub-Saharan Af-rica were included because the main independent variable (alcohol consumption) was not measured in North African countries as con-sumption is prohibited. The data for each country was the most re-cent. This was to ensure that results reflected the current strength of the alcohol-IPV link and that recommendations are made based on current evidence. All datasets included asked questions on domestic violence and covered the topic of alcohol consumption and frequency at which husband/partner gets drunk because of the fact that the focus of this study is on alcohol-related IPV.

Data Analysis

Data analysis was carried out using SPSS (version 19.0) and Revman Meta-analysis software.

Univariate Analysis: Frequencies were used to determine the prevalence of the different forms of IPV, alcohol consumption and alcohol related IPV in the ten countries included in this study.

Logistic Regression: In order to determine the type of relationship between alcohol and intimate partner violence in sub-Saharan Africa, a logistic regression of the four category alcohol measure was carried out by comparing non-drinkers to drinkers (drinkers who never got drunk, who got drunk sometimes and those who got drunk often). Results are reported as B (Standard Error), odd ratios (OR) and 95%CI for OR. A significant Wald test p-value indicates a significant difference between the categories and non-drinkers.

Meta-Analysis: In order to investigate the strength of the alcohol-IPV link in sub-Saharan Africa, a meta-analysis was car-ried out using the Revman software. This was done by comparing non-abusers (non-drinkers and drinkers who never got drunk) and abusers of alcohol (husbands who got drunk sometimes and often). Based on the assumption that effects may vary across samples and studies [11], random effects model was used. The random effects model was used in this study because of the heterogeneous nature of the studies and because this model generates results that are generalisable to the sub-Saharan Africa population. The heteroge-neity of the result was investigated using the Cochran's Q test [12]. A significant I2 shows heterogeneity among included studies with higher values indicating increased differences within study [12]. Due to the high heterogeneity between countries included in the meta-analysis, further moderation analysis was carried out.

Hierarchical Logistic Regression: Using the method described by Field [13], hierarchical logistic regression was used to study the moderator effects of the independent variables on the al- cohol-IPV link. In order to account for the complex sampling used in the DHS survey, the probability of being administered the domestic violence questionnaire and to adjust for the probability of non-re-sponse [14]; all analyses were conducted using the domestic violence sample weight.

Ethical Issues

One of the ethical issues with conducting a secondary data anal-ysis is the permission to access datasets. Approval was sought by the researcher and access was granted. The DHS also operate a no data sharing policy. To ensure data protection, memory sticks and computers were password protected to guard against unauthorised access. It is also important to confirm that the data obtained from the primary study was ethically obtained. The primary DHS study was done with the informed consent of the subjects and confidenti-ality obtained with the National ethics committees of the different countries approving the surveys. Furthermore, the datasets have been made anonymous by removing all identifier information.

Results

The study population consisted of women aged 15-49 years old and men aged 15-59 years old in ten countries in sub-Saharan Af-rica. Six hundred and eighty-two couples were interviewed in Sao Tome and Principe, 873 in Tanzania and 883 in Ghana. The largest numbers of 5566 couples were included in Nigeria while 3488 and 3051 couples participated in Burkina Faso and Malawi respectively (Figure 1). Of these numbers, the highest percentage of women were in the 25-29 years' age group with this group accounting for 22.1% of the women in Burkina Faso, 27% in Kenya, 25.8% in Malawi and 27.7% in Tanzania. For the men, 22.6%, 20.8%, 21.3% and 21.4% were in the 30-34 years' age group in Kenya, Malawi, Zimbabwe and Zambia respectively. In Ghana (19.8%), Liberia (21.5%) and Nigeria (19.8%), the highest proportion of the male participants were in the 35-39 years’ age group (Figures 2a & 2b).

Figure 1: Number of Participants in the Study.

