The Obesity Paradox Reconsidered: Evidence from a Multicenter Romanian Hemodialysis Cohort.

Background and Objectives: The obesity paradox in maintenance hemodialysis (MHD) patients (better survival of obese as compared to non-obese patients in MHD) remains controversial, with many published papers supporting the idea that higher BMI is protective. Data from Eastern Europe, in particular from the elderly population on hemodialysis, are limited. The aim of this study was to describe the distribution of body weight status and cardiometabolic comorbidities and to evaluate the association of BMI categories with all-cause mortality in a multi-center Romanian hemodialysis cohort. Materials and Methods: We conducted a retrospective cohort study of 679 patients with end-stage kidney disease (ESKD) undergoing maintenance haemodialysis in eight Romanian centers. All patients received thrice-weekly treatments (≥4 h/session) using high-flux dialysers. Baseline demographic, clinical, laboratory, and echocardiographic data were extracted from dialysis records. Survival across BMI groups was assessed using Kaplan-Meier curves and the log-rank test. Cox proportional hazards models were used to estimate hazard ratios (HRs) for all-cause mortality, with normal weight as the reference category. Multivariable models incorporated progressive adjustment for age, sex, dialysis vintage, diabetes, major cardiovascular comorbidities, and ESKD-related factors, including anemia parameters and CKD-mineral and bone disorder (CKD-MBD) markers. Results: A total of 679 haemodialysis patients were included (mean age 57.2 ± 12.9 years; 59.1% male); 52.7% were normal weight, 28.9% overweight, and 18.4% obese. During follow-up, 360 patients (53.0%) died, with similar crude mortality across BMI groups (normal weight 51.7%, overweight 55.1%, obese 53.6%; p > 0.05). In univariate Cox analyses, older age, obesity, hypoalbuminaemia, elevated CRP, hyperphosphataemia, peripheral and cerebrovascular disease, diabetes, low dialysis adequacy (eKt/V < 1.2), and lower ultrafiltration were associated with higher mortality, whereas preserved LVEF (≥50%) was protective. In multivariable analyses, independent predictors of mortality included older age (HR 1.042 per year, p < 0.001), obesity (HR 1.411, p = 0.045), elevated CRP (HR 1.781, p < 0.001), diabetes (HR 1.775, p < 0.001), inadequate dialysis dose (eKt/V < 1.2; HR 1.343, p = 0.029), and preserved LVEF remained protective (HR 0.665, p = 0.013). The Kaplan-Meier analysis showed significantly lower survival with increasing BMI: median survival was 7.56 years in normal-weight patients, 4.56 years in overweight patients, and 3.92 years in obese individuals (log-rank p < 0.05). Conclusions: In this Romanian cohort of multicenter hemodialysis patients, obesity as measured by BMI was associated with an increased incidence of all-cause mortality, while overweight did not confer a clear survival advantage over normal weight. These findings call into question the classic hemodialysis obesity paradox and support a more cautious interpretation of the increased BMI.