Drinking after heart attack studied
“Alcohol can help heart attack victims live longer,” according to The Daily Telegraph. The newspaper said that regularly consuming two alcoholic drinks a day gave heart attack survivors “a 42% lower risk of dying from heart disease” and 14% lower risk of death from any cause compared with non-drinkers.
This story is based on research that looked at just over 1,800 male health professionals who had a first heart attack while taking part in a large 20-year study. Over the course of the study, those who drank an average between 10 to 29.9g of alcohol daily (between about 1-4 UK units) in the period before and after their heart attack had a reduced risk of death from any cause or from cardiovascular causes compared to non-drinkers.
One of the limitations of this study is that men who avoided drinking may have done so because of health reasons. Also, it is difficult to be certain whether alcohol consumption was directly responsible for the changes seen in risk of death. The results may also not apply to women.
Current UK advice is that men should regularly drink no more than 3-4 units of alcohol a day (regularly meaning drinking this amount every day or most days of the week). The moderate levels of alcohol consumption in this study would be broadly within the recommended limits. These findings are not in themselves a reason for anyone who is not a drinker to start drinking.
Where did the story come from?
The study was carried out by researchers from Harvard Medical School and other research centres in the US. It was funded by the US National Institutes of Health and published in the peer-reviewed European Heart Journal.
It was covered by The Daily Telegraph, Daily Mail and the Daily Mirror. The papers generally included warnings about the harmful effects of heavy alcohol consumption and binge drinking to balance out the message.
However, the Telegraph suggested that ‘turning to drink’ can help men live longer after their first heart attack, which is not correct. Men whose alcohol consumption rose after a heart attack had the same risk of death as non-drinkers. This was found once the study broke down the effects according to drinking patterns and took into account other important factors likely to influence their results.
What kind of research was this?
This study was an analysis of data from a larger prospective cohort study called the Health Professionals Follow-up Study (HPFS). It looked at the relationship between long-term alcohol consumption and risk of death in males who had survived their first heart attack. As the name suggested, all the participants were health professionals, such as dentists and pharmacists, meaning their health-related behaviour and attitudes may differ from those seen among the general population.
This study model appears to be the best way of looking at the links between alcohol and death in a period following a heart attack, as it would not be feasible to conduct trials assigning people to drink different levels of alcohol over their lifetime. However, given the observational nature of this study any apparent links between alcohol and death risk could be due to factors other than alcohol consumption, so the researchers need to try to take any potential confounding factors into account in their analyses.
What did the research involve?
In 1986, researchers enrolled a group of 51,529 American men aged 40 to 75 years and assessed their medical history and lifestyles, including their alcohol consumption in the previous year. They recruited dentists, pharmacists, optometrists, osteopaths, podiatrists and vets. They followed them up for 20 years to see who had a heart attack and who did not, who died after their heart attack and cause of death if it was not from a heart attack. The researchers then looked at whether level of alcohol consumption was related to risk of death after a first heart attack.
As well as being assessed at the start of the study, alcohol consumption and other dietary habits were also assessed every four years during follow-up. Reported alcohol consumption was converted to grams of pure alcohol consumed each day. For the purposes of their research the study's authors estimated that one beer contained 12.8g alcohol, one 4oz glass of wine 11.0g, and one shot of liquor 14g.
In the UK the alcoholic content of drinks is also given as units, with one unit equating to 10ml of pure alcohol, weighing 8g. Average daily alcohol use was grouped into 0g alcohol (no drinks), 0.1 to 9.9g (about one drink), 10 to 29.9g (about two drinks), and ≥30g (about three drinks).
Men were asked about their health and other lifestyle factors every two years. The current study excluded any men who had experienced a heart attack before they enrolled in the study. If they reported having a first heart attack during the follow-up period their medical records were obtained from the hospital where they were treated. Deaths were identified from state records, the national death index, or reports from the men’s next of kin or the postal system. Cause of death was identified from medical records or autopsy records.
The researchers first looked at whether level of alcohol consumption was related to risk of death following a first heart attack. They looked at overall average alcohol consumption in the period from the last follow-up session before the heart attack and the period after. They then looked at consumption before and after the heart attack separately to see if the effect of drinking on these two periods was different.
