Oral Contraceptives and Myocardial Infarction

Studies done in the United Kingdom suggest a correlation between ora l contraceptive (OC) use and increased risk of myocardial infarction (MI ). A study of 153 women under 50 years of age who died of MIs as compar ed with a control group of the same age and marital status showed a significant association between OC use and MI which became stronger with increasing age: e.g., risks for the 30-39 and 40-44 year-old groups were 2.8 and 4.7 respectively. Another study involving 63 MI survivors between 25 and 44 years of age compared with a similar control group showed a strongly positive association: 29% of the patients and 8% of the controls used OCs and risks for the 30-39 and 40-44 year old groups were 2.7 and 5.7 respectively. The risk in OC users was 4.5 times greater than in nonusers. Other risk factors such as diabetes, cigarett e smoking and obesity also have a positive association with MI. Only one of 17 OC users at the time of MI had no other identified risk factor . When ranked according to the number of risk factors present (includin g OCs) risks relative to women in whom none were present were 4.2 for 1 factor, 10.5 for 2 factors and 78.4 for 3 or more factors. These estimates suggest that in women under 45 years of age, OCs act synergist ically with other risk factors rather than additively, to produce MI. Stroke, also identified, did not appear as a result of a synergistic relationship between OC and other risk factors comparable to that found in relation to MI. Further study is needed but estimated incidence rates of fatal and nonfatal MI attributable to OC use are each about 3.5 per 100,000 30-39 year old users per year and each about 45 per 100,000 40-44 year old users per year. Women with more than 1 risk factor for MI should consider alternative methods of contraception. Those women who do use OCs regularly, especially older women, should be followed closely and advised against OC continuation.