The Prognostic Significance of Body Mass Index and Metabolic Parameter Variabilities in Predialysis CKD: A Nationwide Observational Cohort Study

Significance statement The prognostic significance of variabilities in body mass index (BMI) or metabolic parameters in patients with CKD is uncertain. In this observational cohort study of 84,636 patients with predialysis CKD in South Korea, the authors analyzed the association between variability of BMI or various metabolic parameters and risks of all-cause mortality and incident myocardial infarction, stroke, and requirement for KRT. They found that elevated variability in BMI or certain metabolic parameters was associated with higher risks of adverse outcomes, independent of baseline metabolic status. These findings may encourage clinicians in the nephrology field to carefully assess not only baseline BMI or metabolic status in patients with CKD, but also the fluctuating status of metabolic parameters, due to their potential prognostic significance in such patients. Background The association between variabilities in body mass index (BMI) or metabolic parameters and prognosis of patients with CKD has rarely been studied. Methods In this retrospective observational study on the basis of South Korea’s national health screening database, we identified individuals who received ≥3 health screenings, including those with persistent predialysis CKD (eGFR <60 ml/min per 1.73 m 2 or dipstick albuminuria ≥1). The study exposure was variability in BMI or metabolic parameters until baseline assessment, calculated as the variation independent of the mean and stratified into quartiles (with Q4 the highest quartile and Q1 the lowest). We used Cox regression adjusted for various clinical characteristics to analyze risks of all-cause mortality and incident myocardial infarction, stroke, and KRT. Results The study included 84,636 patients with predialysis CKD. Comparing Q4 versus Q1, higher BMI variability was significantly associated with higher risks of all-cause mortality (hazard ratio [HR], 1.66; 95% confidence interval [95% CI], 1.53 to 1.81), P [for trend] <0.001), KRT (HR, 1.20; 95% CI, 1.09 to 1.33; P <0.001), myocardial infarction (HR, 1.19; 95% CI, 1.05 to 1.36, P =0.003), and stroke (HR, 1.19; 95% CI, 1.07 to 1.33, P =0.01). The results were similar in the subgroups divided according to positive or negative trends in BMI during the exposure assessment period. Variabilities in certain metabolic syndrome components ( e.g ., fasting blood glucose) also were significantly associated with prognosis of patients with predialysis CKD. Those with a higher number of metabolic syndrome components with high variability had a worse prognosis. Conclusions Higher variabilities in BMI and certain metabolic syndrome components are significantly associated with a worse prognosis in patients with predialysis CKD.