Association between body mass index and survival after hematopoietic stem cell transplantation

Background/Aims: The unclear relationship between body mass index (BMI) and post-hematopoietic stem cell transplantation (HSCT) mortality was investigated, including the impact of metabolic diseases. Methods: This retrospective study conducted at a Korean tertiary hospital (2009–2021) included patients who underwent HSCT. Patients were categorized as underweight (BMI < 18.5 kg/m², n = 106), normal (BMI 18.5–22.9 kg/m², n = 1,345), overweight (BMI 23.0–24.9 kg/m², n = 980), or obese (BMI ≥ 25.0 kg/m², n = 1,471). Diabetes mellitus (DM), hypertension, and dyslipidemia were identified by disease codes or medication prescriptions. A Cox proportional hazards model was used to analyze mortality risks. Results: Over 108 months, 29.8% (1,164/3,902) of the participants died. Patients with underweight had significantly higher mortality (adjusted HR 1.76, 95% CI 1.29–2.40, p < 0.001) than in those with normal BMI. Patients with overweight and obesity did not show increased mortality. Post-HSCT, DM significantly raised mortality risk (HR 3.36, 95% CI 2.86–3.94, p < 0.001), whereas newly diagnosed dyslipidemia was associated with lower mortality (HR 0.27, 95% CI 0.23–0.33, p < 0.001). Post-transplant hypertension had no significant impact on mortality (HR 1.10, 95% CI 0.95–1.28, p = 0.184). Conclusions: Post-HSCT, obesity is not a prognostic factor for poor survival; however, certain metabolic diseases have diverse effects on mortality.