Recurrent venous thrombosis related to overweight and obesity: results from the MEGA follow-up study.

Essentials Whether excess body weight influences recurrent venous thrombosis (VT) risk is uncertain. We included 3889 VT patients, classified into body mass index (BMI) strata to estimate recurrent VT risk. No evidence of an increased risk for excess body weight was found. Measuring BMI is not a good tool to identify patients at high risk of VT recurrence.

Background Studies on the risk of recurrent venous thrombosis in patients with excess body weight have yielded conflicting results. Objective To estimate whether excess body weight increases the risk of recurrent venous thrombosis. Patients/Methods We included 3889 patients, followed after a first venous thrombosis for a median of 5.6 years. Body mass index (BMI) was calculated as weight in kilograms/height in meters squared, and classified according to three a priori-defined categories (normal weight, overweight, and obesity), as well as by percentiles. Crude incidence rates with 95% confidence intervals (CIs) of recurrent venous thrombosis were estimated as the number of events over the accumulated follow-up time in each BMI category. Cox regression models were used to compare groups, adjusted for age and sex. Results The incidence rate of recurrent venous thrombosis was 3.3 per 100 patient-years. Adjusted hazard ratios of recurrent venous thrombosis in overweight or obese patients in comparison with patients with normal weight were 1.05 (95% CI 0.88-1.27) and 0.94 (95% CI 0.74-1.19), respectively. Stratification by BMI percentile categories yielded similar results. The association between BMI and recurrent venous thrombosis was also absent after stratification by sex, (although a small effect for overweight, but not for obese women, was found), or into those with a first provoked or unprovoked event, or deep vein thrombosis and pulmonary embolism. Conclusions We found no evidence of an association between excess body weight and recurrent venous thrombosis. Measuring BMI is not a useful tool to identify patients at high risk of recurrence.