The purpose of this study has been to chart the changes in usage of different types of oral contraceptives (the pill) throughout the 1980's, as well to estimate the extent to which these changes can be expected to influence the incidence of cerebral thromboembolic attacks amongst fertile women. The use of different types of the pill and smoking habits in different age groups are also investigated. The work is based om cross-sectional studies during the period 1980-1990; the use of the pill is documented by national sales statistics from 1980-1990 as well as from questionnaires answered by 1370 healthy women from 1990. The total sale of the pill has been fairly stable throughout the decade, corresponding to a theoretical user percentage of 23-26. The proportion of pills sold containing 50 micrograms oestrogen has fallen steadily from 51% in 1980 to 11% in 1990, while the proportion of pills containing 30-40 micrograms oestrogen (this group includes the mulit-phase pills) has doubled from almost 40% to almost 80% over the same period. Finally, the proportion of minipills has fallen from 10% to 5%. It is estimated that the changed distribution in use of the different types of the pill through the eighties can be expected to reduce the incidence of cerebral thromboembolic attacks among fertile women by 4.5%. Since the 95% confidence limits on the incidence of such attacks among fertile women in Denmark is +/- 14%, one cannot expect to show significant changes in the total incidence of cerebral thrombo-embolic attacks among these women as a consequence of the change in contraceptive pill profile.(ABSTRACT TRUNCATED AT 250 WORDS)