The researchers took into account factors that could influence the results in their analyses. These included age, body mass index (BMI), marital status, smoking status, physical activity, total calorie intake, medication use, history of diabetes and high blood pressure, and family history of early heart attack. The researchers also looked at whether the link varied depending on the severity of the heart attack.
What were the basic results?
Between 1986 and 2006, there were 1,818 men who had a confirmed first non-fatal heart attack.
During a subsequent 20 years of follow-up, 468 of these men (26%) died.
Compared to non-drinkers the risk of death from any cause during follow-up was:
- 22% lower in men who consumed on average 0.1 to 9.9g alcohol daily (hazard ratio [HR] 0.78, 95% confidence interval [CI] 0.62 to 0.97)
- 34% lower in men who consumed on average 10 to 29.9g daily (HR 0.66, 95% CI 0.51 to 0.86)
- not significantly lower in men who consumed on average 30g or more of alcohol daily (HR 0.87, 95% CI 0.61 to 1.25)
Compared to non-drinkers the risk of death from a cardiovascular cause during follow-up was:
- not significantly lower in men who consumed on average 0.1 to 9.9g alcohol daily (HR 0.74, 95% CI 0.54 to 1.02)
- 42% lower in men who consumed on average 10 to 29.9g daily (HR 0.58, 95% CI 0.39 to 0.84)
- not significantly lower in men who consumed on average 30g or more of alcohol daily (HR 0.98, 95% CI 0.60 to 1.60)
Most men did not alter their alcohol consumption after their heart attack. When the researchers looked at how death risk related to pre- and post-heart attack drinking separately they got similar results.
In these analyses the men who drank the lowest levels of alcohol (0.1 to 9.9g alcohol daily) or the highest levels of alcohol (average ≥30g alcohol daily) before or after their heart attack did not differ in their overall or cardiovascular-related mortality risk to non-drinkers. The group who drank a moderate amount of alcohol (on average 10 to 29.9g daily) before or after their heart attack had lower levels of all-cause mortality than non-drinkers.
When looking at subgroups of men with different types and severities of heart attack, they found that the link between moderate alcohol consumption and reduced risk of death appeared to be stronger in men who had less severe impairments in heart function after their heart attack.
How did the researchers interpret the results?
The researchers concluded that in men who survived their first heart attack, long-term moderate alcohol consumption was associated with a reduction in the risk of death, both from any cause and from cardiovascular causes. They say that this effect may be greatest in men with less severe impairments in heart function after their heart attack, and that this needs further study.
There has long been debate over whether alcohol can help prevent health problems such as heart attacks. This new study looked at associations between alcohol intake and the risk of dying following a heart attack. It has suggested that in men who survive their first heart attack, moderate alcohol consumption (between 1-4 UK units daily on average) was associated with a reduced risk of death compared with not drinking alcohol.
This study’s main strengths are its size, length of follow-up, and its collection of data going forward rather than going through existing records. Together these increase its chances of getting reliable information. There are a few points to note:
- The study only included men who had survived a heart attack. It does not tell us about the effects alcohol consumption might have on risk of a heart attack or of dying from a first heart attack.
- As with all studies of this type, factors other than alcohol consumption could be contributing to the differences seen. The researchers took a number of these factors into account but this may not have removed their effect entirely. For example, smoking status was simply recorded as ‘current smoker’ and adjustments may not have adequately reflected the effects of number of cigarettes smoked, or of stopping and starting smoking over the course of the study. Also, the researchers say that socioeconomic status was not adjusted for as the professional groups recruited were from similar backgrounds, although it may have still had an effect.
- The study included only male health professionals, who may have different characteristics to the population as a whole, for example their socioeconomic status. The results may not apply to women or other population groups.
- Alcohol use was self-reported and may be subject to some inaccuracies.
- The comparisons have been made with men who did not drink at all, this may include men who do not drink for health reasons, which could mean they have poorer health to start with.
- Cardiovascular disease is not the only potential risk associated with drinking alcohol, and some groups such as the World Cancer Research Fund say that avoiding alcohol altogether may be the best option for preventing cancer.
- Current UK advice is that men should not regularly drink more than 3-4 units of alcohol a day (with regularly meaning drinking this amount every day or most days of the week). One UK unit of alcohol is 8g, so the moderate levels of alcohol consumption in this study represent between one and four units a day on average, which would be broadly within the recommended limits.
These findings are not in themselves a reason for anyone who is not a drinker to start drinking.
Analysis by Bazian
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