Figure 2a: Age group of the Women

In Burkina Faso, 82.3% of the women had no education compared to 77.0% of the men. Zimbabwe and Sao Tome and Principe were found to have the highest number of couple who have had any form of education with 94.2% of the women and 99.4% of the men having a primary, secondary or higher education in Sao Tome and Principe. In Zimbabwe, only 2.7% of the women and 1.2% of the men have had no education at all. 5.2% of the women in Burkina Faso and 6.6% of the women in Tanzania reported having a second-ary education compared to 41.5% and 62.1% in Ghana and Zimbabwe respectively (Figures 3a & 3b).

Employment Status

Highest proportions of women who are unemployed were in Zimbabwe, Kenya, Zambia and Malawi with 62.3%, 61.6%, 48.3% and 42.3% of the women reporting that they have no paid employment respectively. The highest number of women who were em- ployed was reported in Ghana (88.5%), Tanzania (86%), Burkina Faso (78.6%) and Nigeria (64.4%). For the men, the highest rate of unemployment was in Zimbabwe (24.2%), Malawi (6.9%) and Liberia (6.3%) (Figure 4). When wealth index was considered, Figures 5 show that 24.5% and 22.3% of Nigerians in the study population were in the poorest and poorer wealth indexes respectively. Kenya, Sao Tome and Ghana have the highest percentages of 30.2%, 25.4% and 23.4% of the couples in the richest wealth index while 21% of the couples in Burkina Faso, 21.4% in Liberia, 21.9% in Malawi and 19.2% in Zambia were in the middle wealth index.

Figure 2b: Age Group of the Men.

Figure 3A: Education Level of the Women.

Prevalence of Intimate Partner Violence

The prevalence of emotional IPV was lowest in Burkina Faso (10.8%) and highest in Liberia (36.3%). In Ghana, 31.4% of the women reported experiencing emotional IPV while 32.3% reported same in Burkina Faso. The percentage of emotional IPV is closest in Sao Tome and Principe and Zimbabwe with 25% of the women reporting emotional IPV in Sao Tome and Principe and 25.2% in Zimbabwe. The percentage of women who reported sexual IPV ranged from as low as 1.2% in Burkina Faso to as high as 15.8% in Zimbabwe. Figures in Zambia and Malawi are closest to Zimbabwe with 15.6% of the women in Zambia and 15.4% of the women in the study population experiencing sexual violence from their husbands or partners. Zambian women reported the highest prevalence of physical IPV (44.9%) while the lowest percentage of reported physical IPV was 11.5% in Burkina Faso.

Figure 3b: Education Level of the Men.

Figure 4: Employment Rate.

Figure 5: Wealth Index of Participants in the Study.

In Kenya and Liberia, 32% and 35% of the women reported physical IPV. When all three forms of IPV were considered, prevalence rate was highest in Zambia (51.9%) followed by Liberia (50.3%) and lowest in Burkina Faso (16.7%). In general, the prevalence of physical and emotional IPV were higher than that of sexual IPV indicating that women are less likely to experience or report sexual IPV in sub-Saharan Africa (Figure 6).

Figure 6: Prevalence of Intimate Partner Violence in sub -Saharan Africa.

Prevalence of Alcohol-Related Intimate Partner Violence

Figure 7: Prevalence of Intimate Partner Violence in sub -Saharan Africa.

Figure 7 shows the prevalence of alcohol-related intimate part-ner violence among married and cohabiting women in sub-Saharan Africa. The prevalence of alcohol related physical IPV was between 21.2 to 53.9% in this study. The highest prevalence rate of alcohol-related sexual violence was 19.9% in Malawi while the lowest prevalence of 8.8% was reported in Nigeria. The prevalence of alcohol-related emotional IPV ranged from 21.3% in Burkina Faso to 43.1% in Tanzania. When all three forms of IPV were considered, prevalence rates ranged from as 16.7% in Burkina Faso to as high as 51.9% in Zambia.

