Body Size Measures and the Risk of Venous Thrombosis: The Longitudinal Investigation of Thromboembolism Etiology (LITE).

Abstract

Background: Obesity is associated with an increased risk of venous thrombosis (VT), however little is known about which components of obesity are important. Proposed hypotheses include an association of adipocyte products with hemostatic imbalance, increased body or leg size impairing venous return, increased inflammation, and differences in venous vessel walls in obese persons. We studied the associations of measures of body size and composition with risk of VT in the LITE study.Methods: The LITE is a prospective study evaluating VT risk factors in 21,680 participants aged 45–100, in the Atherosclerosis Risk in Communities (ARIC) study and the Cardiovascular Health Study (CHS). Baseline body size measures were obtained using standardized methods and bioelectric impedance was used to calculate fat and fat-free mass in CHS participants. 729 participants reporting prebaseline VT or baseline warfarin use were excluded. VT events during 12.6 years of follow up were validated by medical record review and classified as idiopathic or secondary. Body size measures were evaluated as risk factors using Cox proportional hazards models, adjusting for age, sex, race and diabetes status.Results: There were 451 VT events during follow-up (1.8 per 1000 person-years); 182 were idiopathic, 315 were deep vein thrombosis (DVT) and 136 pulmonary embolus (PE) +/− DVT. All body size measures were associated with increased risk of VT (table), with height having the weakest association. Those with severe obesity (body-mass index above 40 kg/m2) were at the highest risk, with a nearly 3-fold increased risk compared to those of normal weight. Both fat and fat-free mass were risk factors.Conclusion: In this prospective study, multiple measures of body size, and measures of body composition including fat and non-fat components, were risk factors for VT. Findings suggest a multicausal pathogenesis for obesity-related thrombosis. Further study is required to determine reasons for the association of body size and composition with VT.Relative Risk of VT by Body Size Categories (Quartiles (Q) Except when Noted; lowest quartile is the reference group)Q1Q2Q3Q4Body-mass index**1.0 (reference)1.3*2.1*2.9*Weight1.0 (ref)1.21.5*2.5*Height1.0 (ref)1.11.21.4*Waist-hip ratio1.0 (ref)1.31.5*1.6*Waist Circumference1.0 (ref)1.21.32.1*Hip Circumference1.0 (ref)1.3*1.5*2.2*Calf Circumference1.0 (ref)1.32.0*2.3*Fat-Free Mass1.0 (ref)1.21.41.9*Fat Mass1.0 (ref)1.10.81.7** P <0.05; ** categories are <25, 25–20, 30–40, >40 kg/m2