Association between body mass index, waist circumference, and relative fat mass with the risk of first unprovoked venous thromboembolism

Background and aims: Obesity defined by body mass index (BMI) is independently associated with venous thromboembolism (VTE). Abdominal obesity, defined by waist circumference, is a predictor of cardiovascular events. Recently, relative fat mass (RFM) was proposed as a marker of cardiovascular risk. We assessed the role of three different measures of obesity to predict unprovoked VTE in a longitudinal study. Methods and results: Moli-sani is a prospective cohort study carried out in the general population of the Molise region, Italy. A total of 23,538 individuals (48% men, age 55.4 years) enrolled between 2005 and 2010 were eligible. Patients on anticoagulant treatment were excluded. BMI ≥30 kg/m2 defined obesity, waist circumference >102 cm for men or 88 cm for women defined abdominal obesity, tertiles of RFM were compared. The long-term incidence of first unprovoked VTE during follow-up was assessed. Overall, 29.6% individuals were obese and 44.2% had abdominal obesity. A total of 66 first unprovoked VTE events were diagnosed during a median follow-up of 8.2 years. After multivariable Cox regression analysis, the risk of unprovoked VTE was significantly higher in obese participants (HR 1.89, 95% CI 1.16–3.07) than in participants with BMI <30; in subjects with abdominal obesity than with normal waist circumference (HR 2.19, 1.26–3.81); and in subjects with third vs first RFM tertile index (HR 2.46, 1.15–5.28). The areas under the curves for the models including the three obesity indexes were comparable. Conclusions: Three indexes of obesity based on BMI, waist circumference or RFM similarly predict first occurrence of unprovoked VTE.