‘Binge drinking doubles heart risk,’ BBC News reported today. This study was in nearly 10,000 men aged 50 to 59 without heart disease from France and Northern Ireland. Most French men drank regularly (90%) compared to half of Irish men. However, Irish men were more likely to binge drink than French men (9.4% compared to 0.5%).
The combined outcome of heart attack or death from heart attack over 10 years was observed in 5.3% of men from Belfast and 2.6% of men from France. Risk was doubled for binge drinkerscompared to men who drank alcohol at least one day a week, but did not binge drink. Compared to regular drinkers, non-drinkers also had a doubled risk of heart attack or death from heart attack, and former drinkers had an apparent tripled risk.
The study has a few limitations, but the adverse health effects of binge drinking are well established and these results are probably reliable. Men are advised to drink no more than 21 units a week (no more than four units a day), and women should drink no more than 14 units a week (no more than three units a day). Binge drinking (more than eight units a session for men and more than six for women) should be avoided.
Where did the story come from?
The study was carried out by researchers from Toulouse University School of Medicine, other institutions in France, and Queen’s University, Belfast. Funding was provided by grants from the Institut National de la Santé et de la Recherche Médicale (INSERM) and the Merck, Sharp & Dohme-Chibret Laboratory. The study was published in the peer-reviewed British Medical Journal.
Both BBC News and The Telegraph focused on the hazards of binge drinking. However, the research findings were not as straightforward as this because never drinkers and former drinkers were also at an increased risk of heart attack compared to regular drinkers.
What kind of research was this?
This cohort study investigated how different patterns of alcohol intake affect the risk of heart disease. It examined separate study populations in Northern Ireland and in France, due to the typically different lifestyles of these countries.
A cohort study is usually the best study design to investigate the association between an exposure that occurs in daily life (in this case alcohol) and an outcome (in this case heart disease). Limitations may arise, however, in accurately quantifying how much a person drinks. A person’s consumption at the start of the study may not reflect their previous or future consumption. Participants also needed to be checked that they did not have heart disease at the time of assessment, something that may not be certain in all cases.
Potential confounders – factors that can affect results – also need to be taken into account. Therefore, attributing alcohol consumption as the cause of heart disease may be difficult.
What did the research involve?
This study enrolled 9,778 men between 1991 and 1994, with an average age between 50 and 59. Of these, 2,745 were recruited in Belfast, Northern Ireland (from industry, the civil service and general practice). The others were recruited from three areas in France (Lille , Strasbourg , and Toulouse , through free medical health screening and occupational medicine settings).
At the beginning of the study, all men completed health and lifestyle questionnaires, which included their alcohol consumption. The London School of Hygiene & Tropical Medicine Cardiovascular Questionnaire for Chest Pain on Effort and Possible Infarction (the Rose questionnaire) was used, which is a validated tool to evaluate chest pain. They also had BMI, blood pressure and blood cholesterol measured and an electrocardiogram (ECG) recording. Heart disease was established based on either a prior diagnosis by a physician, ECG evidence of past heart attack, or a positive Rose chest pain questionnaire.
Weekly alcohol consumption, assessed once by questionnaire, took into account frequency of consumption, times of day alcohol was drunk, and types of beverage and their alcohol content (e.g. 10% wine, 12% wine, 4% beer, or 5% beer). One drink of alcohol was standardised as 10-12g of ethanol. The participants were then categorised into the following groups:
- never drinkers
- former drinkers
- regular drinkers (men who drank alcohol on at least one day a week, and, if drinking on only one occasion, consumed less than 50g of alcohol)
- binge drinkers (alcohol >50g on at least one day a week)
Follow-up was by annual letter or telephone call, and participants were asked to complete a clinical event questionnaire, including hospitalisations, medical consultations, and so on. Possible coronary events were confirmed by further follow-up of medical records. Death certificates were examined where necessary. The relation between characteristics at the start of the study and major coronary events (heart attack or death due to heart disease), was then analysed.
What were the basic results?
About 50% of men in Belfast and 90% of French men reported drinking regularly, with an average daily consumption of 40.2g in Belfast and 36.4g in France. In Belfast, 12% of men drank daily compared to 75% of French men who drank daily. Only 0.5% of French men (33 out of 7373) were classified as binge drinkers, compared with 9.4% of men in Belfast (227 out of 2405). Non-drinkers (including never and former drinkers) comprised 39.5% of men in Belfast and 9.4% of men in France.
Over an average 10 years of follow-up, 5.3% of the men in Belfast suffered either heart attack or related death, compared to 2.6% of the men in France (combined - 3.3%  of the total 9,778 sample). A further 3.7% of the total sample (361 men) developed angina (chest pain related to heart disease).
Annual incidence of hard coronary events was 5.63 per 1,000 ‘person years’ (the total sum of the number of years that each member of a study population has been under observation) in Belfast and 2.78 per 1,000 person years in France. After adjusting for recognised cardiovascular risk factors and country of study, binge drinkers had almost double the risk of major coronary events compared to regular drinkers (hazard ratio 1.97, 95% confidence interval [CI] 1.21 to 3.22). Never drinkers and former drinkers also had greater risk compared to regular drinkers (hazard ratios 2.03, 95% CI 1.41 to 2.94, and 1.57, 95% CI 1.11 to 2.21, respectively).
How did the researchers interpret the results?
The researchers conclude that regular and moderate alcohol intake throughout the week is associated with a low risk of heart disease, whereas a binge-drinking pattern confers a higher risk.
This research assessed 9,778 men in Northern Ireland and France over an average period of 10 years. It has several strengths including its large size, consideration of various possible confounders, and confirmation of heart disease and heart disease events during follow-up using medical records and death certificates. However, there are still some points that need to be taken into account:
- Alcohol consumption was only assessed once, and it is not known whether this measurement represents the participant’s previous or future consumption. Also quantifying the exact alcohol content of beverages can be difficult, and people may be reluctant to report their true levels of alcohol consumption. Therefore, there may be some inaccuracy when categorising people according to their alcohol consumption.
- Though the researchers took great care to exclude anyone with heart disease when they were enrolled, it is still difficult to ensure that all participants were completely free of heart disease. A person was considered to have no heart disease if they had a never been diagnosed by a doctor, had no ECG evidence of heart disease, and gave a negative response to questions on chest pain and discomfort. However, there are various symptoms of heart disease, and sometimes a heart attack can occur suddenly in a person with no prior evidence of the condition.
- Though the news focused on the doubled risk of heart attack in binge drinkers, it should be noted that this was compared to regular drinkers (men who drank alcohol on at least one day a week, and, if drinking on only one occasion, consumed less than 50g of alcohol). Compared to regular drinkers, non-drinkers also had a doubled risk of heart attack and former drinkers had an apparent tripled risk. This complex ‘U-shaped’ relationship between alcohol and cardiovascular risk has also been observed in other studies.
- Many factors affect the risk of heart disease, and separating the effects of these factors is difficult. Although the researchers attempted to take into account factors that could affect results (potential confounders), some were not included, such as diet. They acknowledge that ‘it is difficult to conclude whether the pattern of alcohol intake has a major role in the incidence of ischaemic heart disease independent of other behaviours, such as diet’.
- The study was carried out in men, and so the results may not be directly applicable to women. The average age of the men was also 50-59, so in younger men there may not be the same association between binge drinking and heart disease.
Men are advised to drink no more than 21 units of alcohol a week (no more than four units a day), and women should drink no more than 14 units of alcohol a week (no more than three units a day). One unit is considered to be 8g by weight of alcohol. Binge drinking (more than eight units a session for men and more than six for women) should be avoided.