Decline in cerebral thromboembolism among young women after introduction of low-dose oral contraceptives: an incidence study for the period 1980-1993.

The aim of this study was to analyze age-specific incidence rates (IRs) of cerebral thromboembolic attacks (CTA) among women and men 15-44 years of age in Denmark from 1980 through 1993 and to quantify possible influences from oral contraceptives (OC) on the incidence figures. The discharge diagnoses ICD 432-436 from all Danish neurological, neurosurgical and medical departments during the period 1980-1993 were identified in a central diagnosis register. The use of OC was achieved from complete sale statistics during the study period and cross-sectional studies assessing the type-specific use of OC at different ages. During the 14-year study period, 2,100 female and 2,552 male attacks were registered. Men had an exponentially increasing IR with increasing age. Compared with men in the period 1980-86, women had more attacks in the 20-35-year age group and fewer attacks above the age of 35. After 1987 the sex differences below the age of 35 were not significant. From the first half (1980-86) to the last half (1987-1993) of the study period, women below 30 years had a significantly falling CTA IR of -20.4%, compared with a non-significant fall of -9.5% among men below 30 years. In the age group above 30 years, women experienced a not significant increase of 4.2%, men a significant increase of 11.4%. Assuming that use of OC implied an average relative risk of CTA 111115 and pregnancy a relative risk of 4, a correction was made for the contribution of incident cases among women. (ABSTRACT TRUNCATED AT 250 WORDS)