Absolute risk of ischemic and hemorrhagic stroke in Danish women using oral contraceptives

Objective Uncertainty exists for the absolute risk of ischemic and hemorrhagic stroke in users of oral contraceptives (OCs). Estimates greatly vary between countries. In Denmark, absolute risk of ischemic stroke (IS) is estimated to be 21 per 100,000 person-years. Risk of cerebral hemorrhage (CH) is unknown. Using the Danish Stroke Registry, we investigated absolute risk of IS and CH in users of OC. Material and Methods For the Danish female population aged 15-49 years during 2003-2011, we obtained information on hospital admission for IS and CH and current use of OC from Danish nationwide registries. We defined current use of OC as redeeming at least two OC prescriptions within the previous year. Results The Danish female population years 2003-2011 consisted mean of 1,246,142 women per year. Of these, 29.6% were OC users. In the study period, OC users had 291 IS and 14 CH. Absolute risk of IS in OC users was 8.8 per 100,000 person-years and of CH it was 0.4 per 100,000 person-years. Conclusions In OC users, absolute risk of IS was 8.8 per 100,000 person-years. This is more than half that of the risk previously assumed in Denmark. Risk of CH in OC users was very low and 0.4 per 100,000 person-years.