Some puzzling situations in the onset, occurrence and future of coronary heart disease in developed and developing populations, particularly such in sub-Saharan Africa

Epidemiology and the Magnitude of Coronary Artery Disease and Acute Coronary Syndrome: A Narrative Review

BACKGROUND

Coronary Artery Disease (CAD) is the foremost single cause of mortality and loss of Disability Adjusted Life Years (DALYs) globally. A large percentage of this burden is found in low and middle income countries. This accounts for nearly 7 million deaths and 129 million DALYs annually and is a huge global economic burden.

OBJECTIVE

To review epidemiological data of coronary artery disease and acute coronary syndrome in low, middle and high income countries.

METHODS

Keyword searches of Medline, ISI, IBSS and Google Scholar databases. Manual search of other relevant journals and reference lists of primary articles.

RESULTS

Review of the results of studies reveals the absolute global and regional trends of the CAD and the importance and contribution of CAD for global health. Data demonstrates which region or countries have the highest and lowest age-standardized DALY rates and what factors might explain these patterns. Results also show differences among the determinants of CAD, government policies, clinical practice and public health measures across the various regions of world.

CONCLUSION

CAD mortality and prevalence vary among countries. Estimation of the true prevalence of CAD in the population is complex. A significant number of countries have not provided data, the estimation of the exact figures for epidemiological data is a barrier. The incidence of CAD continues to fall in developed countries over the last few decades and this may be due to both effective treatment of the acute phase and improved primary and secondary preventive measures. Developing countries show considerable variability in the incidence of CAD. The globalization of the Western diet and increased sedentary lifestyle will have a dramatic influence on the progressive increase in the incidence of CAD in these countries.

Provider-perceived barriers to diagnosis and treatment of acute coronary syndrome in Tanzania: a qualitative study

Background

The incidence of acute coronary syndrome (ACS) is growing across sub-Saharan Africa and many healthcare systems are ill-equipped for this growing burden. Evidence suggests that healthcare providers may be underdiagnosing and undertreating ACS, leading to poor health outcomes. The goal of this study was to examine provider perspectives on barriers to ACS care in Tanzania in order to identify opportunities for interventions to improve care.

Methods

Semistructured in-depth interviews were conducted with physicians and clinical officers from emergency departments and outpatient departments in northern Tanzania. Thematic analysis was conducted using an iterative cycle of coding and consensus building.

Results

The 11 participants included six physicians and five clinical officers from health centers, community hospitals and one referral hospital. Providers identified barriers related to providers, systems and patients. Provider-related barriers included inadequate training regarding ACS and poor application of textbook-based knowledge. System-related barriers included lack of diagnostic equipment, unavailability of treatments, referral system delays, lack of data regarding disease burden, absence of locally relevant guidelines and cost of care. Patient-related barriers included inadequate ACS knowledge, inappropriate healthcare-seeking behavior and non-adherence.

Conclusions

This study identified actionable barriers to ACS care in northern Tanzania. Multifaceted interventions are urgently needed to improve care.

M235T polymorphism in the angiotensinogen gene and cardiovascular disease: An updated meta-analysis of 39 case-control comparisons

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Perceptions of chest pain and healthcare seeking behavior for chest pain in northern Tanzania: A community-based survey

Background

Little is known about community perceptions of chest pain and healthcare seeking behavior for chest pain in sub-Saharan Africa.

Methods

A two-stage randomized population-based cluster survey with selection proportional to population size was performed in northern Tanzania. Self-identified household healthcare decision-makers from randomly selected households were asked to list all possible causes of chest pain in an adult and asked where they would go if an adult household member had chest pain.

Results

Of 718 respondents, 485 (67.5%) were females. The most commonly cited causes of chest pain were weather and exercise, identified by 342 (47.6%) and 318 (44.3%) respondents. Two (0.3%) respondents identified ‘heart attack’ as a possible cause of chest pain. A hospital was selected as the preferred healthcare facility for an adult with chest pain by 277 (38.6%) respondents. Females were less likely to prefer a hospital than males (OR 0.65, 95% CI 0.47–0.90, p = 0.008).

Conclusions

There is little community awareness of cardiac causes of chest pain in northern Tanzania, and most adults reported that they would not present to a hospital for this symptom. There is an urgent need for educational interventions to address this knowledge deficit and guide appropriate care-seeking behavior.

