Association of Alcohol Consumption with Specific Biomarkers: A Cross-sectional Study in South Africa.

Alcohol consumption plays an important role in the health transition associated with urbanization in developing countries. Thus, reliable tools for assessing alcohol intake levels are necessary. We compared two biological markers of alcohol consumption and self-reported alcohol intakes in participants from urban and rural South African communities. This cross-sectional epidemiological survey was part of the North West Province, South African leg of the 12-year International Prospective Urban and Rural Epidemiology (PURE) study which investigates the health transition in urban and rural 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. Alcohol consumption was assessed through self-reports (24-hour recalls and quantitative food frequency questionnaire) and by two biological markers: percentage carbohydrate-deficient transferrin (%CDT) and gamma-glutamyl transferase (GGT). Of the 716 men and 1,192 women volunteers, 64% and 33% respectively reported regular alcohol consumption. Reported mean habitual intakes of drinker men and women were 29.9 (±30.0) and 23.3 (±29.1) g of pure alcohol per day. Reported habitual intake of the whole group correlated positively and significantly with both %CDT (R=0.32; p≤0.01) and GGT (R=0.43; p≤0.01). The correlation between the two biomarkers was low (0.211; p≤0.01). GGT and %CDT values should be interpreted with care in Africans as self-reported non-drinker men and women had elevated levels of GGT (19% and 26%) and %CDT (48% and 38%). A need exists for a more specific biological marker for alcohol consumption in black Africans.

Lack of Association of Glycated Haemoglobin with Blood Pressure and Subclinical Atherosclerosis in Black South Africans: a Five-Year Prospective Study

Objectives: Hypertension and diabetes are common in rapidly urbanising sub-Saharan African communities. However; lack of longitudinal data in these regions prevents adequate analysis of the link between measures of glycaemia and cardiovascular disease. Therefore; we examined the relationships of fasting glucose and glycated haemoglobin (HbA1c) with brachial and central blood pressure (BP); and measures of vascular structure and function after five years in black South Africans.Setting and subjects: Nine hundred and twenty-eight participants were included as part of the Prospective Urban Rural Epidemiological (PURE) study in the North West Province.Outcome measures: Fasting glucose; HbA1c and brachial BP at two time points were determined. Central BP; augmentation index (AI) and carotid intima-media thickness (CIMT) were taken at follow-up. Results: Fasting glucose [4.78 (3.50; 6.30) vs. 5 mmol/l (3.96; 6.42)]; HbA1c [5.6 (4.9; 6.3) vs. 5.9 (5.2; 6.9) and (37 vs. 41 mmol/mol)]; and BP (134/88.1 vs. 138/89.5 mmHg) increased significantly over five years (p-value 0.05). However; an association was absent between BP; AI or CIMT and either baseline or the five-year change in glucose or HbA1c. Multivariate analyses confirmed that neither glucose or HbA1c predicted changes in BP; CIMT or AI; but factors that did associate significantly were age; male gender; rural location; abdominal obesity; alcohol intake; total cholesterol to high-density lipoprotein ratio; C-reactive protein and antihypertensive medication (R2; ranging from 0.24-0.36).Conclusion: Although both BP and measures of glycaemia increased significantly over five years in black South Africans; glucose was not independently associated with BP or measures of large artery structure or function. We suggest that fasting glucose and HbA1c below the threshold of diagnosing diabetes should not be used in isolation to predict cardiovascular risk in African individuals

Sex Differences Independent of Other Psycho-sociodemographic Factors as a Predictor of Body Mass Index in Black South African Adults.

To better understand the sex differences in body mass index (BMI) observed in black South African adults in the Transition and Health during Urbanization of South Africans Study, the present study investigated whether these differences can be explained by the psycho-sociodemographic factors and/or health-related behaviours. A cross-sectional survey was undertaken among 1,842 black South African individuals from 37 study sites that represented five levels of urbanization. The behavioural factors that possibly could have an influence on the outcome of body-weight and that were explored included: diet, smoking, level of education, HIV infection, employment status, level of urbanization, intake of alcohol, physical activity, and neuroticism. The biological factors explored were age and sex. The prevalence of underweight, normal weight, and overweight among men and women was separately determined. The means of the variables were compared by performing Student’s t-test for normally-distributed variables and Mann-Whitney Utest for non-normally-distributed variables. The means for the underweight and overweight groups were tested for significant differences upon comparison with normal-weight individuals stratified separately for sex. The differences in prevalence were tested using chi-square tests (p<0.05). All the variables with a large number of missing values were tested for potential bias. The association between sex and underweight or overweight was tested using the Mantel-Haenszel method of odds ratio (OR) and calculation of 95% confidence interval (CI), with statistical significance set at p<0.05 level. Logistic regression was used for controlling for confounders and for testing for effect modification. Females were more likely to be overweight/ obese (crude OR=5.1; CI 3.8-6.8). The association was attenuated but remained strong and significant even after controlling for the psycho-sociodemographic confounders. In this survey, the risk for overweight/ obesity was strongly related to sex and not to the psycho-sociodemographic external factors investigated. It is, thus, important to understand the molecular roots of sex- and gender-specific variability in distribution of BMI as this is central to the future development of treatment and prevention programmes against overweight/obesity.

Iron status and cardiovascular disease risk in black South African women: the PURE study

Objective: To examine the associations between measures of iron status and cardiovascular disease (CVD) risk factors in South African women.Method: In a cross-sectional study; demographic information and health history were obtained during individual interviews using validated questionnaires in the North West Province; South Africa. Anthropometric indices; iron indices; blood pressure; blood glucose and lipid profiles were measured using standard procedures in 1 262 apparently healthy black South African women aged 35 years or older. Iron status was assessed using serum concentrations of ferritin; transferrin receptor (TfR) and TfR:ferritin ratio.Results: Associations between iron status parameters and CVD risk factors were generally weak (r 0.3; p 0.01) and were not retained when adjustment was made for age; body mass index; smoking; alcohol consumption and C-reactive protein in the analysis. Waist circumference (WC) and waist:hip ratio (WHR) were higher in the fourth quartile of serum ferritin than in the third quartile; and also in the third quartile compared to the second quartile (P 0.05). Based on WC and WHR respectively; 31 and 52of the women had excess abdominal obesity. The mean (95 confidence interval) serum TfR concentration was high; at 9.09 ?g/ml (8.77; 9.44); indicating risk of iron deficiency. The mean (95 confidence interval) concentrations of lipids [total cholesterol 4.78 mmol/l (4.64; 4.93); high-density lipoprotein cholesterol 1.45 mmol/l (1.39; 1.52); low-density lipoprotein cholesterol 1.65 mmol/l (1.53; 1.78); triglyceride 1.12 mmol/l (1.07; 1.18)] were within reference ranges.Conclusion: No significant association was found between iron status parameters and established CVD risk factors. However; excessive abdominal adiposity indicated by high WC and WHR contributes significantly to increased serum ferritin concentration in this population