The benefits of alcohol may not be as large or as broad as previous estimates, according to a new analysis. In fact, alcohol-related reductions in all-cause mortality may be limited to younger men, aged 50 to 64 years, who drink 15 to 20 units per week, and women aged 65 years or older.
Other, previously documented beneficial associations between low-intensity alcohol consumption and all-cause mortality may be the result of inappropriate selection of a referent group as well as weak adjustment for cofounders, according to the authors.
Craig S. Knott, from the University College London, United Kingdom, and colleagues published the results of their population-based study online February 10 in the BMJ. The authors note that their methods differ from previous studies, in that they adjusted for a more comprehensive list of confounders and restricted their referent group to never-drinkers. Prior studies typically included both never-drinkers and former-drinkers in the referent group. “The case for omitting former drinkers from an abstention category is supported by their higher hazards compared with never drinkers,” the authors explain.
The investigators pooled data from 10 large population-based surveys that were representative of the noninstitutionalized English population from 1998 to 2008. They stratified their by age group (50 – 64 years and ≥65 years) and sex and included deaths through March 31, 2011.
The investigators used two measures of alcohol consumption: average weekly consumption and use on the heaviest drinking day in the week before interview. The estimates depended on self-reported data and were thus limited by participant recall.
Adjusted Analyses Mitigate Benefit
Initial models, adjusted only for age, show reduced mortality risk was associated with both measures of alcohol consumption for all age and sex groups except for women aged 50 to 64 years.
However, in fully adjusted models, the beneficial effects were no longer significant, except among men aged 50 to 65 years and women aged 65 years or older. In men, the protection against all-cause mortality was limited to men who consumed 15.1 to 20.0 units/average week (hazard ratio [HR], 0.49; 95% confidence interval [CI], 0.26 – 0.91) or 0.1 to 1.5 units on the heaviest day (HR, 0.43; 95% CI, 0.21 – 0.87).
For older women (≥65 years), protection against all-cause mortality was associated with a broader drinking range (≤10 units/average week), but the protective effect was lower than for men (HR, 0.58; 95% CI, 0.39 – 0.87).
In an accompanying editorial, Mike Daube, AO, from Curtin University, Perth, Australia, emphasizes that industry lobbying and promotion have confounded the public health discussion on alcohol consumption.
“Firstly, in health as elsewhere, if something looks too good to be true, it should be treated with great caution. Secondly, health professionals should discourage suggestions that even low level alcohol use protects against cardiovascular disease and brings mortality benefits. Thirdly, health advice should come from health authorities, not from the alcohol industry, and, finally, the alcohol industry and its organisations should remove misleading references to health benefits from their information material,” writes Daube.
Never Drinkers as Referent Group
Knott and colleagues explain that most of the previously demonstrated protective associations between alcohol consumption and health could be explained by selection bias across age–sex strata. They further suggest that previous studies may have pooled never-drinkers with a less-healthy group of former drinkers who are at a higher risk for mortality. Therefore, they wanted to adjust for this by excluding former drinkers from referent categories.
“Through improved referent group selection, the analyses undertaken for this study may have better isolated the true effect of alcohol consumption on mortality,” they write. In addition, their age-stratified analysis suggests risk profiles may differ by age group. The investigators suggest that future prospective studies should further stratify their dose–response analyses by age.
The authors and Daube have disclosed no relevant financial relationships.
BMJ. Published online February 10, 2015. Article full text, Editorial full text