Objectives: To estimate the incidence of bleeding leading to death or hospital admission in out-patients treated with oral anticoagulants.
Design: Population-based historical cohort study 1 January 1992 to 31 September 1994.
Setting: The County of North Jutland, Denmark (488,000 inhabitants).
Subjects: Six hundred and eighty-two consecutive patients commencing oral anticoagulant therapy.
Main outcome measures: Fatal bleeding or bleeding demanding hospital admission.
Results: In 756 treatment-years of follow-up, there were 45 major haemorrhagic events (6.0 per 100 treatment-years) in 42 patients, of which seven (0.9 per 100 treatment-years) were fatal. The risk of a first major haemorrhagic episode was highest during the first 90 days of treatment compared with duration above one year (incidence rate ratio, IRR, 1.9; 95% CI, 0.8-4.1). The rate was highest above the age of 60 years, 6.8 per 100 treatment-years, compared with 2.9 per 100 treatment-years below 60 years (IRR 2.3; 95% CI, 1.0-5.6). The rate for a bleeding event was slightly higher in females than in males (IRR 1.3; 95% CI, 0.7-2.3), but did not vary according to type of anticoagulant drug.
Conclusions: The reported rates of major bleeding in this routine community setting implied a higher bleeding risk than was found in randomized trials or when patients are monitored in specialist anticoagulation clinics.