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KMID : 0869620110280020142
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Journal of Korean Society of Hospital Pharmacists
2011 Volume.28 No. 2 p.142 ~ p.152
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Incidence Rate and Risk Factors of Bleeding Associated with Warfarin Therapy in Elderly Atrial Fibrillation Patients
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Cho Hyun-bok
Min Kyoung-A
In Yong-Won
Lee Young-Mee
Sohn Gee-Ho
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Abstract
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Atrial fibrillation is an independent risk factor for stroke, and oral anticoagulation therapy with warfarin is effective in the prevention of stroke in atrial fibrillation. It has been reported that the prevalence of atrial fibrillation increases with age, and numbers of elderly patients who take warfarin is also increasing. As a result, increasing rate of bleeding associated with warfarin in elderly patients has been reported in previous studies. This study was designed to evaluate the incidence rate of bleeding in relation to age, and the factor associated with bleeding. In this retrospective study, baseline characteristics, anticoagulant control (target INR of 2-3) and the incidence of bleeding were assessed in an elderly population (≥75 years) compared with a younger population (between 65 and 74 years). All patients were new warfarin users, attending anticoagulation service (ACS) at Samsung Medical Center from January 1, 2008 to August 31, 2009. Each patient was followed up by 1 year after starting taking warfarin. A total of 155 patients were studied, and 100 patients in the younger group providing 83.1 person-years of follow-up and 55 patients in the elderly group providing 39.5 person-years of follow up. Between younger and elderly group, average of duration of INR within target range is 57.5% and 61.5% respectively, and there is no significant difference (p=0.269). No difference of incidence of minor bleedings was found between the elderly group and the elderly group(p=0.395). Major bleedings were developed 1 event in younger group and 2 events in the elderly group. Incidence rate of major bleeding in the elderly group was higher than the younger group in 4.21 folds, but it was not statistically significant (95% CI, 0.38-46.4). 42.6% of all bleeding and 33.3% of major bleeding were developed in first 90 days after starting warfarin therapy. Male (p=0.031) was analyzed as a risk factor for bleeding associated with warfarin in the all 155 patient, and history of cancer was analyzed that had effect on the analyzing sex as a risk factor for bleeding. However, we couldn’t find the risk factors of bleeding for the elderly group. These findings suggest that older age and early period of warfarin therapy were related to increasing of bleeding caused by warfarin, and needed much care for anticoagulation therapy. Further studies to analyse risk factors for bleeding and there results may be help provide better anticoagulation therapy to elderly atrial fibrillation patients for prevention of stroke.
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KEYWORD
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atrial fibrillation, older age, bleeding associate with warfarin, risk factors
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