Several epidemiological studies have demonstrated at the individual level an elevated risk of cardiovascular death for women who have been using oral contraceptives. Nevertheless, there has been no detectable increase in the number of cardiovascular deaths during the last fifteen years in countries where the use of oral contraceptives has become widespread. In this paper, we have tried to analyse this apparent contradiction and to discuss the causal nature of the relationship linking oral-contraceptives and cardiovascular death. For this purpose, we present a bibliographical summary of the relevant studies as well as an analysis of the trend in cardiovascular deaths among women in France from 1968 to 1975.
PIP: This paper analyzes why there has been no detectable increase in the number of cardiovascular deaths in the last 15 years in countries where oral contraceptives (OC) use is widespread, despite the elevated risk of cardiovascular death among OC users demonstrated by epidemiological studies. 2 cohort studies in Great Britain, the Royal College of General Practitioners Study and the Oxford Family Planning Association Study, showed that cardiovascular mortality was higher among OC users. The observed excess mortality concerned primarily non-rheumatoid cardiopathy and hypertesion with a relative risk of 4 after standardization. Cardiovascular pathology of all types primarily affected women over 35. A number of case control studies confirmed the excess cardiovascular morbidity and mortality among OC users. Most studies found relative risks to remain significant when confounding factors such as hypertension, smoking, diabetes, and obesity were controlled. Results of attempts of assess the influence of duration of OC use on cardiovascular mortality have been inconsistent. Studies attempting to determine whether cardiovascular mortality on a societal level has increased in the female age cohorts affected by OC use have had to face the methodoligical problem that cardiovascular mortality in general is falling, so that there is no adequate reference population. Such studies have failed to demonstrate an evevation of female cardiovascular mortality in the past 20 years in countries where OC use is widespread. An examination of trends in cardiovascular deaths among women in France between 1968 and 1975 which took particular account of age similarly failed to demonstate such a relation. The most likely hypothesis to explain the discrepancy is that physicians have been increasingly successful in identifying specific women at risk and at avoiding prescription of OCs for them.