Fibrinogen concentration and its role in CVD risk in black South Africans – effect of urbanisation

The aim of this study was to investigate correlates of fibrinogen concentration in black South Africans, as well as its association with cardiovascular disease (CVD) risk and whether urbanisation influences this association. A total of 1,006 rural and 1,004 urban black South Africans from the PURE study were cross-sectionally analysed. The association of fibrinogen with CVD risk was determined by investigating the association of fibrinogen with other CVD risk markers as well as with predicted CVD risk using the Reynolds Risk score. The rural group had a significantly higher fibrinogen concentration than the urban group, despite higher levels of risk factors and increased predicted CVD risk in the urban group. Increased levels of CVD risk factors were, however, still associated with increased fibrinogen concentration. Fibrinogen correlated significantly, but weakly, with overall predicted CVD risk. This correlation was stronger in the urban than in the rural group. Multiple regression analysis showed that a smaller percentage of the variance in fibrinogen is explained by the traditional CVD risk factors in the rural than in the urban group. In conclusion, fibrinogen is weakly associated with CVD risk (predicted overall risk as well with individual risk factors) in black South Africans, and is related to the degree of urbanisation. Increased fibrinogen concentration, in black South Africans, especially in rural areas, is largely unexplained, and likely not strongly correlated with traditional CVD-related lifestyle and pathophysiological processes. This does, however, not exclude the possibility that once increased, the fibrinogen concentration contributes to future development of CVD.

Socioeconomic Factors and Severity of Coronary Artery Disease in Patients Undergoing Coronary Angiography: A Multicentre Study of Arabian Gulf States

INTRODUCTION

Coronary artery disease (CAD) is a leading cause of death worldwide. The association of socioeconomic status with CAD is supported by numerous epidemiological studies. Whether such factors also impact the number of diseased coronary vessels and its severity is not well established.

MATERIALS AND METHODS

We conducted a prospective multicentre, multi-ethnic, cross sectional observational study of consecutive patients undergoing coronary angiography (CAG) at 5 hospitals in the Kingdom of Saudi Arabia and the United Arab Emirates. Baseline demographics, socioeconomic, and clinical variables were collected for all patients. Significant CAD was defined as ≥70% luminal stenosis in a major epicardial vessel. Left main disease (LMD) was defined as ≥50% stenosis in the left main coronary artery. Multi-vessel disease (MVD) was defined as having >1 significant CAD.

RESULTS

Of 1,068 patients (age 59 ± 13, female 28%, diabetes 56%, hypertension 60%, history of CAD 43%), 792 (74%) were from urban and remainder (26%) from rural communities. Patients from rural centres were older (61 ± 12 vs 58 ± 13), and more likely to have a history of diabetes (63 vs 54%), hypertension (74 vs 55%), dyslipidaemia (78 vs 59%), CAD (50 vs 41%) and percutaneous coronary intervention (PCI) (27 vs 21%). The two groups differed significantly in terms of income level, employment status and indication for angiography. After adjusting for baseline differences, patients living in a rural area were more likely to have significant CAD (adjusted OR 2.40 [1.47, 3.97]), MVD (adjusted OR 1.76 [1.18, 2.63]) and LMD (adjusted OR 1.71 [1.04, 2.82]). Higher income was also associated with a higher risk for significant CAD (adjusted OR 6.97 [2.30, 21.09]) and MVD (adjusted OR 2.49 [1.11, 5.56]), while unemployment was associated with a higher risk of significant CAD (adjusted OR 2.21, [1.27, 3.85]).

CONCLUSION

Communal and socioeconomic factors are associated with higher odds of significant CAD and MVD in the group of patients referred for CAG. The underpinnings of these associations (e.g. pathophysiologic factors, access to care, and system-wide determinants of quality) require further study.

Cardiovascular Diseases and Risk-Factor Burden in Urban and Rural Communities in High-, Middle-, and Low-Income Regions of China: A Large Community-Based Epidemiological Study

Background

Most cardiovascular diseases occur in low‐ and middle‐income regions of the world, but the socioeconomic distribution within China remains unclear. Our study aims to investigate whether the prevalence of cardiovascular diseases differs among high‐, middle‐, and low‐income regions of China and to explore the reasons for the disparities.

