Underweight status and development of end-stage kidney disease: A nationwide population-based study.

Background: Underweight status increases the risk of cardiovascular disease and mortality in the general population. However, whether underweight status is associated with an increased risk of developing end-stage kidney disease is unknown.

Methods: A total of 9 845 420 participants aged ≥20 years who underwent health checkups were identified from the Korean National Health Insurance Service database and analysed. Individuals with underweight (body mass index [BMI] < 18.5 kg/m ) and obesity (BMI ≥ 25 kg/m ) were categorized according to the World Health Organization recommendations for Asian populations.

Results: During a mean follow-up period of 9.2 ± 1.1 years, 26 406 participants were diagnosed with end-stage kidney disease. After fully adjusting for other potential predictors, the moderate to severe underweight group (<17 kg/m ) had a significantly higher risk of end-stage kidney disease than that of the reference (normal) weight group (adjusted hazard ratio, 1.563; 95% confidence interval, 1.337-1.828), and competing risk analysis to address the competing risk of death also showed the similar results (adjusted hazard ratio, 1.228; 95% confidence interval, 1.042-1.448). Compared with that of the reference BMI group (24-25 kg/m ), the adjusted hazard ratios for end-stage kidney disease increased as the BMI decreased by 1 kg/m . In the sensitivity analysis, sustained underweight status or progression to underweight status over two repeated health checkups, when compared with normal weight status, had a higher hazard ratio for end-stage kidney disease.

Conclusions: Underweight status is associated with an increased risk of end-stage kidney disease, and this association gradually strengthens as BMI decreases.