Alcohol intake, hypertension development and mortality in black South Africans.

BACKGROUND: Excessive alcohol intake is a risk factor for cardiovascular disease (CVD) and predicts cardiovascular and all-cause mortality. We determined which alcohol marker (self-reported alcohol intake, gamma-glutamyltransferase (GGT) or percentage carbohydrate deficient transferrin (%CDT)) relates best with mortality and predicts hypertension development over five years in black South Africans. DESIGN: This was a longitudinal study as part of the PURE (Prospective Urban and Rural Epidemiology) study in the North West Province, South Africa. METHOD: We included 2010 participants and followed 1471 participants. Over five years, 230 deaths occurred, of which 66 were cardiovascular-related. At enrolment, participants completed questionnaires on alcohol intake (yes, for former and current use; no, for alcohol never used). We measured blood pressure, collected blood samples and measured GGT and %CDT. RESULTS: When comparing hazard ratios (HRs) of self-report, GGT and %CDT, we found that only GGT predicted cardiovascular (HR = 2.76 (1.49-5.12)) and all-cause mortality (HR = 2.47 (1.75-3.47)) and hypertension development ((HR = 1.31 (1.06-1.62)). Participants self-reporting yes for alcohol intake had a 30% increased risk of developing hypertension (HR = 1.30 (1.07-1.60)) but not an increased risk for mortality. When adding both GGT and self-report in the prediction model for hypertension, only self-reporting of alcohol was significant (HR = 1.24 (1.01-1.53)). The alcohol marker, %CDT, did not show any significant association with mortality or hypertension development. CONCLUSION: GGT independently predicted cardiovascular and all-cause mortality, as well as hypertension development in black South Africans. Despite non-specificity to excessive alcohol consumption, GGT may be a useful general marker for hypertension development and mortality, also due to its significant association with self-reported alcohol intake.

Self-reported alcohol intake is a better estimate of 5-year change in blood pressure than biochemical markers in low resource settings: the PURE study.

BACKGROUND: Despite criticism of self-reported alcohol intake, it is a valuable tool to screen for alcohol abuse as a risk factor for cardiovascular disease. We aimed to compare various self-reported estimates of alcohol use with γ-glutamyltransferase (GGT) and percentage carbohydrate deficient transferrin (%CDT) considering their relationship with blood pressure changes (%BP) over a 5-year period in black South Africans. METHOD: We recruited 1994 participants and collected 5-year followed up data (N = 1246). Participants completed questionnaires on alcohol intake indicating their former and current alcohol use ('yes' response and 'no' if alcohol was never used). We assessed alcohol intake (in g) using a quantified food frequency questionnaire. We collected blood samples and measured GGT and %CDT. Brachial BP (bBP) was measured at baseline and follow-up and central BP (cBP) at follow-up only. RESULTS: Self-reported alcohol intake was significantly associated with the 5-year change in bBP before and after adjusting for confounders (%bSBP: R(2) = 0.263, ß = 0.06, P = 0.023; %bDBP: R(2) = 0.326, ß = 0.08 P = 0.005), as well as cSBP (R (2)= 0.286, ß = 0.09, P = 0.010) and central pulse pressure (R(2) = 0.254, ß = 0.06, P = 0.020). GGT and %CDT correlated well with self-reported alcohol intake (r = 0.44; P = 0.001; r = 0.34 P = 0.001), but did not associate significantly with %bBP or cBP at follow-up. CONCLUSION: Self-reported alcohol use was strongly associated with a 5-year increase in BP in Africans with a low socio-economic status. This was not found for biochemical measures, GGT and %CDT. Self-reported alcohol intake could be an important measure to implement in primary healthcare settings in middle to low income countries, where honest reporting is expected.