Oral contraceptives and heart attack: results of the MICA case control study by Dr Erik Skovenborg

A negative association between light to moderate alcohol consumption and the risk of coronary heart disease has been documented in numerous ecological, case-control and cohort studies. The observed association is in the order of a 40-60 % reduction in risk among light to moderate drinkers.it has often been claimed, that only the hearts of middle aged and older men benefit by a moderate alcohol consumption, however data from large cohort studies like the Copenhagen City Heart Study show, that women who consume small to moderate amounts of alcohol are protected from coronary heart disease (CHD) as much or more than men, with relative risks versus non-drinkers of 0.3 - 0.8.

Now results from the MICA case-control study reported in British Medical Journal (BMJ 1999;318:1579-84) tell us about the hearts of women aged between 16 and 44. Nicholas Dunn from London School of Hygiene and Tropical Medicine and his co-workers used a community based case-control study to determine the association between myocardial infarction (MI) and use of different types of oral contraception in young women. 448 cases were recruited from women aged between 16 and 44 who had suffered an incident myocardial infarction. Controls were women without a dianosis of MI matched for age and general practice.

As expected myocardial infarction is rare in this age group of women: the incidence rate was 0.5 per 1000 women years. There was no significantly increased risk of MI in users of oral contraceptives, which is encouraging. Amongst the women who did suffer a heart attack, 88% had one or more known cardiovascular risk factors; 80% were smokers and the study showed that 73% of acute MI in women of reproductive age could be prevented if women stopped smoking. That is certainly something to think about.

The women were also asked about their intake of alcohol, and the beneficial effect of consumption of alcohol is in keeping with results of other studies. In this group of women of reproductive age, where the rate of MI was very low, the odds ratio for MI of women with an intake of alcohol 2-3 days per week was 0.54 (0.41 to 0.72). That is almost exactly the same protection as the benefit of exercise 2-3 hours per week: odds ratio 0.55 (0.43 to 0.82).

Dr Erik Skovenborg is a member of the Scandanavian Medical Alcohol Board, author of Wine and Health - myths and facts and a member of the AIM editorial board.