Relationship between Alcohol and Intimate Partner Vi-olence

The relationship between alcohol and intimate partner violence was investigated by conducting a logistic regression of intimate partner violence (physical, sexual or emotional IPV) and the four level drinking variables. The significance of the effect of each level of the drinking variable on IPV was assessed using the Wald's test. Odd ratios (Exp B) with the 95% confidence intervals, standard error and Wald's test p values are presented. In Burkina Faso, the odds of women experiencing any form of IPV (physical, sexual or emotional IPV) is 1.7 times higher in women whose husbands never got drunk than in women whose husbands never drink while the odds of experiencing IPV is 2.23 (1.66-3.00) and 2.77 (1.82-4.21) greater in women whose husbands never got drunk compared to women whose husbands never drink in Nigeria and Sao Tome and Principe respectively. The Wald’s test shows that there is a significant difference in the odds of experiencing IPV by women whose husbands drink but never got drunk and women whose husbands never drink. The results show that in Burkina Faso, Nigeria and Sao Tome and Principe, alcohol consumption rather than alcohol abuse is associated with intimate partner violence indicating that there is a linear relationship between alcohol and IPV in these countries.

In Ghana, the odd of perpetrating intimate partner violence is 2.29 (1.66-3.16) in men who got drunk sometimes and 3.36 (2.04-5.54) in men who got drunk often compared to non-drinkers. While the OR for experience of intimate partner violence is 7.12 (4.3011.81) in women whose husbands often abuse alcohol in Kenya, the OR for IPV by women whose husbands often get drunk is 2.72 (1.81-4.08) in Liberia. In Malawi, husbands/partners who get drunk sometimes are 1.45 times more likely to abuse their partners compared to men husbands or partners who do not drink alcohol while the odds of perpetrating IPV is 4 times higher in husbands who get drunk often. Wald's test p values showed that there is no significant difference in the odds of women experiencing intimate partner violence in women whose husbands drink but never got drunk and women whose husbands never drink in Ghana, Kenya, Liberia, Malawi, Tanzania, Zambia and Zimbabwe. This indicates that it is alcohol abuse rather than drinking of alcohol that is associated with intimate partner violence. These full results are presented in Table 1 below.

Table 1: The effect of alcohol on intimate partner violence in sub

The Strength of the Alcohol-Intimate Partner Violence Link in sub-Saharan

a. Effect of Alcohol on Physical Intimate Partner Violence

Figure 8 showed the result of the meta-analysis to determine the strength of the alcohol-physical intimate partner violence in ten sub-Saharan Africa countries. A total of 22,120 participants were used in the study. Of these numbers, 6,271 were in the group of women whose husbands drink abuse alcohol while 15,849 were in the group of were in the group of women whose husbands/partners do not abuse alcohol. While 2,576 women reported experiencing physical intimate partner violence in the first group, a total of 2,698 women reported physical IPV in the other group. The results show the test for heterogeneity, I2=93% indicating a high degree of heterogeneity between the ten countries included in the analysis. The odds ratio is 2.91 (95% CI (2.24-3.79) showing that there is a strong association between alcohol and physical intimate partner violence in sub-Saharan Africa. The overall effect Z =7.96 and was statistically significant (p<0.00001). This indicates that the strength of the alcohol-physical IPV link is strong in sub-Saharan Africa.

Figure 8: Effect of Alcohol on Physical IPV in SSA.

b. Effect of Alcohol on Sexual Intimate Partner Violence

The meta-analysis to determine the effect of alcohol on sexual IPV is presented in Figure 9. A total of 22,104 women were included in the study. 6,266 were in the alcohol abuse group while 15,838 were in the non- alcohol abuse group. Of the 6,266 women in the alcohol abuse group, 971 reported experiencing sexual IPV while 1,006 reported sexual IPV in the non-alcohol abuse group. The above results show an I2 value of 70% indicating heterogeneity between studies. An OR of 2.15 (95%CI=1.78-2.60) means that women in sub-Saharan Africa are two times more likely to report sexual violence when their husbands/partners abuse alcohol than when they do not. An odd ratio of 2.15 shows that there is a small effect size for the alcohol-sexual violence link in sub-Saharan Africa. The overall effect Z=7.87 (0.00001) is highly significant indicating that the effect of alcohol on IPV is highly significant. These results imply that the strength of the alcohol-sexual IPV link is weak in sub-Saharan Africa.

