A prospective study of age at menarche, parity, age at first birth, and coronary heart disease in women.

Reproductive events in women are associated with alterations in blood lipids and blood pressure and may therefore influence determinants of coronary heart disease. To investigate the risk of coronary heart disease in relation to age at menarche, parity, and age at first birth, the authors evaluated prospectively the experience of 119,963 US women aged 30-55 years who were free from coronary heart disease in 1976 and were followed through 1982. During 700,809 person-years of observation, 308 incident cases of nonfatal myocardial infarction or fatal coronary heart disease occurred. Younger age at menarche was weakly associated with coronary heart disease (age-adjusted rate ratio of 1.3 for menarche before age 11 years compared with menarche at age 13 years; chi, Mantel extension test for trend = -1.1, p = 0.2). Nulliparous women experienced only a slightly higher rate of coronary heart disease than parous women (rate ratio = 1.2, 95 per cent confidence interval 0.8-1.8). Among parous women, there was no alteration in risk with increasing number of births. Likewise, there was no significant association between age at first birth and coronary heart disease (chi, Mantel extension test for trend = -0.4, p = 0.4). Established risk factors for coronary heart disease nevertheless showed expected relations. These findings show no important association between reproductive experiences and risk of coronary heart disease.