An inverse association between BMI and VTE occurrence was observed among at-risk inpatients, most pronounced in older, female, and surgical subgroups, while obesity remained a risk factor in medical patients and, among surgical patients who developed VTE, was paradoxically associated with lower mortality.
About 1.8% of 3,199,526 at-risk inpatients in a nationwide hospital-based cohort developed VTE during hospitalization.
Overweight and obesity were associated with a lower risk of VTE occurrence compared with normal weight after adjustment.
The protective association of overweight/obesity with VTE occurrence was more pronounced in patients aged ≥65 years, female patients, and surgical patients.
In internal medicine patients, obesity was associated with a higher risk of VTE occurrence, in contrast to the overall inverse association.
Overweight/obesity was not significantly associated with post-VTE in-hospital mortality overall.
Among surgical patients who developed VTE, obesity was associated with lower post-VTE mortality.
This study looked at more than 3.1 million hospitalized patients in China who were at potential risk of blood clots in the veins (venous thromboembolism, or VTE). About 1.8% developed a clot during their hospital stay. Surprisingly, patients who were overweight or had obesity were less likely to be diagnosed with VTE than patients of normal weight, with about 18% and 22% lower odds respectively after accounting for other factors. The pattern was not the same for everyone. The lower risk with higher BMI was stronger in people aged 65 and older, women, and surgical patients. In patients on internal medicine services, however, obesity was linked to a somewhat higher risk of VTE. Among patients who developed VTE, BMI was generally not linked to dying in the hospital, though in surgical patients obesity was associated with lower mortality. These findings suggest the relationship between body weight and blood clots in hospitalized patients is complex and differs by patient group and type of care. This is an observational study, so it cannot show that higher BMI causes lower risk; the results may reflect how patients are assessed, treated, or diagnosed. The research suggests that risk assessment may need to consider the clinical setting rather than relying on BMI alone.
Li Y, Xia L, Li H, Wang D, Zhang Z, Fan G, et al.. (2026). Paradoxical Association of Body Mass Index With Occurrence and Mortality of Venous Thromboembolism in Hospitalized Patients: A National Hospital-Based Cohort Analysis.. Journal of the American Heart Association. https://doi.org/10.1161/JAHA.125.045575