Alcohol intake and blood pressure: the importance of time elapsed since last drink.

BACKGROUND: A positive association of chronic exposure to alcoholic beverages with blood pressure and the prevalence of hypertension has been described in epidemiological surveys, but the influence of time elapsed since last ingestion in this setting was not demonstrated.
DESIGN: A cross-sectional, population-based survey.
METHODS: In total 1089 adults from Porto Alegre, randomly selected from a population-based, multi-stage probability sample, were interviewed at home. The average daily alcohol intake of each subject was calculated taking into account the concentration of ethanol in the beverages (distilled or fermented beverages), and the time elapsed between the last ingestion of ethanol and the moment of blood pressure determination. Standardized sitting blood pressure and anthropometric parameters were collected. The magnitude and shape of the associations were analyzed considering blood pressure as a continuous variable and the prevalence of arbitrarily defined hypertension. Simple and multiple linear regression models, including models to identify nonlinear associations, with quadratic and cubic terms of the amount of alcohol consumed, were employed. Blood pressure means were compared by analysis of variance and analysis of covariance. The association between hypertension and exposure to ethanol was analyzed through logistic regression models, controlling for various potential confounders.
RESULTS: Positive nonlinear associations of the amount of alcohol consumed with blood pressure and the prevalence of hypertension (> or = 160/95 mmHg) were found, independent of age, years of education, smoking, and use of oral contraceptive and antihypertensive drugs. The consumption of 30 g/day ethanol was associated with increases of 1.5 and 2.3 mmHg in diastolic and systolic blood pressures, respectively, for men, and 2.1 and 3.2 mmHg, respectively, for women. The prevalence of hypertension was higher among those ingesting more than 30 g/day (odds ratio = 2.9, P < 0.01). The time elapsed between the last ingestion and blood pressure measurement was independently associated with the prevalence of hypertension. Men with last consumption of alcohol 13-23 h prior to measurement had odds of being hypertensive 2.6 (confidence interval 1.3-5.0) greater than did subjects who had consumed alcoholic beverages 24 h and more before the blood pressure determination. For men, systolic and diastolic blood pressures were lower during the first 3 h after ingestion and increased afterward. Frequency of consumption and type of beverage consumed were not independently associated with level of blood pressure.
CONCLUSION: A time-dependent association between alcohol consumption and effects on blood pressure, demonstrated in experimental studies, was found for free-living individuals selected at random.