Obesity measurement methods estimated mortality risk in patients undergoing hemodialysis: a systematic review and meta-analysis

Purpose: The impact of obesity on mortality risk in patients undergoing hemodialysis (HD) remains uncertain due to conflicting findings across obesity measurement methods. This study aimed to assess the obesity measurements influence mortality risk in HD populations. Methods: Systematic review and meta-analysis were conducted following PRISMA guidelines, registered on PROSPERO (CRD42023429943). Relevant observational studies analyzing mortality risk using obesity measurements in adult HD patients up to March 27, 2023 were included from multiple databases, including EMBASE, MEDLINE (OVID), and CINAHL (EBSCO). Pooled analyses with a random-effects model were performed using RevMan 5.4. Results: Twenty-three studies involving 381,580 subjects were reviewed. A meta-analysis of 15 studies in event-based analysis showed contrasting results between anthropometry and body composition analysis in predicting all-cause mortality. Obese patients indicated by body mass index (BMI) had a lower mortality risk than non-obese patients (RR = 0.73, 95% CI: 0.70-0.76, p < 0.001). In contrast, abdominal obesity measured by waist circumference (WC) or waist-to-hip ratio (WHR) increased mortality risk (RR = 1.35, 95% CI: 1.01-1.80, p = 0.04). Studies using bioelectrical impedance analysis (BIA) demonstrated an increased mortality risk for obese patients (RR = 1.22, 95% CI: 1.05-1.41, p = 0.009). Conclusions: Obese patients undergoing HD exhibit different mortality risks depending on the methods of obesity measurement. The observed 'obesity paradox' in patients on HD, where lower mortality is seen with obesity measured by BMI, may reflect BMI's limitations in differentiating fat mass. More studies with other anthropometry and body composition analysis are needed to clarify this phenomenon.