The impact of body mass index on mortality according to age in hemodialysis patients: an analysis of the Korean Renal Data System.

Abstract

The impact of age on the relationship between body mass index (BMI) and all-cause mortality in hemodialysis (HD) patients is not clearly understood. We analyzed the association between BMI and all-cause mortality, stratified by age, in patients undergoing HD using data from the Korean Renal Data System (KORDS). We analyzed 66,129 HD patients from the 2023 KORDS database, with data collected between 2001 and 2022. Patients were grouped by age: <65 years ("young" group, n = 24,589), 65-74 years ("younger-old" group, n = 17,732), and ≥75 years ("older-old" group, n = 23,808). Patients were further stratified into BMI quartiles. Kaplan-Meier curves and event time ratio for the relative change in the survival time were calculated. During the follow-up period, 14,360 (21.7%) of the patients died, with a median follow-up of 3.4 years. Kaplan-Meier curves revealed poorer outcomes in lower BMI quartiles across all age groups. The lowest BMI quartile was significantly associated with a shorter survival time compared to the highest BMI quartile, with a 15% reduction in the young group (p = 0.001) and a 12% reduction in the older-old group (p = 0.002). Predicted survival time increases with rising BMI in the young group, but the rate of increase slows in the younger-old group and plateaus in the older-old group after around a BMI of 25 kg/m2. The decline in survival time with age was more pronounced in the 7-year survival than the 2-year survival. Lower BMI is associated with higher all-cause mortality in HD patients, with a more pronounced impact in younger patients.