Alcohol and heart health: Consistency may be key

The latest study to peer at the relationship between heart health and alcohol concludes that shifting drinking patterns across the years might increase the risk of cardiovascular disease.

Alcohol has been addling minds since it was first brewed millennia ago.

Consumed in virtually every country on earth, understanding its health implications is important.

Already, scientists have tied plenty of health hazards to alcohol. Among other conditions, it increases the risk of certain cancers, stroke, and liver disease.

Heavy drinking has conclusively been shown to harm health, but there is still discussion surrounding the fine print.

For instance, although light drinking has been shown to increase cancer risk, there is also evidence that light drinking could protect the heart.

A recent study found that people who drank one or fewer drinks per day had lower cardiovascular risk than people who drank more, as well as people who abstained completely. Could a small amount of alcohol be heart protective?

However, the increased cardiovascular risk seen in people who do not drink at all may not be what it seems. Some have made the point that individuals who do not drink now might still have been drinkers in the past.

In other words, someone who hasn't touched a drop for months may have still been a heavy drinker for many years in the past.

Alcohol and the heart revisited

The latest study, which is published in the journal BMC Medicine, set out to clear up this query by comparing rates of coronary heart disease (CHD) in individuals who have never drunk and those who used to drink but quit.

As corresponding author Dr. Dara O'Neill, who works at University College London in the United Kingdom, says, "This study uses long-term data to distinguish between persistent non-drinkers and former drinkers, allowing us to test the established theory that only the latter have an elevated risk of CHD."

To investigate whether the theory held true, they examined data from 35,132 people taken from six earlier studies in the U.K. and France. The data included self-reported weekly alcohol intake across a period of 10 years. Of the 35,132 people, 1,718 (4.9 percent) developed CHD. In 325 of the cases (0.9 percent), the person died.

Did persistent non-drinkers have a lower cardiovascular risk than former drinkers, as hypothesized? Dr. O'Neill says, "We did not find this to be the case, but we did observe a sex-related difference. Amongst consistent non-drinkers, women showed higher risk of developing CHD compared to consistently moderate drinkers, but their male counterparts did not."

CHD incidence was highest for former drinkers (6.1 percent had a CHD event), while incidence was lowest in consistently heavy drinkers (3.8 percent experienced a CHD event).

However, the scientists make it clear that because there were so few people who drink heavily in the dataset, the apparent reduction in risk should not be taken as fact.

As Dr. O'Neill points out, "Given that heavy drinkers are known to be undersampled in population-level surveys, interpretation of the absence of effect amongst heavy drinkers in the current study should be done very cautiously, particularly in light of the known wider health impact of heavy alcohol intake levels."

They showed that individuals who drank sensibly and in line with U.K. guidelines over a 10-year period had a lower risk than those who never drank, those who inconsistently drank in moderation, and those who had stopped drinking.

Consistency and fluctuation

According to the authors, these findings suggest that fluctuations in drinking patterns over time are associated with an increase in CHD risk. It is probable that changes in drinking patterns mirror life events, such as long periods of ill health or other life stresses, including divorce, bereavement, or unemployment.

This complex interaction makes studies such as this difficult to draw meaning from. We all have long, complicated lives, wherein a myriad of influences increase or decrease health risks. To investigate these relationships further, the researchers split the data into age groups.

"When we split the sample by age," explains Dr. O'Neill, "we found that the elevated risk of incident CHD amongst inconsistently moderate drinkers was observed in participants aged over 55, but not those aged below," adding:

"It may be that the older group experienced lifestyle changes, such as retirement, which are known to co-occur with increases in alcohol intake and that these could have played a role in the differing risk."

As with any study that looks at alcohol intake and health, there are unavoidable gaps and plenty of room for future improvements. For instance, heavy drinkers who had fallen ill early on in the study may have dropped out, skewing the data.

Also, as ever, this is an observational study, meaning that cause and effect can not be proven. In the long line of studies investigating long-term alcohol intake and heart health, this study adds another slice of information but still leaves plenty of questions unanswered.

Thanks to humanity's fascination with alcohol, studies unpicking its potential benefits and pitfalls are sure to continue.