Association Between Daily Alcohol Intake and Risk of All-Cause Mortality

Abstract

The proposition that low-dose alcohol use protects against all-cause mortality in general populations continues to be controversial.¹ Observational studies tend to show that people classified as “moderate drinkers” have longer life expectancy and are less likely to die from heart disease than those classified as abstainers.² Systematic reviews and meta-analyses of this literature³ confirm J-shaped risk curves (protective associations at low doses with increasing risk at higher doses). However, mounting evidence suggests these associations might be due to systematic biases that affect many studies. For example, light and moderate drinkers are systematically healthier than current abstainers on a range of health indicators unlikely to be associated with alcohol use eg, dental hygiene, exercise routines, diet, weight, income⁴; lifetime abstainers may be systematically biased toward poorer health⁵; studies fail to control for biases in the abstainer reference group, in particular failing to remove “sick quitters” or former drinkers, many of whom cut down or stop for health reasons²; and most studies have nonrepresentative samples leading to an overrepresentation of older White men. Adjustment of cohort samples to make them more representative has been shown to eliminate apparent protective associations.⁶ Mendelian randomization studies that control for the confounding effects of sociodemographic and environmental factors find no evidence of cardioprotection.⁷