Obesity measures and risk of venous thromboembolism and myocardial infarction.

Obesity is a risk factor for arterial and venous thromboembolism. However, it is not known whether obesity mediates risk through shared mechanisms. In a population-based cohort, we aimed to compare the impact of obesity measures on risk of venous thromboembolism (VTE) and myocardial infarction (MI), and explore how obesity-related atherosclerotic risk factors influenced these relationships. Measures of body composition including body mass index , waist circumference (WC), hip circumference (HC), waist-hip ratio (WHR) and waist-to-height ratio (WHtR) were registered in 6,708 subjects aged 25-84 years, who participated in the Tromsø Study (1994-1995). Incident VTE- and MI-events were registered until January 1, 2011. There were 288 VTEs and 925 MIs during a median of 15.7 years of follow-up. All obesity measures were related to risk of VTE. In linear models, WC showed the highest risk estimates in both genders. In categorized models (highest versus lowest quintile), WC showed highest risk in men (HR 3.59; 95 % CI 1.82-7.06) and HC in women (HR 2.27; 95 % CI 1.54-4.92). Contrary, WHR and WHtR yielded the highest risk estimates for MI. The HR of MI (highest vs. lowest quintile) for WHR was 2.11 (95 % CI 1.59-2.81) in men and 1.62 (95 % CI 1.13-2.31) in women. The risk estimates for MI were substantially attenuated after adjustment for atherosclerotic risk factors, whereas the estimates for VTE remained unchanged. Our findings suggest that the impact of body fat distribution, and the causal pathway, differs for the association between obesity and arterial and venous thrombosis.