Figure 9: Effect of Alcohol on Sexual Intimate Partner Violence in sub-Saharan Africa.

c. Effect of Alcohol on Emotional Intimate Partner Violence

A total of 22,112 respondents took part in the study to deter-mine the effect of alcohol on emotional intimate partner violence. A total of 5,151 participants reported experiencing emotional intimate partner violence. Of this number, 2,182 reported that their husbands abuse alcohol while 2,969 reported that their husbands never abuse alcohol. The result of the meta-analysis is presented in Figure 10 below. The results above show that women whose husbands abuse alcohol are 2.36 times more likely to report emotional intimate partner violence in sub-Saharan Africa OR=2.36 (95%1.96-2.83). This means that there is a moderate effect size for the association between alcohol and emotional intimate partner violence in sub-Saharan Africa. An I2 value of 85% indicates high heterogeneity between studies. The overall effect Z was highly significant (Z=9.15, p<0.00001)

Discussion

Prevalence of Intimate Partner Violence in SSA

In this study, the prevalence of physical intimate partner violence is 44.9% in Zambia, 28.9% in Zimbabwe and 19.9% in Mala wi. These values are similar to the 45%, 28% and 20% reported by Hindin et al. [15] for Zambia, Zimbabwe and Malawi respectively. On the other hand, the 32% and 32.2% prevalence rates reported for Kenya and Tanzania herein are lower than the 39% reported by Hindin et al. [15] and the 48% observed by Tumwesigye et al. [16] for Uganda which is a neighboring East African country. The percentage of physical IPV in other countries in this study ranged from between 11.5% in Burkina Faso to 28.5% in Sao Tome and Principe. While some of these rates are similar to figures reported in other sub-Saharan African countries, others are less. For instance, the 28.5% prevalence reported here is similar to the 29% reported for Rwanda [15]. However, the 11.5% reported for Burkina Faso is lower than rates reported anywhere in sub-Saharan Africa but similar to the 12% reported for Haiti [3]. These differences in prevalence rates may be as a result of the questions used to assess physical IPV.

Figure 10: Effect of Alcohol on Emotional Intimate Partner Violence in SSA.

This study asked respondents whether husband/partner has ever threatened or attacked them with a gun/knife or other weapons while the Hindin et al. [15] separated this question into threat and actual attack. Combining these two questions would mean that women who have experienced both threat and the act can only give one response to both questions leading to the lower rates obtained in this study. In this study, 16.1% of women in Nigeria re-ported physical IPV. This is slightly higher than the 15% reported by Antai et al. [17] using the same study data. While the Antai et al. [17] study used the individual recode which is a sample of legally married women, the present study used a sample of currently married/cohabiting women. This is consistent with findings that the prevalence of IPV is higher in currently married than legally married women [15]. In spite of these observed differences in the prevalence of physical IPV in some sub-Saharan African countries in this study, the observed prevalence of 11.5 to 44.9% in this study is consistent with that reported in other studies [2,3,16-18].

Apart from physical IPV, the prevalence of sexual and emotion-al IPV was also examined. Results indicated that the rates of sexual IPV ranged from 1.2% in Burkina Faso to 15.8% in Zimbabwe. These rates are similar to the 3 to 16% prevalence rates reported in existing literatures for sub-Saharan Africa [15,17]. The prevalence of emotional IPV in this study ranged from 10.8% in Burkina Faso to 36.3% in Liberia. This is higher than the prevalence rates of 10.4 to 22.7% reported elsewhere [19]. When all three forms of IPV were considered, the prevalence rates increased for all ten countries and were higher than that reported in previous studies. For example, Hindin et al. [15] reported a prevalence of 45% for Zambia in their studies while this study shows a prevalence of 51.9% for Zambia when all forms of IPV were considered. It can thus be argued that studies investigating only one form of IPV result in an under estimation of the magnitude of IPV. Overall, the prevalence of sexual violence in this study was consistently lower than that reported for physical and emotional violence across all countries included in this work.

