Risk of haemorrhagic stroke in patients with oral anticoagulation compared with the general population

Objectives. To compare the incidence of haemorrhagic stroke (HS), and the risk of fatal outcome after HS in patients with oral anticoagulation (OA) treatment and in the general population. Design. Five-year cohort study. Setting. The Anticoagulation Clinic, Malmo University Hospital, Lund, Sweden. Subjects. A total of 4434 patients treated with OA (6693 treatment years) from 1 Oct 1993 to 30 Sept 1998. The population-based Stroke Register of Malmo, Lund, Sweden (STROMA). Results. Forty-eight patients had HS according to ICD 9 code 430 and 431. HS occurred at a higher age in women compared with men (mean age 79.5 years vs. 74.7 years, P = 0.009). The age-adjusted relative risk of HS during OA treatment was 10.9 (CI 6.7-17.6) for men and 9.3 (CI 5.7-15.0) for women, as compared with the untreated general population. Number needed to harm (NNH) (person-years) was 103 for men and 188 for women. Adjusted for age and sex, OA treatment was significantly associated with fatal outcome in patients with HS (OR = 2.6, CI 1.4-4.8). Conclusions. Patients with OA treatment had approximately 10 times higher risk of HS as compared with the general population, and the risk increased markedly with age. OA treatment is associated with an increased case fatality in patients with HS.