Message About Alcohol Use and CV Risk Should Be 'More Nuanced' Than It Now Is

Liam Davenport

April 03, 2017

LONDON, UK — Moderate intake of alcoholic drinks is associated with a lower risk of only some cardiovascular diseases, not all, compared with either abstinence or heavy drinking, suggests research conducted in the UK[1]. Its investigators concluded that public-health messages and discussions with patients about alcohol and CV risk be "more nuanced" than what is currently typical.

Their study using the electronic health records of almost 2 million individuals showed that the risk of incident cardiovascular disease and CV mortality was increased among abstainers vs those who were moderate drinkers for six of the 12 cardiovascular conditions in the analysis. A similar pattern was seen when comparing heavy with moderate drinking.

The findings complement recent studies indicating that the relationship between alcohol and cardiovascular risk is more complex than often  thought. For example, a meta-analysis of 23 studies suggested that moderate alcohol consumption is associated with a greater risk of having an MI or stroke within hours, but a lower risk of these outcomes within a day or a week.

It remains "sound advice" to tell people who choose to drink to "do so in moderation," Dr Steven Bell (University of Cambridge, UK) told heartwire from Medscape.

"I would be very reluctant to encourage doctors to recommend nondrinking patients to take up drinking as a means of lowering their risk of developing a cardiovascular disease, as there are safer and more effective means of doing so—for example, through increasing levels of physical activity, following a healthy diet, or quitting smoking," said Bell, who is lead author on the current analysis, which was published March 22, 2017 in the BMJ. "This is a viewpoint endorsed also by the likes of the American Heart Association."

Bell noted that, while a great deal of the focus on his research in the media has been on non- and moderate drinkers, "it's also worth bearing in mind that heavy drinkers had a greater risk of developing seven out of the 12 cardiovascular diseases we looked at."

He said: "Suggesting that patients who present with high alcohol intake should be urged to reduce their drinking would also seem like sensible advice, not only in terms of lowering their risk of cardiovascular diseases but a variety of other chronic and acute conditions."

In an accompanying editorial[2], Dr Kenneth Mukamal (Harvard Medical School, Boston, MA) and Dr Mariana Lazo (Johns Hopkins School of Public Health and School of Medicine, Baltimore, MD) say that studies combining electronic health records with IT advances "represent a promising convergence between medicine, public health, and research."

Nevertheless, they point out that the current study doesn't offer "a materially new view" of the association between moderate alcohol consumption and reduced cardiovascular disease risk, as "four decades of epidemiological studies have largely found the same." It does, however, "set the stage for ever larger and more sophisticated studies that will attempt to harness the flood of big data into a stream of useful, reliable, and unbiased findings that can inform public health, clinical care, and the direction of future research."

To examine the association between alcohol consumption and specific cardiovascular diseases, the researchers studied the electronic health records of 1,937,360 individuals as part of the Clinical Research Using Linked Bespoke Studies and Electronic Health Records (CALIBER) project.

The participants, of whom 51% were female, were aged at least 30 years and were free from cardiovascular disease at baseline. Their records covered primary care, hospital admissions, and mortality for 1997–2010, with a median follow-up of 6 years, or 11,637,926 person-years.

The researchers focused on 12 common manifestations of cardiovascular disease, including chronic stable angina, unstable angina, acute MI, unheralded coronary heart disease death, and heart failure.

Using records of self-reported alcohol consumption for the 5 years before study entry, the team were able to classify 14.3% of the participants as nondrinkers, while 3.7% were former drinkers, 11.9% were occasional drinkers, 61.7% were moderate drinkers, and 8.4% were heavy drinkers. Alcohol status was missing for 16.1% of the cohort.

During follow-up, 114,859 individuals received a cardiovascular diagnosis.

As has been seen in previous studies, there was a J-shaped curve for associations between alcohol consumption for all and fatal cardiovascular disease, as well as for all-cause mortality. Specifically, nondrinking and heavy drinking were associated with an increased risk of fatal and nonfatal cardiovascular disease compared with moderate drinking, at hazard ratios (HRs) of 1.23 (95% CI 1.19–1.27) and 1.14 (95% CI 1.10–1.19), respectively, while the respective HRs for all-cause mortality were 1.24 (95% CI 1.20–1.28) and 1.34 (95% CI 1.31–1.38).

Looking at specific phenotypes of cardiovascular disease, the team found that, compared with moderate drinking, nondrinking was associated with a significantly increased risk for six of the 12 conditions, namely:

  • Unstable angina (HR 1.33, 95% CI 1.21–1.45).

  • MI (HR 1.32, 95% CI 1.24–1.41).

  • Unheralded CHD death (HR 1.56, 95% CI 1.38–1.76).

  • Heart failure (HR 1.24, 95% CI 1.11–1.38).

  • Peripheral artery disease (HR 1.22, 95% CI 1.131.32).

  • Abdominal aortic aneurysm (HR 1.32, 1.17–1.49).

Heavy drinking was associated with an increased risk vs moderate drinking of:

It's possible that it may not be alcohol per se that is causing the effects, but rather other, unknown factors associated with its consumption, according to Bell. "This is a perennial concern with any observational study," he said. "We cannot rule out the possibility that other factors associated with nondrinking or heavy drinking, whether these be physical or social, explain why they have a greater risk of developing several different cardiovascular diseases compared with moderate drinkers, as opposed to the lack of, or increased level of, drinking itself.

"Conversely, the complex picture we see may reassure some people that the effects we observe are genuine, as one might argue that if alternative factors were the [sole explanation], they might have a similar influence across disease end points."

Following on from the current findings, "a logical advancement of this work would be to more thoroughly investigate the shape of the dose–response association among drinkers, to determine at approximately what level of alcohol intake an individual's risk begins to increase."

Bell added that more work is also needed to understand how, exactly, alcohol consumption affects cardiovascular disease risk, as the evidence base for the majority of proposed mechanisms is lacking. "For example, moderate drinking increasing levels of HDL cholesterol is often cited as a reason as moderate drinkers' lower risk of CVD than nondrinkers; however, drug therapies aimed at raising HDL levels have not shown clinical benefits."

However, a "definitive answer" as to whether moderate drinking is truly protective against cardiovascular disease "will not be reached in the absence of evidence from a long-term randomized trial."

This work was supported by the National Institute for Health Research, Wellcome Trust, the Medical Research Council prognosis research strategy (PROGRESS) Partnership, and awards to establish the Farr Institute of Health Informatics Research at UCLPartners, from the Medical Research Council, Arthritis Research UK, British Heart Foundation, Cancer Research UK, Chief Scientist Office, Economic and Social Research Council, Engineering and Physical Sciences Research Council, National Institute for Health Research, National Institute for Social Care and Health Research, and Wellcome Trust. The authors report no relevant financial relationships. Lazo previously held a research grant from ABMRF/The Foundation for Alcohol Research, which is funded in part by industry, for a project on alcohol and liver disease.

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