Bariatric Surgery and the Long-Term Risk of Venous Thromboembolism: A Population-Based Cohort Study.

PURPOSE: Bariatric surgery is associated with a greater venous thromboembolism (VTE) risk in the weeks following surgery, but the long-term risk of VTE is incompletely characterized. We evaluated bariatric surgery in relation to long-term VTE risk.

MATERIALS AND METHODS: This population-based retrospective matched cohort study within three United States-based integrated health care systems included adults with body mass index (BMI) ≥ 35 kg/m2 who underwent bariatric surgery between January 2005 and September 2015 (n = 30,171), matched to nonsurgical patients on site, age, sex, BMI, diabetes, insulin use, race/ethnicity, comorbidity score, and health care utilization (n = 218,961). Follow-up for incident VTE ended September 2015 (median 9.3, max 10.7 years).

RESULTS: Our population included 30,171 bariatric surgery patients and 218,961 controls; we identified 4068 VTE events. At 30 days post-index date, bariatric surgery was associated with a fivefold greater VTE risk (HRadj  = 5.01; 95% CI = 4.14, 6.05) and a nearly fourfold greater PE risk (HRadj  = 3.93; 95% CI = 2.87, 5.38) than no bariatric surgery. At 1 year post-index date, bariatric surgery was associated with a 48% lower VTE risk and a 70% lower PE risk (HRadj  = 0.52; 95% CI = 0.41, 0.66 and HRadj  = 0.30; 95% CI = 0.21, 0.44, respectively). At 5 years post-index date, lower VTE risks persisted, with bariatric surgery associated with a 41% lower VTE risk and a 55% lower PE risk (HRadj  = 0.59; 95% CI = 0.48, 0.73 and HRadj  = 0.45; 95% CI = 0.32, 0.64, respectively).

CONCLUSION: Although in the short-term bariatric surgery is associated with a greater VTE risk, in the long-term, it is associated with a substantially lower risk.