Alcohol consumption and cardiovascular disease risk in an African population in transition: The Prospective Urban and Rural Epidemiology (PURE) study

Objective: There is evidence showing a cardioprotective effect of light to moderate alcohol consumption in many populations. Whether alcohol consumption reduces cardiovascular disease (CVD) risk in an African population remains unclear. This study therefore assessed the associations between alcohol consumption (using reported alcohol intake and biological alcohol consumption markers) and CVD risk factors in an African population in transition. Design: This cross-sectional epidemiological survey is part of the South African segment of the international 12-year Prospective Urban and Rural Epidemiology (PURE) study in which the health transition in urban and rural subjects is investigated. Setting: A rural and urban site in the North West Province of South Africa. Subjects: A total of 2 010 apparently healthy African volunteers (35 years and older) were recruited from a sample of 6 000 randomly selected households. Methods: Alcohol consumption was assessed by a validated quantitative food frequency questionnaire (QFFQ) and two biological markers, percentage serum carbohydrate-deficient transferrin (%CDT) and gamma-glutamyl transferase (GGT). The cardiovascular risk factors included in this analysis were serum lipids and blood pressure. Complete data of 1 763 and 1 878 participants were available for %CDT and GGT respectively. The subjects were divided into quartiles on the basis of their reported alcohol consumption (QFFQ), %CDT and GGT values. Additionally, subjects were divided into self-reported drinkers and non-drinkers. Men and women were analysed separately. Results: The two alcohol biomarkers %CDT and GGT had different associations with CVD risk factors in this population. The risk of CVD decreased with increasing %CDT level, in that high-density lipoprotein cholesterol (HDL-C) increased significantly with increasing %CDT concentrations for both men and women. There was no significant increase in blood pressure, triglycerides and total cholesterol with increasing %CDT concentrations, except for women, where blood pressure increased significantly with %CDT. Blood pressure, triglycerides and total cholesterol increased significantly with increasing GGT concentrations for both men and women. GGT was also positively associated with HDL-C for both men and women. Self-reported drinkers had a significantly higher HDL-C, blood pressure, %CDT, GGT and lower body mass index (BMI) values than self-reported non-drinkers for both men and women. No significant differences between self-reported drinkers and non-drinkers were seen for triglycerides and total serum cholesterol (even after adjusting for BMI and smoking) for both men and women. Conclusions: In this population-based study, increased alcohol consumption was associated with higher HDL-C levels but also with increased blood pressure values, indicating that the cardioprotective effect of alcohol possibly may disappear because the increase in blood pressure offsets the benefits of the increase in HDL-C.