Absence of correlation between oral contraceptive usage and cardiovascular mortality.

Oral contraceptive (OC) usage and cardiovascular mortality rates for all women (and men) of reproductive age, but specifically for those aged 35-44 years, were examined in the United Kingdom. These data show: OC-usage increased from 14.1 million packs in 1968, to 45.1 million in 1976, decreasing to 37.1 million in 1980. Ischaemic heart disease (IHD) mortality rates for the years 1968-1980 for women of reproductive age of 15-34 years were stable: for those aged 35-44 years the rates fell gradually by 19%. Mortality rates for all types of cerebrovascular disease (CVD) for 1969-1978 remained stable for women of 15-34 years, but for women of 35-44 years rates for subarachnoid haemorrhage and cerebral haemorrhage (the two largest groups) declined by 11% and 34% respectively. The absence of a positive correlation between OC usage and cardiovascular mortality rates is difficult to explain if OCs are the cause of fatalities, as claimed by some epidemiological studies. Possible counteracting variables--such as decreased ascertainment or decreased usage by women of 35-44 years, or decreased relative risk over the time period--which might account for this paradoxical result, were examined but discarded as being unlikely. Evidence from other data--e.g. the similarity of male and female mortality rates for each group, the increased mortality rates for women of 45-54 years (who do not take OCs), and the similarity of mortality rates in women in years when OC-usage was widely different--all suggest that a counteracting variable does not exist. The data on cardiovascular mortality rates in the UK, showing an absence of positive correlation with OC-usage, are thus opposed to the conclusions of epidemiological studies claiming an increased risk of cardiovascular mortality due to OCs, and specifically contradict the claim that such increased risk is found in 35-44 year-old OC-users.