For the regular boozer it is a source of great comfort: the fat pile of studies that say a daily tipple is better for a longer life than avoiding alcohol completely.
But a new analysis challenges the thinking and blames the rosy message on flawed research that compares drinkers with people who are sick and sober.
Scientists in Canada delved into 107 published studies on people's drinking habits and how long they lived. In most cases, they found that drinkers were compared with people who abstained or consumed very little alcohol, without taking into account that some had cut down or quit through ill health.
The finding means that amid the abstainers and occasional drinkers are a significant number of sick people, bringing the group's average health down, and making light to moderate drinkers look better off in comparison.
"It's been a propaganda coup for the alcohol industry to propose that moderate use of their product lengthens people's lives," said Dr Tim Stockwell, first author on the study and a scientist at the Canadian Institute for Substance Use Research at the University of Victoria.
"The idea has impacted national drinking guidelines, estimates of alcohol's burden of disease worldwide and has been an impediment to effective policymaking on alcohol and public health," he added. Details are published in the Journal of Studies on Alcohol and Drugs.
Many studies on the health impact of alcohol show a J-curve effect, where death rates are lowest among those who drink a little. When the Canadian team combined the data from the studies in their analysis, it suggested that light to moderate drinkers – those having between one drink a week and two a day – had a 14% lower risk of dying over the study period compared with abstainers.
Article:
Moderate drinking not better for health than abstaining, analysis suggests
Scientists say flaws in previous research mean health benefits from alcohol were exaggerated
www.theguardian.com
Study:
Why Do Only Some Cohort Studies Find Health Benefits From Low-Volume Alcohol Use? A Systematic Review and Meta-Analysis of Study Characteristics That May Bias Mortality Risk Estimates - PubMed
Studies with lifetime selection biases may create misleading positive health associations. These biases pervade the field of alcohol epidemiology and can confuse communications about health risks. Future research should investigate whether smoking status mediates, moderates, or confounds...
pubmed.ncbi.nlm.nih.gov
Abstract:
Objective: Assumptions about alcohol's health benefits profoundly influence global disease burden estimates and drinking guidelines. Using theory and evidence, we identify and test study characteristics that may bias estimates of all-cause mortality risk associated with low-volume drinking.
Method:
We identified 107 longitudinal studies by systematic review with 724 estimates of the association between alcohol consumption and all-cause mortality for 4,838,825 participants with 425,564 recorded deaths. "Higher-quality" studies had a mean cohort age of 55 years or younger, followed up beyond 55 years, and excluded former and occasional drinkers from abstainer reference groups. "Low-volume" alcohol use was defined as between one drink per week (>1.30 g ethanol/day) and two drinks per day (<25 g ethanol/ day). Mixed linear regression was used to model relative risks (RRs) of mortality for subgroups of higher- versus lower-quality studies.
Results:
As predicted, studies with younger cohorts and separating former and occasional drinkers from abstainers estimated similar mortality risk for low-volume drinkers (RR = 0.98, 95% CI [0.87, 1.11]) as abstainers. Studies not meeting these quality criteria estimated significantly lower risk for low-volume drinkers (RR = 0.84, [0.79, 0.89]). In exploratory analyses, studies controlling for smoking and/or socioeconomic status had significantly reduced mortality risks for low-volume drinkers. However, mean RR estimates for low-volume drinkers in nonsmoking cohorts were above 1.0 (RR = 1.16, [0.91, 1.41]).
Conclusions:
Studies with lifetime selection biases may create misleading positive health associations. These biases pervade the field of alcohol epidemiology and can confuse communications about health risks. Future research should investigate whether smoking status mediates, moderates, or confounds alcohol-mortality risk relationships.
