Moderate But Inconsistent Drinking Associated with High CHD Risk

Becky McCall

August 22, 2018

Moderate alcohol consumption that is 'inconsistent' over time may be linked to an increased incidence of coronary heart disease (CHD), compared to moderate drinking that is 'consistent' which may be cardio-protective, suggests a study that observed drinking habits in the UK and France over 10-years.

The study looked at the potential association between moderate drinking and a lower risk of coronary heart disease by taking into account how drinking behaviours change over time. "Our findings support the theory that low levels of alcohol intake may be linked to a reduced risk of some cardiovascular issues, and show how it's not just the volume we drink but the stability of our drinking levels over time that may play a role in that association," said Dara O'Neill, PhD, from University College London in an interview for Medscape News UK.

The research, which was carried out by University College London and the University of Cambridge, is published in this week's open access journal BMC Medicine.

Results also show that incident CHD risk is significantly higher amongst both non-drinkers and former drinkers compared to drinkers who always adhered to lower-risk alcohol intake guidelines.

Moderate but Inconsistent Drinking

Reflecting on the findings relating to people who drink moderately but inconsistently, O'Neill remarked that, "this is often due to occasional periods of heavy drinking which may have harmful effects on health and negate any potential cardio-protective effect of moderate drinking." Typical reasons for inconsistent moderate drinking might include, for example, periods of ill health that sometimes lead to lifestyle changes including greater alcohol consumption, or life events such as retirement, known to be associated with increased alcohol intake, particularly among existing drinkers, note the authors. 

Exercising caution in interpreting the results, Dr Naveed Sattar, professor of metabolic medicine at the University of Glasgow, placed the findings in the context of other recent research, in particular a study published in The Lancet. This showed that, "…whilst risk for myocardial infarction may well be lower with modest alcohol, risk for other complications of the heart and brain increase with even moderate drinking."

"Indeed, drinking about the recommended levels of around five drinks per week was linked to increased risks of stroke, fatal aneurysm, heart failure and death," he said, adding that, "if you drink, drinking less may help you live longer and lower risk of several vascular complications… but no one should start to drink or drink more to protect their hearts. The totality of evidence does not support alcohol as a measure to improve overall risks."

Six Cohorts, Over 35,000 Sample Size

The study aimed to explore the relationship between alcohol intake patterns over time and actual CHD incidence (fatal and non-fatal) as opposed to biomarkers of cardiovascular functioning that is already known. Self-reported data on weekly alcohol consumption, and CHD outcomes, were drawn from a total of six cohorts (five from the UK; one from France), comprising data collected prospectively over 10 years. A sample of 35,132 (62.1% male) participants were included in the analysis.

In this study, the term 'consistency', related to how stable alcohol intake levels were over time. Three measures of alcohol intake were taken over approximately 10 years to determine whether participants were drinking at broadly the same level across time points, or whether they demonstrated noticeable changes in intake levels.  

Intake was based on the alcohol content in reported drinks including half pints of beer or cider, small glasses of wine, and a single serving of spirits, which were recorded as containing 8g of ethanol in the UK cohorts, and 10g in the French cohort. Moderate drinking was considered to be up to 168g ethanol per week for men, and up to 112g ethanol per week for women.

Inconsistently Moderate, Former and Persistent Non-drinkers Show Greater CHD Risk

Overall, 1,718 (4.9%) out of the 35,132 individuals included in the six cohorts developed CHD over the 10 years of study duration, of which 325 (0.9%) were fatal CHD events.

All comparisons were made to consistently moderate drinkers. Inconsistently moderate drinkers were found to have a significantly greater risk of incident CHD (hazard ratio (HR) 1.18, 95% confidence interval (CI): 1.02 – 1.37). 

Former drinkers also demonstrated an elevated risk of incident CHD (HR 1.31, 95% CI: 1.13–1.52), as did consistent non-drinkers (HR 1.47, 95% CI: 1.21 –1.78). Amongst consistent non-drinkers, women showed a higher risk of developing CHD than consistently moderate drinkers while their male counterparts did not, said O'Neill.

"The possibility that non-drinkers have increased risk of CHD compared to moderate drinkers is a contentious issue," remarked O'Neill. He added that by using repeat measures of alcohol intake, the study managed to differentiate between former drinkers and non-drinkers, and as such their results for non-drinkers were supportive of the theory that "long-term abstainers do also have higher CHD risk compared to moderate drinkers".

When fatal CHD outcomes were examined alone (secondary aim), only former drinkers had a significantly elevated risk, however consistent non-drinkers showed similar hazard ratios, reported the researchers.

There was no evidence of elevated CHD risk for consistently heavy drinkers (3.8% experiencing a CHD event, of which 0.6% were fatal), and only a weak association with fatal CHD for inconsistently heavy drinkers, attenuated following adjustment for confounding factors. Heavy drinkers, especially women, are often under-represented in study samples, so "estimates of CHD outcomes need to be considered with caution, particularly in light of the known wider health impact of heavy alcohol intake levels," said O'Neill. 

Looking ahead to upcoming work, O'Neill pointed out that, "There are additional characteristics to how people drink that we would however also like to take into account, such as when people binge drink, but information on this is not always measured by every cohort."

O'Neill also added a note of caution in overinterpreting the results in what is a complex issue requiring further inquiry..  "Alcohol intake, even at moderate levels, is known to be associated with other health issues beyond coronary heart disease, such as certain cancers, so it is inadvisable to suggest any form of drinking is good."

Published in the 22 August edition of BMC Medicine.

COI: Dr O'Neill has declared no competing interests


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