In a follow-up analysis of almost 50,000 young women, aged 30-49 at baseline, in the Swedish Women’s Lifestyle and Health cohort, the authors used self-reported information on alcohol consumption on two occasions, 12 years apart, to estimate the effects of alcohol on overall and cause-specific mortality. There were 2,100 deaths during follow up. Effects of alcohol on the two occasions, and changes between the two assessments among 33,000 women with available data, were related to mortality, as assessed from virtually complete national records.
Using “light” drinkers (0.1 – 1.49 grams of alcohol/day) as the referent group, the authors report an inverse association between greater amounts of alcohol consumption and mortality from cardiovascular disease. They report increased risk of cardiovascular and total mortality for abstainers. Despite the large number of total subjects, the authors report results separately for relatively narrow ranges of alcohol intake (none, 0.1-1.49, 1.5-4.9, 5-9.9, 10-14.9, 15+ g/day), which makes the numbers of subjects in many groups quite small. Given that the total mortality risks for most groups of drinkers were similar, it would have been interesting to see the effects of alcohol consumption (versus no consumption) using a broader definition of “moderate” drinking.
Forum members in general thought that this was a well-done study, using an excellent source of national records available in Sweden for determining mortality. They had concerns that the under-reporting of alcohol intake was not addressed; there is a high probability that some of the supposedly “light” drinkers may have actually consumed more alcohol, which would tend to decrease any differences between the referent group and the next groups of drinkers. This could help explain why, despite the strikingly lower risk ratios for cardiovascular disease for all drinkers when compared with the referent group, the inverse relation of alcohol was not statistically significant for any single group considered alone.
The Forum was also concerned that while the investigators had data on binge drinking and whether or not alcohol was usually consumed with meals, they chose not to include these data in their analyses. Given that drinking pattern plays a large role in determining favorable or unfavorable health effects of alcohol, the inclusion of such information may have better delineated the true effects of alcohol. Also, the authors “chose not to separately study the effects of different alcohol beverages;” reporting effects separately for beer, wine, and spirits could have provided key data on the effects of alcohol consumption.
The attempt of the authors to judge the effects of changes in alcohol intake during the study is laudable. Importantly, data on the reason that a woman may decide to increase or decrease her intake is not known; if due to the development of a serious disease, it may be the disease and not the change in alcohol intake that relates to subsequent mortality. However, given the inherent problems in assessing change, the results of this study are consistent with other studies that have suggested an increase in mortality risk for moderate drinkers who stop their alcohol consumption.
Reference: Licaj I, Sandin S, Skeie G, Adami H-O, Roswall N, Weiderpass E. Alcohol consumption over time and mortality in the Swedish Women’s Lifestyle and Health cohort. BMJ Open 2016;6:e012862. doi:10.1136/ bmjopen-2016-012862