Effect of increased warfarin use on warfarin-related cerebral hemorrhage: a longitudinal population-based study.

BACKGROUND AND PURPOSE Warfarin use has rapidly increased with the aging of the population. We investigated the temporal trends in the incidence and outcome of warfarin-related intracerebral hemorrhages (ICHs) in a defined population. METHODS We identified all subjects with first-ever primary ICH during 1993 to 2008 among the population of Northern Ostrobothnia, Finland. The number of warfarin users was obtained from the national register of prescribed medicines kept by the Social Insurance Institution of Finland. We calculated the annual incidence of warfarin-related ICHs, 28-day case fatality, and deaths from the primary bleed. RESULTS The proportion of warfarin users among the population increased 3.6-fold from 0.68% in 1993 to 2.28% in 2008. Of a total of 982 patients with ICH, 182 (18.5%) had warfarin-related ICH. One-year survival rate after onset of stroke was 35.2% among warfarin users and 67.9% among nonusers. The annual incidence (P=0.062) and 28-day case fatality of warfarin-related ICHs (P=0.002) decreased during the observation period. Warfarin users were older (mean difference 6.6; 95% CI, 5.0 to 8.1; P<0.001) than nonusers. Admission international normalized ratio values above the therapeutic range (2.0 to 3.0) decreased through the observation period, suggesting improved control of anticoagulant therapy over time. CONCLUSIONS The annual incidence and case fatality of warfarin-related ICHs decreased, although the proportion of warfarin users almost quadrupled in our population.