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A new study has refuted the opinion that moderate alcohol consumption protects against strokes and heart attacks
Dmitry Mazalev, Naked Science
Despite the fact that the negative effect of alcohol on the human body is beyond doubt, some past studies have argued that moderate alcohol consumption creates a protective effect, reducing the chance of myocardial infarction and stroke. The results of a new genetic study involving half a million people and published in The Lancet (Millwood et al.,
(Conventional and genetic evidence on alcohol and vascular disease aetiology: a prospective study of 500,000 men and women in China), this connection is refuted.
"The use of genetics is a new way to assess the effects of alcohol on health and a good opportunity to find out whether moderate alcohol consumption really creates a protective effect: the genetic analyses carried out helped us to identify the cause-and–effect relationships of this phenomenon," says lead author of the study Dr. Iona Millwood.
A joint group of scientists from Oxford University, Peking University and the Chinese Academy of Medical Sciences conducted a large-scale study that involved more than half a million residents of ten regions of China who were asked about alcohol consumption and monitored their physical condition for ten years. Two genetic variants – rs671 and rs1229984 – were measured in more than 160 thousand (161,498 people) of them, which significantly reduce alcohol consumption.
Graph of the ratio of the amount of alcohol consumed and the probability of ischemic stroke (A), hemorrhagic stroke (B) and stroke in general (C) according to epidemiological analysis / © The Lancet
After that, the scientists divided the participants into nine groups, for each they established indicative profiles of alcohol consumption: for example, among homozygous carriers of rs671, only one percent of drinkers who consumed an average of three grams of alcohol per week were identified. As a result of the analysis, a link was found between alcohol consumption and blood pressure: systolic blood pressure increased by 4.5–5 millimeters in accordance with every 280 grams of alcohol per week.
The chances of having a stroke increased with the amount of alcohol consumed: the probability of ischemic and hemorrhagic stroke increased by 27 and 58 percent, respectively, for every 280 grams of alcohol per week. According to the data, alcohol can be called the cause of eight percent of ischemic and 16 hemorrhagic strokes.
Graph of the ratio of the amount of alcohol consumed and the probability of ischemic stroke (D), hemorrhagic stroke (E) and stroke in general (F) according to the data of genetic epidemiological analysis / © The Lancet
Based on the data obtained, the authors conclude that alcohol increases the risk of stroke by about a third (35%) for every four additional drinks per day (280 grams of alcohol per week), without demonstrating any protective effects from moderate alcohol consumption.
"There is no protective effect from stroke with moderate alcohol consumption: even small amounts of it, on the contrary, increase the risk, and in the future we plan to collect more evidence," says co–author of the study, Professor Zhengming Chen.
In China, women do not drink alcohol as often (less than two percent of the women in the study drank for most weeks, and when they drank, they consumed significantly less than men), and genetic variants that cause alcohol intolerance had little effect on blood pressure or stroke risk. Thus, the women in this study represented the necessary control group, which helped to confirm that the impact of these genetic variants on the risk of stroke in men was caused by alcohol consumption, and not by any other mechanism.
The authors emphasize that it would be impossible to conduct such a study among the population of Western countries, where almost no one has the appropriate genetic variants, but these conclusions about the influence of alcohol in Asia should be applicable worldwide.
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