Impact of Annual Dry Weight Changes on Mortality and Cardiovascular Outcomes in Patients Undergoing Haemodialysis

Background: While obesity confers a survival advantage, weight loss adversely affects the survival of patients undergoing haemodialysis. However, given the limited information regarding its long-term effects on mortality and cardiovascular events, the health benefits of weight gain remain uncertain, particularly in Asian patients undergoing haemodialysis. Methods: In a prospective multicentre cohort of patients undergoing haemodialysis in South Korea, patients whose dry weight was recorded at baseline and after 1 year were analysed. Patients were stratified into five groups according to annual dry weight change: stable (−2.0% to 1.9%, n = 245), mild (2.0% to 6.9%, n = 92) and moderate (≥ 7.0%, n = 20) dry weight gain and mild (−5.0% to −2.1%, n = 91) and moderate (< −5.0%, n = 77) dry weight loss. The associations of annual dry weight change with physical function and health-related quality of life were examined using cross-sectional analysis. The impact of annual dry weight changes on all-cause mortality and a composite of major adverse cardiovascular events (MACEs), defined as myocardial infarction, unstable angina, ischaemic stroke and peripheral artery disease requiring revascularization, was assessed in a longitudinal cohort of 525 individuals. Results: In cross-sectional analysis, patients with diminished physical ability had a higher frequency of dry weight fluctuations. In longitudinal analysis, the mean age of the study participants was 59.9 years, and 62.3% were men. During a median follow-up of 3.1 years, death and MACE occurred in 105 (20.0%) and 31 (5.9%) patients, respectively. The risk of all-cause mortality was higher in patients with moderate dry weight gain or loss than in those with stable dry weight (adjusted hazard ratio [aHR] for moderate weight gain, 2.22; 95% confidence interval [CI], 0.96–5.13; p = 0.06; and aHR for moderate weight loss, 1.78; 95% CI, 1.07–2.95; p = 0.03). The risk of MACE was significantly higher in patients with weight gain (including mild and moderate) than in those with a stable dry weight (aHR, 3.02; 95% CI, 1.32–6.88; p = 0.009). Specifically, the increased risk of all-cause mortality attributable to moderate dry weight gain was limited to patients with obesity, whereas that for moderate dry weight loss was limited to patients with a normal body mass index. Conclusion: Moderate weight gain and loss were differentially associated with lower survival among patients undergoing haemodialysis, with the former in patients with obesity and the latter in normal-weight patients. Particularly, dry weight gain increased the risk of cardiovascular events.