Warfarin sodium therapy in patients with atrial fibrillation markedly reduces the incidence of embolic stroke. However, in elderly patients warfarin therapy is often underused owing to the perceived higher risk of hemorrhagic complications.
To assess the quality of anticoagulant control and the incidence of hemorrhagic complications and stroke in an elderly population (>75 years old) compared with a younger control group (between 60 and 69 years) and to assess the quality of anticoagulant control and incidence of hemorrhagic complications in those patients who recently commenced receiving warfarin therapy (first year of therapy).
Patients and Methods
In this retrospective follow-up study, anticoagulant control and the incidence of hemorrhagic complications and stroke were assessed in an elderly population (>75 years old) compared with a younger control group (between 60 and 69 years), all with atrial fibrillation(target international normalized ratio [INR] 2.5) and attending a hospital outpatient anticoagulant clinic.
A total of 328 patients were studied over a 21-month period. There were 204 patients in the control group providing 288 patient-years of follow-up and 124 patients in the elderly group providing 170 patient-years of follow-up. The percentage of INR results in the target range was not statistically significantly different between the elderly and control groups (71.5% vs 66.1%) and the occurrences of incidences of INR greater than 7 were 4.2% in the control group and 4.7% in the elderly group (P = .96). The incidences of major hemorrhage were 2.8% per year in the elderly group and 2.9% per year in the control group (P = .96); overall incidence was 2.8% (95% confidence interval, 1.3%-4.4%). One hundred one of the 328 patients studied commenced warfarin therapy during or within 3 months of the start of the study. In this induction group, 62.1% of INRs were within the target range compared with 70.9% of INRs in patients who had been receiving warfarin therapy for more than 3 months at the start of the study (P = .002). The incidences of INR greater than 7 and major hemorrhage were 7.9% per year and 6.9% per year, respectively, in the cohort who recently began warfarin therapy compared with 3.4% per year and 1.7% per year in the group who were receiving warfarin therapy for more than 3 months.
While it was impossible to consider any selection bias at the level of referral to the clinic, these findings suggest that the elderly population attending our anticoagulant clinic did not have poorer anticoagulant control or an increased incidence of hemorrhage while receiving warfarin therapy.