Many people believe that having a glass of wine with dinner – or moderately drinking any kind of alcohol – will protect them from heart disease. But a hard look at the evidence finds little support for that.
Over the years, studies have found that adults who drink moderately have lower heart disease rates than non-drinkers. That has spurred the widespread belief that alcohol, in moderation, does a heart good.
But the new analysis, of 45 previous cohort studies, reveals the flaws in that assumption: A central issue is that "non-drinkers" may, in fact, be former drinkers who quit or cut down for health reasons. Furthermore, seniors who are healthy may be more likely to keep enjoying that glass of wine with dinner.
"We know that people generally cut down on drinking as they age, especially if they have health problems," said researcher Dr Tim Stockwell, director of the Centre for Addictions Research at the University of Victoria, in British Columbia, Canada.
"People who continue to be moderate drinkers later in life are healthier," Stockwell said. "They're not sick, or taking medications that can interact with alcohol." And in studies, that can lead to a misleading association between moderate drinking and better health.
In their analysis, Stockwell's team found that overall, "current" moderate drinkers (up to two drinks per day) did, in fact, have a lower rate of heart disease death than non-drinkers. However, that was not the case in studies that looked at people's drinking habits at relatively young ages – age 55 or earlier – and followed them to their older years when heart disease might strike. Similarly, studies that rigorously accounted for people's heart health at baseline indicated no benefits from moderate drinking.
According to Stockwell, it all suggests that "abstainers" tend to be less healthy than moderate drinkers – but not because they never drank. Instead, their health may influence their drinking choices. That is, they may not drink because their health is poor.
"We can't 'prove' it one way or the other," Stockwell noted. "But we can say there are grounds for a healthy skepticism around the idea that moderate drinking is good for you."
A second study in the same issue supports that.
That research followed more than 9,100 UK adults from the age of 23 to 55. Overall, researchers found that people's drinking habits evolved over time – and few were actually lifelong "abstainers." Nearly all people who were non-drinkers at age 55 had given up alcohol.
What's more, non-drinkers – even those in their 20s – tended to be in poorer physical and mental health compared with those who drank moderately and did not smoke. They were also, on average, less educated, and education is an important factor in lifetime health.
However, no one is saying that people who enjoy alcohol in moderation should stop. "The risks of low-level drinking are small," Stockwell said. But, he added, people should not drink solely because they believe it wards off disease. "The notion that one or two drinks a day is doing us good may just be wishful thinking," Stockwell said.
Abstract
Objective: Previous meta-analyses estimate that low-volume alcohol consumption protects against coronary heart disease (CHD). Potential errors in studies include systematic misclassification of drinkers as abstainers, inadequate measurement, and selection bias across the life course.
Method: Prospective studies of alcohol consumption and CHD mortality were identified in scholarly databases and reference lists. Studies were coded for potential abstainer biases and other study characteristics. The alcohol–CHD risk relationship was estimated in mixed models with controls for potential biases. Stratified analyses were performed based on variables identified as potential effect modifiers.
Results: Fully adjusted meta-analysis of all 45 studies found significantly reduced CHD mortality for current low-volume drinkers (relative risk [RR] = 0.80, 95% CI [0.69, 0.93]) and all current drinkers (RR = 0.88, 95% CI [0.78, 0.99]). There was evidence of effect modification by cohort age, gender, ethnicity, and heart health at baseline.
In stratified analyses, low-volume consumption was not significantly protective for cohorts ages 55 years or younger at baseline (RR = 0.95, 95% CI [0.75, 1.21]), for studies controlling for heart health (RR = 0.87, 95% CI [0.71, 1.06]), or for higher quality studies (RR = 0.86, 95% CI [0.68, 1.09]). In studies in which the mean age was 55 years or younger at baseline, there were significantly increased RRs for both former (RR = 1.45, 95% CI [1.08, 1.95]) and occasional drinkers (RR = 1.44, 95% CI [1.09, 1.89]) compared with abstainers.
Conclusions: Pooled analysis of all identified studies suggested an association between alcohol use and reduced CHD risk. However, this association was not observed in studies of those age 55 years or younger at baseline, in higher quality studies, or in studies that controlled for heart health. The appearance of cardio-protection among older people may reflect systematic selection biases that accumulate over the life course.
Authors
Jinhui Zhao, Tim Stockwell, Audra Roemer, Timothy Naimi, Tanya Chikritzhs
[link url="https://www.sciencedaily.com/releases/2017/05/170522080805.htm"]Journal of Studies of Alcohol and Drugs material[/link]
[link url="http://www.jsad.com/doi/10.15288/jsad.2017.78.375"]Journal of Studies of Alcohol and Drugs abstract[/link]