Alcohol intake, hypertension development and mortality in black South Africans

Abstract

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.

Keywords: Gamma-glutamyltransferase; cardiovascular disease; hypertension; morbidity; percentage carbohydrate deficient transferrin; self-reported alcohol intake; sub-Saharan Africa.