Methods and Results

We enrolled 46 285 individuals from 115 urban and rural communities in 12 provinces across China between 2005 and 2009. We recorded their medical histories of cardiovascular diseases and calculated the INTERHEART Risk Score for the assessment of cardiovascular risk‐factor burden, with higher scores indicating greater burden. The mean INTERHEART Risk Score was higher in high‐ and middle‐income regions than in low‐income regions (9.47, 9.48, and 8.58, respectively, P<0.0001). By contrast, the prevalence of total cardiovascular disease (stroke, ischemic heart disease, and other heart diseases that led to hospitalization) was lower in high‐ and middle‐income regions than in low‐income regions (7.46%, 7.42%, and 8.36%, respectively, P_trend=0.0064). In high‐ and middle‐income regions, urban communities have higher INTERHEART Risk Score and higher prevalent rate than rural communities. In low‐income regions, however, the prevalence of total cardiovascular disease was similar between urban and rural areas despite the significantly higher INTERHEART Risk Score for urban settings.

Conclusions

We detected an inverse trend between risk‐factor burden and cardiovascular disease prevalence in urban and rural communities in high‐, middle‐, and low‐income regions of China. Such asymmetry may be attributed to the interregional differences in residents’ awareness, quality of healthcare, and availability and affordability of medical services.

Cardiovascular risk and events in 17 low-, middle-, and high-income countries

BACKGROUND

More than 80% of deaths from cardiovascular disease are estimated to occur in low-income and middle-income countries, but the reasons are unknown.

METHODS

We enrolled 156,424 persons from 628 urban and rural communities in 17 countries (3 high-income, 10 middle-income, and 4 low-income countries) and assessed their cardiovascular risk using the INTERHEART Risk Score, a validated score for quantifying risk-factor burden without the use of laboratory testing (with higher scores indicating greater risk-factor burden). Participants were followed for incident cardiovascular disease and death for a mean of 4.1 years.

RESULTS

The mean INTERHEART Risk Score was highest in high-income countries, intermediate in middle-income countries, and lowest in low-income countries (P<0.001). However, the rates of major cardiovascular events (death from cardiovascular causes, myocardial infarction, stroke, or heart failure) were lower in high-income countries than in middle- and low-income countries (3.99 events per 1000 person-years vs. 5.38 and 6.43 events per 1000 person-years, respectively; P<0.001). Case fatality rates were also lowest in high-income countries (6.5%, 15.9%, and 17.3% in high-, middle-, and low-income countries, respectively; P=0.01). Urban communities had a higher risk-factor burden than rural communities but lower rates of cardiovascular events (4.83 vs. 6.25 events per 1000 person-years, P<0.001) and case fatality rates (13.52% vs. 17.25%, P<0.001). The use of preventive medications and revascularization procedures was significantly more common in high-income countries than in middle- or low-income countries (P<0.001).

CONCLUSIONS

Although the risk-factor burden was lowest in low-income countries, the rates of major cardiovascular disease and death were substantially higher in low-income countries than in high-income countries. The high burden of risk factors in high-income countries may have been mitigated by better control of risk factors and more frequent use of proven pharmacologic therapies and revascularization. (Funded by the Population Health Research Institute and others.).

Acute myocardial infarction in sub-Saharan Africa: the need for data

BACKGROUND

Trends in the prevalence of acute myocardial infarction in sub-Saharan Africa have not been well described, despite growing recognition of the increasing burden of cardiovascular disease in low- and middle-income countries. The aim of this systematic review was to describe the prevalence of acute myocardial infarction in sub-Saharan Africa.

METHODS

We searched PubMed, EMBASE, Global Health Archive, CINAHL, and Web of Science, and conducted reference and citation analyses. Inclusion criteria were: observational studies, studies that reported incidence or prevalence of acute myocardial infarction, studies conducted in sub-Saharan Africa, and studies that defined acute myocardial infarction by EKG changes or elevation of cardiac biomarkers. Studies conducted prior to 1992 were excluded. Two independent reviewers analyzed titles and abstracts, full-texts, and references and citations. These reviewers also performed quality assessment and data extraction. Quality assessment was conducted with a validated scale for observational studies.

FINDINGS

Of 2292 records retrieved, seven studies met all inclusion criteria. These studies included a total of 92,378 participants from highly heterogeneous study populations in five different countries. Methodological quality assessment demonstrated scores ranging from 3 to 7 points (on an 8-point scale). Prevalence of acute myocardial infarction ranged from 0.1 to 10.4% among the included studies.

INTERPRETATION

There is insufficient population-based data describing the prevalence of acute myocardial infarction in sub-Saharan Africa. Well-designed registries and surveillance studies that capture the broad and diverse population with acute myocardial infarction in sub-Saharan Africa using common diagnostic criteria are critical in order to guide prevention and treatment strategies.