Prevalence of Alcohol-Related Intimate Partner Violence

The prevalence of alcohol IPV was between 29.9% to 60.1% when of physical, sexual or emotional IPV is considered. These rates are higher than the 33.9 to 49.5% reported for countries in sub-Saharan Africa [15,16] and 10.5 to 55% reported elsewhere [2]. However, this is lower than the 65% rate reported in South Africa [2]. The higher rates reported in this study is as a result of the fact that this study investigated the experience of all three forms of IPV indicating that previous studies may have been subject to an under reporting of prevalence rates of IPV as only physical or sexual IPV are usually investigated. The lower prevalence of alcohol-related IPV in this study compared to the 65% prevalence reported in South Africa can be explained by the fact that while the present study investigated the prevalence of women ever experiencing alcohol-related IPV, the South African study reported prevalence for the past twelve months.

Following the same trend as IPV, it is possible that the occur-rence of current alcohol-related violence may be higher than past occurrence. Women who have experienced alcohol-related violence may recall these incidents more since they are more recent than if they took place a long time ago. Another possible explanation for this is that in South Africa, it is believed that alcohol causes aggres-sion and this has led men to drink in order to carry out violent acts [2] thereby increasing the rate of alcohol-related violence in South Africa compared to other sub-Saharan African countries.

The Relationship between Alcohol and Intimate Partner Violence in SSA

In all ten countries, alcohol was consistently linked to women's experience of intimate partner violence with the nature of the re-lationship varying across different countries. The findings of this study showed that in seven out of the eleven countries (Ghana, Ken-ya, Liberia, Malawi, Tanzania, Zambia and Zimbabwe), there was no significant difference in the odds of experiencing IPV in women whose husbands/partners never consumed alcohol and those whose husbands/partners never got drunk. This is consistent with the findings in several literatures [2,3,16]. This can be explained by the fact that for alcohol to significantly increase the odds of perpetrating intimate partner violence, alcohol consumption has to surpass a particular amount or rate of consumption.

This explanation is consistent with that put forward by propo-nents of the threshold effect who argue that it is not alcohol con-sumption per se that contributes to intimate partner violence but alcohol abuse. Conversely, in Burkina Faso, Nigeria and Sao Tome and Principe, women whose husbands consumed alcohol but never got drunk were significantly more likely to experience any of physical, sexual or emotional intimate partner violence than women whose husbands never consumed alcohol. This is similar to the report of Bangdiwala et al. [20] who reported a strong linear re-lationship for the alcohol-IPV link. These results are in agreement with the justification put forward by the proponents of the linear effect conceptualization who maintain that alcohol abuse increases the odds of intimate partner violence and that these odds increases with increase in the quantity of alcohol consumed.

In Kenya alone, the odds of alcohol increasing the odds of in-timate partner violence only reached statistical significance in the women whose husbands/partners often got drunk. This indicates that in Kenya, it is the frequency of alcohol abuse and not abuse alone that contributes to the alcohol-IPV link. Drawing from the multiple threshold conceptualisation [21], it is possible that the likelihood of experiencing intimate partner violence in Kenya is already very high that alcohol consumption or less frequent alcohol abuse does not significantly contribute to an increased odd of intimate partner violence while more frequent alcohol abuse may increase the frequency and severity of intimate partner violence in this sample thereby increasing the likelihood of intimate partner violence in this group.

The findings of this study support both the linear and threshold conceptualisation of the alcohol-IPV link. This suggests that the type of relationship between alcohol and intimate partner violence varies across countries in sub-Saharan Africa with most countries showing a threshold effect. This observed difference could be as a result of differences in drinking pattern. In the seven countries where threshold effects were observed, large percentages (86.3 to 99.1%) of men who drink get drunken showing drinking cultures that are supportive of alcohol abuse.

