Body mass index and weight change are associated with mortality in chronic kidney disease: A retrospective cohort study using a Japanese medical claims database

This study aimed to investigate body mass index (BMI) and rate of weight change associated with adverse outcomes in Asian patients with chronic kidney disease.A retrospective cohort study was performed between April 2014 and June 2022 using the administrative claims database compiled by the Japan Medical Data Center. Patients were defined as individuals with comorbidities with chronic kidney disease stages 3 to 5 on admission and were aged ≥40 y with BMI at admission and BMI information from a previous admission 3 to 12 mo earlier. Restricted cubic spline analysis and thin-plate smoothed spline analysis were performed.A total of 10 802 individuals were analyzed. The mean age was 74.6 ± 11.3 y, number of men was 7175 (66.4%), and 2115 (19.6%) deaths were recorded. Smoothed splines for BMI found that low BMI was associated with high hazard ratio (HR) (BMI = 18.5 kg/m2; HR = 1.3 [1.2-1.4]). Smoothed splines of weight change found higher HR with increasing rate of weight change for both weight gain and loss (weight change rate = -10%; HR = 1.4 [1.3-1.5]; weight change rate = 10%; HR = 1.2 [1.1-1.3]). In thin-plate smoothed spline analysis, the U-curve had a higher odds ratio as BMI decreased in patients with or without dialysis and as the degree of weight change increased.We found trends in BMI and rate of weight change associated with mortality in Asian patients with chronic kidney disease.