REGISTRATION

Registered in International Prospective Register of Systematic Reviews (PROSPERO) Database #CRD42012003161.

Association of blood lipids, creatinine, albumin, and CRP with socioeconomic status in Malawi

BACKGROUND

The objective of these analyses is to document the relationship between biomarker-based indicators of health and socioeconomic status (SES) in a low-income African population where the cumulative effects of exposure to multiple stressors on physiological functions and health in general are expected to be highly detrimental for the well-being of individuals.

METHODS

Biomarkers were collected subsequent to the 2008 round of the Malawi Longitudinal Study of Families and Health (MLSFH), a population-based study in rural Malawi, including blood lipids (total cholesterol, LDL, HDL, ratio of total cholesterol to HDL), biomarkers of renal and liver organ function (albumin and creatinine) and wide-range C-reactive protein (CRP) as a non-specific biomarker for inflammation. These biomarkers represent widely used indicators of health that are individually or cumulatively recognized as risk factors for age-related diseases among prime-aged and elderly individuals. Quantile regressions are used to estimate the age-gradient and the within-day variation of each biomarker distribution. Differences in biomarker levels by socioeconomic status are investigated using descriptive and multivariate statistics.

RESULTS

Overall, the number of significant associations between the biomarkers and socioeconomic measures is very modest. None of the biomarkers significantly varies with schooling. Except for CRP where being married is weakly associated with lower risk of having an elevated CRP level, marriage is not associated with the biomarkers measured in the MLSFH. Similarly, being Muslim is associated with a lower risk of having elevated CRP but otherwise religion does not predict being in the high-risk quartiles of any of the MLSFH biomarkers. Wealth does not predict being in the high-risk quartile of any of the MLSFH biomarkers, with the exception of a weak effect on creatinine. Being overweight or obese is associated with increased likelihood of being in the high-risk quartile for cholesterol, Chol/HDL ratio, and LDL.

CONCLUSIONS

The results provide only weak evidence for variation of the biomarkers by socioeconomic indicators in a poor Malawian context. Our findings underscore the need for further research to understand the determinants of health outcomes in a poor low-income context such as rural Malawi.

Urbanization, ethnicity and cardiovascular risk in a population in transition in Nakuru, Kenya: a population-based survey

Background

Cardiovascular disease (CVD) is the leading cause of death among older people in Africa. This study aimed to investigate the relationship of urbanization and ethnicity with CVD risk markers in Kenya.

Methods

A cross-sectional population-based survey was carried out in Nakuru Kenya in 2007-2008. 100 clusters of 50 people aged ≥50 years were selected by probability proportionate to size sampling. Households within clusters were selected through compact segment sampling. Participants were interviewed by nurses to collect socio-demographic and lifestyle information. Nurses measured blood pressure, height, weight and waist and hip circumference. A random finger-prick blood sample was taken to measure glucose and cholesterol levels.

Hypertension was defined as systolic blood pressure (SBP) ≥140 mm Hg, or diastolic blood pressure (DBP) ≥90 mm Hg or current use of antihypertensive medication; Diabetes as reported current medication or diet control for diabetes or random blood glucose level ≥11.1 mmol/L; High cholesterol as random blood cholesterol level ≥5.2 mmol/L; and Obesity as Body Mass Index (BMI)≥30 kg/m².

Results

5010 eligible subjects were selected, of whom 4396 (88%) were examined. There was a high prevalence of hypertension (50.1%, 47.5-52.6%), obesity (13.0%, 11.7-14.5%), diabetes (6.6%, 5.6-7.7%) and high cholesterol (21.1%, 18.6-23.9). Hypertension, diabetes and obesity were more common in urban compared to rural groups and the elevated prevalence generally persisted after adjustment for socio-demographic, lifestyle, obesity and cardiovascular risk markers. There was also a higher prevalence of hypertension, obesity, diabetes and high cholesterol among Kikuyus compared to Kalenjins, even after multivariate adjustment. CVD risk markers were clustered both across the district and within individuals. Few people received treatment for hypertension (15%), while the majority of cases with diabetes received treatment (68%).

Conclusions

CVD risk markers are common in Kenya, particularly in urban areas. Exploring differences in CVD risk markers between ethnic groups may help to elucidate the epidemiology of these conditions.