Strength of Alcohol-Intimate Partner Violence Link in SSA

A meta-analysis of the ten countries included in this study showed an odds ratio of 2.91 (95%CI, 2.24-3.39) for physical IPV which shows that women whose husbands abuse alcohol are almost thrice as likely to experience IPV than women whose husbands do not abuse alcohol. This shows a strong association between alcohol and intimate partner violence in sub-Saharan Africa. This is consistent with the strong association reported in a meta-analysis by Gil-Gonzalez et al. [22]. The strong association between alcohol and physical IPV in this study can be explained by the culture of masculinity in sub-Saharan Africa. It is considered masculine for men to drink and it is also seen as a thing of pride for a man to be feared and respected by his wife. It is also generally acceptable for men to physically reprimand their wives if they feel that the women have erred in anyway.

On the other hand, a small but significant relationship was observed for alcohol and sexual intimate partner violence in this study. This is similar to the report of Tang and Lai [23] who report-ed a significant but weak association between alcohol abuse and sexual intimate partner violence. This weak association could be as a result of the fact that in African society, sex is considered a private matter not to be discussed with strangers. There is also shame as-sociated with being raped and made to perform unwanted sexual acts and women are often blamed for it and this may result in under reporting. Women may also consider that being made to perform any form of sexual act is acceptable so long as it is within a marriage or committed relationship and may not consider this as IPV. For example, it is commonly believed in Africa that a man cannot rape his wife. Hence forced sexual intercourse in a marriage is not considered rape but seen as a normal part of the relationship. When the severity of intimate partner. Based on the results from this re-search, it can be argued that the strength of the alcohol-IPV link in sub-Saharan Africa depends on the type of IPV measured.

Conclusion

The purpose of this research work is to identify the relationship, strength of relationship between alcohol and intimate partner violence in sub-Saharan Africa. Results of this study show that alcohol is consistently associated with intimate partner violence in all ten countries included in this study with the strength of this relationship depending on the form of intimate partner violence. While a linear relationship was found between alcohol and intimate partner violence in Burkina Faso, Nigeria and Sao Tome and Principe, a threshold effect was observed in the remaining seven countries with the odds of alcohol-related intimate partner violence increasing with increase in alcohol consumption and alcohol abuse. The strength of the alcohol-intimate partner violence link was also found to be dependent on the effects of other variables in some countries with the direction of moderation different in the countries where these moderation effects are present.

The results also show that when the three forms of IPV were measured, the prevalence of both IPV and alcohol-related IPV were higher than that of existing literatures suggesting that studies of IPV estimating only one or two forms of IPV are subject to under es-timation of the magnitude of his huge public health problem. These findings have potentially important implications for public health promotion, policy and practice. The implication of the findings of this research is that interventions for tackling alcohol-related IPV should be multifaceted and should address behavioural, cultural and social change

Study Limitations

Despite the above strengths, the result of this study should be interpreted bearing in mind several limitations. First, because the information on problem drinking was provided by women, there is the possibility of misclassification bias. Responses were not taken from men about their drinking and IPV perpetration and this would have been valuable in corroborating the women report. There is also a tendency for recall bias as IPV may have taken place at a different time from alcohol abuse. Classification of drinking as sometimes or often drunk makes the report subjective rather than objective and may have led to results showing a stronger relationship between alcohol and IPV in sub-Saharan Africa. This is because studies have shown that studies assessing alcohol abuse is more associated with IPV than those measuring quantities [24].

Even though the results of this research are to a great extent consistent with those reported for community samples in other studies, it cannot be generalised to clinical samples of alcohol abusers or IPV perpetrators because studies have shown that the magnitude of the association between alcohol and IPV is stronger in clinical than community samples [24]. Finally, because this study analysed data from cross sectional studies which are ecological in nature, it is difficult to know if problem drinking took place before IPV or vice versa. It is possible that perpetrators of IPV are more likely to misuse alcohol or that individual's use alcohol to cope with stressful life events hence causality cannot be assumed.

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