Oral contraceptives and the decline in mortality from circulatory disease.
Many publications have claimed that oral contraceptives (OCs) are associated with an increased risk of circulatory disease, yet between the years 1962 and 1976, when OCs became widely used in the United Kingdom, death rates from circulatory disease in women of reproductive age fell steadily. This decreased mortality was greater in young women than in men of comparable age, and did not occur in older women. These data tend strongly to refute the belief that OCs are causative of circulatory disease. The possibility that the decreased mortality rate is due to a protective effect of OCs was examined. It was concluded that they could not be completely responsible, although a partial effect could not be ruled out with certainty. It is suggested that, when mortality trends are opposed to the results of case-control or cohort studies, serious doubts are cast on the conclusions about causal relationships.