Body mass index predicts major bleeding risks in patients on warfarin

Despite the lack of an optimum dosing strategy in obese patients, warfarin remains the most commonly used anticoagulant. Body mass index (BMI) >30 has been linked to increased time to obtain a therapeutic international normalized ratio on initiation of warfarin as well as higher maintenance dose. Despite higher dosage requirements, few studies have examined the relationship between warfarin and bleeding events in obese individuals. We examined the performance of BMI in predicting the incidence of bleeding at an anticoagulation clinic (ACC) over a 1 year period. Eight hundred and sixty-three patients followed in the ACC over a 1 year period were evaluated for bleeds in relation to BMI [defined as weight (kg)/height (m²)]. Seventy-one of the 863 patients had a bleeding event (8.2 %); mean age 69.5 years and 44 % females. BMI categories were normal weight (21 %), overweight (38 %), obese class I (21 %), II (9 %), and III (11.3 %), respectively. Prevalence of major and minor bleeding events were 4.4 and 3.8 %, respectively. In univariate analyses, hazard ratio (HR) for major bleeding risks increases with higher obesity categories (HR 1.3, 1.85, and 1.93 for classes I, II, III, respectively). In multivariable adjusted model obesity classes II and III significantly increased the risk of major bleeds (HR 1.84, p < 0.001). Bleeding risk is higher in obese compared to normal weight individuals who are on warfarin. These results suggests that BMI plays a role in bleeding events in patients on warfarin.