Physical activity and blood lipids in rural and urban Tanzanians

BACKGROUND

Physical inactivity and raised blood lipids are two powerful risk factors for coronary heart disease (CHD). Incidence and mortality from CHD are expected to increase in developing countries. However, studies on the prevalence of cardiovascular risk factors in Africa are rare. In this study we examined the level of physical activity and serum lipids in rural and urban Tanzanians.

METHODS

Rural and urban inhabitants, n=985, mean age 43.8 years [SD, +/-8.9] were investigated. Physical activity level (PAL) was assessed by an interview-administered questionnaire and blood samples were collected and analysed for serum lipids.

RESULTS

The rural population (n=501) reported a substantially higher PAL than the urban population (n=484). They also had significantly lower mean weight, body mass index (BMI), T-cholesterol, LDL-cholesterol, and HDL-cholesterol, T-cholesterol/HDL-cholesterol ratio, triglycerides and Apolipoprotein A-1.

CONCLUSION

This study demonstrates that the urban Tanzanians have a considerably lower physical activity level and a more unfavourable lipid pattern than rural Tanzanians. These findings underline the importance of undertaking preventive measures to counter the increasing incidence of CHD in urban African populations.

Agrarian diet and diseases of affluence--do evolutionary novel dietary lectins cause leptin resistance?

BACKGROUND

The global pattern of varying prevalence of diseases of affluence, such as obesity, cardiovascular disease and diabetes, suggests that some environmental factor specific to agrarian societies could initiate these diseases.

PRESENTATION OF THE HYPOTHESIS

We propose that a cereal-based diet could be such an environmental factor. Through previous studies in archaeology and molecular evolution we conclude that humans and the human leptin system are not specifically adapted to a cereal-based diet, and that leptin resistance associated with diseases of affluence could be a sign of insufficient adaptation to such a diet. We further propose lectins as a cereal constituent with sufficient properties to cause leptin resistance, either through effects on metabolism central to the proper functions of the leptin system, and/or directly through binding to human leptin or human leptin receptor, thereby affecting the function.

TESTING THE HYPOTHESIS

Dietary interventions should compare effects of agrarian and non-agrarian diets on incidence of diseases of affluence, related risk factors and leptin resistance. A non-significant (p = 0.10) increase of cardiovascular mortality was noted in patients advised to eat more whole-grain cereals. Our lab conducted a study on 24 domestic pigs in which a cereal-free hunter-gatherer diet promoted significantly higher insulin sensitivity, lower diastolic blood pressure and lower C-reactive protein as compared to a cereal-based swine feed. Testing should also evaluate the effects of grass lectins on the leptin system in vivo by diet interventions, and in vitro in various leptin and leptin receptor models. Our group currently conducts such studies.

IMPLICATIONS OF THE HYPOTHESIS

If an agrarian diet initiates diseases of affluence it should be possible to identify the responsible constituents and modify or remove them so as to make an agrarian diet healthier.

A genome wide quantitative trait linkage analysis for serum lipids in type 2 diabetes in an African population

Lipid abnormalities are strongly linked with coronary heart disease and are common in type 2 diabetes. However, little is known about the genetic determinants of serum lipids in African populations. An autosomal genome scan was performed for linkage to five plasma lipid phenotypes (total cholesterol, triglycerides (TG), HDL-cholesterol (HDL-C), LDL-cholesterol (LDL-C) and VLDL-cholesterol (VLDL-C)) in the Africa-America Diabetes Mellitus (AADM) study. Two hundred and ninety-five affected sibling pairs with type 2 diabetes mellitus enrolled from Ghana and Nigeria were genotyped for 390 microsatellite markers with an average inter-marker distance of 9cM. Multipoint variance components linkage analysis showed that HDL-C had a LOD score of 4.34 near marker D7S3061 and 3.00 near marker D7S513. Some clustering of linkage evidence to several lipid phenotypes was observed on chromosomes 5 (LDL-C, total cholesterol, VLDL-C), chromosome 7 (HDL-C, TG) and chromosome 19 (total cholesterol, LDL-C, TG). Principal component analysis of the five phenotypes yielded two factors, one (TG, HDL-C and VLDL) of which was linked to QTLs on chromosomes 2, 5 and 7, while the other (total cholesterol and LDL-C) was linked to a different set of QTLs on chromosomes 2, 5 and 18. Several of these regions have been reported to be linked to lipids in other studies. Follow up investigations are warranted in view of the central role serum lipids play in the aetiopathogenesis of cardiovascular disease.