Friday, March 25, 2016
A very large review out recently has experts proclaiming that we had it all wrong in believing that moderate drinking was a good thing. As I so often do, I cast a dissenting vote on this one, and offer an alternative (and possible more accurate) interpretation.
This latest study, from the University of Victoria in Canada, is impressive in scope and has been widely reported. In it, Tim Stockwell, study author and the director of the Center for Addictions Research of British Columbia, questions the long-established J-shaped curve which demonstrates that moderate drinkers are healthier and outlive nondrinkers and heavy drinkers. He cites what is termed the “abstainer bias,” meaning that people who choose to abstain from alcohol are different than people who quit drinking because of health reasons. Another term for this is the “sick quitter” hypothesis. The result of lumping sick quitters with never drinkers together is a skew toward poor health in the nondrinker group, resulting in a greater apparent difference between them and moderate drinkers. The study is a review of other published studies, called a meta-analysis, and it attempted to resolve the question by separating those that differentiate between never drinkers and sick quitters. In so doing, they found that the net benefit of moderate drinking vanishes.
Or not. Meta-analysis can be a tool for teasing out subtle statistical trends, but it can also magnify existing biases. A better way to ask the question is “What happens to lifelong abstainers who start drinking, and what happens to healthy moderate drinkers who quit?” This was addressed neatly in a 2008 study from Australia, which prospectively followed more than 13,000 subjects for 12 years. The study substantiated the J-shaped curve, with moderate drinkers enjoying a higher overall health score than nondrinkers, as expected. More importantly, when moderate drinkers changed their habits – either reducing or increasing their consumption – their health scores deteriorated. They further found that the health of recent abstainers and intermittent drinkers was the same as longer-term abstainers. This held true even after adjusting for chronic health conditions. In other words, no evidence for abstainer bias was found.
Perhaps a bias not considered by the authors of the UVC study was the fact that the project was done under the auspices of an addiction center, presumably disinclined to promote healthy drinking. A commentary that accompanied the paper came from the Alcohol Research Group in Emeryville, California, whose mission “seeks to reduce alcohol-related harms,” lauded the findings. They said it could help fight back against “renewed calls from certain medical commentators to prescribe moderate drinking.” I count myself one of those certain medical commentators.