Tuesday March 11 2008
Alcohol should be enjoyed in moderation
The Daily Mail reports that “teetotallers may finally have a reason to enjoy the odd tipple - a new [study] shows non-drinkers who begin drinking in middle-age live longer and are less likely to develop heart disease.” The Daily Mirror also covers the story and says that researchers have found that “former non-drinkers who downed a glass or two a day had 38% less chance of heart disease after four years”.
This story is based on a study in which researchers analysed data from about 7,000 people in the US over a 10-year period. They found that people who started drinking moderately during the first six years of the study were less likely to have a heart attack or stroke during the next four years than those who remained teetotal.
However, as differences between the groups other than drinking habits may have had an affect, these results should be interpreted with caution. It is also important to point out that starting moderate drinking did not have a significant effect on overall deaths, so it is not fair to say that the moderate drinkers “lived longer”.
People who reach middle age who have never drunk alcohol and have no medical reason not to, may start drinking moderate amounts with few risks and possible benefits to their health. However, they should keep within current recommended levels and be aware of the risks. Starting drinking for the sole reason of reducing the risk of cardiovascular events seems premature at this stage.
Where did the story come from?
Dr Dana E. King and colleagues from the Medical University of South Carolina carried out the research. The study was funded by the National Heart, Lung and Blood Institute. The study was published in the peer-reviewed medical journal: The American Journal of Medicine.
What kind of scientific study was this?
This was an analysis of data from a prospective cohort study - the Atherosclerosis Risk In Communities study (ARIC) - that enrolled 15,792 people from four communities in the US between 1987 and 1989, and followed them up until 1998. The participants, aged between 45 and 64 years old, provided information about their health and lifestyle in annual telephone calls and three visits (once every three years) during this period.
From the ARIC participants, the researchers identified people who did not drink when they joined the study, or have a history of cardiovascular disease (heart attack, heart surgery or associated artery surgery and stroke) during the first six years of follow up. The researchers then looked at whether they starting drinking alcohol during the first six years of follow up, how much they drank, and what they drank (beer, wine, spirits). Moderate alcohol consumption was defined as 1-14 drinks a week for men and 1-7 drinks for women.
They then identified those people who had developed cardiovascular disease or died from it during the last four years of follow up, and compared the proportion of people who had started drinking to those who had remained teetotal. The researchers adjusted these analyses for factors other than drinking that might affect risk of cardiovascular disease, including “demographic, lifestyle factors, and disease histories” as recorded at the six-year follow up.
What were the results of the study?
Of the 7,359 people interviewed at six years who were teetotal at the start of the study, 6% had started drinking moderately, and 0.4% had started drinking heavily. People who had started drinking moderately were more likely to be white, male, educated to high school level or above, regular exercisers, and with no history of diabetes, high blood pressure, or high cholesterol.
Fewer people who began drinking moderately experienced a cardiovascular event (6.9%) than people that remained non-drinkers (10.7%). This was equivalent to a reduction of 38% in the odds of having an event during the four years of follow up. There was no difference in the rate of death between the groups.
What interpretations did the researchers draw from these results?
The researchers concluded that starting to drink moderate amounts of alcohol in midlife significantly reduced the risk of cardiovascular events after four years. They caution that this benefit must be weighed up against the known dangers of alcohol consumption. They suggest that further prospective studies are needed.
What does the NHS Knowledge Service make of this study?
This was a large study, but a number of limitations must be taken into account:
- With this type of study, the main limitation is that the differences in cardiovascular disease that were seen may be due to differences between the groups other than their drinking habits. For example, the people who started drinking were more likely to be regular exercisers, and to not have high blood pressure, diabetes, or high cholesterol. Although the authors state that their calculations took into account some factors that might influence and bias the results, it was not clear which factors these were, and these adjustments might not fully remove the effects of these factors. The authors also would not have been able to adjust for unknown factors, or unmeasured factors (such as diet) that might have had an effect. For this reason, it is best to interpret these results cautiously.
- This study did not report on people’s reasons for not drinking. The people who were teetotal may have had medical reasons for doing so, and these reasons might affect or be linked to their cardiovascular risk.
- The participants reported their alcohol consumption themselves, and this was assessed retrospectively each year. People’s reports of their drinking may not be accurate, either because they cannot remember or because they are concerned about what people will think about their responses.
- The study only had a relatively short period of follow up, and differences between groups might not be apparent over longer periods.
Starting drinking solely to reduce the risk of cardiovascular events seems premature at this stage. But people who have reached middle age and wish to start drinking for their own enjoyment and have no medical reason not to, then should do so moderately, and be aware of the risks.
Sir Muir Gray adds...
I see no reason to advise people to start drinking alcohol. If middle aged people need advice they should be advised to walk an extra 3000 paces a day.