THE RISK FOR AND SEVERITY OF BLEEDING COMPLICATIONS IN ELDERLY PATIENTS TREATED WITH WARFARIN

Objective: To determine whether increasing age is associated with an i ncreased risk for bleeding during warfarin treatment. Design: Combined retrospective and prospective cohort studies. Setting: 6 anticoagulat ion clinics. Patients: 2376 patients receiving warfarin for various in dications. Measurements: Bleeding events categorized as minor (resulti ng in no costs or consequences), serious (requiring testing or treatme nt), life-threatening, or fatal. Results: 812 first bleeding events (4 fatal, 33 life-threatening, 222 serious, and 553 minor) occurred duri ng 3702 patient-years. Age was inversely related to the mean warfarin dose and dose-adjusted prothrombin time ratio. The unadjusted incidenc e of minor bleeding complications did not vary according to age group: 18.0 per 100 patient-years for patients younger than 50 years of age, 21.5 for patients 50 to 59 years of age, 24.0 for patients 60 to 69 y ears of age; 23.5 for patients 70 to 79 years of age, and 16.3 for pat ients 80 years of age and older. The unadjusted incidence of serious b leeding complications also did not vary according to age group: 9.3 pe r 100 patient-years for patients younger than 50 years of age, 7.1 for patients 50 to 59 years of age, 6.6 for patients 60 to 69 years of ag e, 5.1 for patients 70 to 79 years of age, and 4.4 for patients 80 yea rs of age and older. The unadjusted incidence of life-threatening or f atal complications combined was significantly higher among the oldest patients: 0.75 per 100 patient-years for patients younger than 50 year s of age, 0.97 for patients 50 to 59 years of age, 1.10 for patients 6 0 to 69 years of age, 0.68 for patients 70 to 79 years of age, and 3.3 8 for patients 80 years of age and older. Patients 80 years of age and older had a relative risk of 4.5 (95% CI, 1.3 to 15.6) compared with patients younger than 50 years of age. After adjustment for the intens ity of anticoagulation therapy and the deviation in the prothrombin ti me ratio using Cox and Poisson regression, age was not generally assoc iated with the occurrence of bleeding; relative risk estimates ranged from 0.99 to 1.03 per year of age (lower-bound 95% CI, 0.97 to 1.01; u pper-bound 95% CI, 1.00 to 1.09). The single exception was life-threat ening and fatal complications in patients 80 years of age or older (re lative risk, 4.6 [CI, 1.2 to 18.1]). Conclusions: Age did not appear t o be an important determinant of risk for bleeding in patients receivi ng warfarin, with the possible exception of age 80 years or older. The intensity of anticoagulation therapy and the deviation in the prothro mbin time ratio were much stronger predictors of risk for bleeding.