Assessment of the Relationship between Body Mass Index and Incidence of Venous Thromboembolism in Hospitalized Overweight and Obese Patients.

STUDY OBJECTIVE: To assess whether a positive linear association exists between body mass index (BMI) and incidence of venous thromboembolism (VTE) in overweight and obese hospitalized patients.

DESIGN: Single-center retrospective observational cohort study.

SETTING: Large academic tertiary care medical center.

PATIENTS: A total of 1452 adults hospitalized between January 1, 2013, and December 31, 2014, who weighed more than 100 kg and had a BMI of 25 kg/m2 or greater on admission, and received heparin subcutaneously for VTE prophylaxis. Patients were categorized into four subgroups based on World Health Organization BMI classification: overweight (141 patients), obese class I (305 patients), obese class II (324 patients), and obese class III (682 patients).

MEASUREMENTS AND MAIN RESULTS: The primary outcome was occurrence of VTE in each subgroup; all-cause mortality and length of hospital stay were secondary outcomes. A linear trend test did not show an association between occurrence of VTE and BMI of 25 kg/m2 or greater. VTE occurred in 7 (5%) of 141 patients in the overweight group, 5 (2%) of 305 in the obese class I group, 8 (3%) of 324 in the class II group, and 18 (3%) of 682 in the class III group (p=0.573). In addition, no linear association was noted between all-cause mortality or length of hospital stay and BMI of 25 kg/m2 or greater. Overall mortality was 10% (146/1452 patients). Ten deaths (7%) occurred in the overweight group, 45 (15%) in the obese class I group, 38 (12%) in the obese class II group, and 53 (8%) in the obese class III group (p=0.067). The median length of hospital stay was 5 days (interquartile range 3-9, p=0.122) for all patients.

CONCLUSION: In overweight and obese hospitalized patients who weighed more than 100 kg and had a BMI of 25 kg/m2 or greater, the incidence of VTE did not increase incrementally with increasing severity of obesity.