Oral Contraceptives, Smoking and Risk of Myocardial Infarction in Young Women

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Abstract
The use of oral contraceptives (OC) and smoking habits were studied by using a questionnaire in a random population sample of women from two counties of Eastern Finland in 1972. The participation rate was 95%. Data on use of OC and smoking were collected for 2 653 women aged 35–49 years. During the next seven years, 27 of them had developed an acute myocardial infarction (AMI). Smokers had a 2.6‐fold (95% confidence interval (CI)=1.2–6.0) crude risk of developing AMI compared with non‐smokers. Women taking OC had a 1.3‐fold (95% CI=0.4–6.9) risk of developing AMI compared with those who did not. Women who both smoked and used OC had a 7.2–fold (95% CI=2.1–24.7) risk of AMI compared with non‐smokers and non‐users of OC. The results indicate that use of OC is associated with an excessive risk of AMI among female smokers.