ABSTRACT
Objective: To evaluate the associations of body mass index (BMI) and waist circumference with hospitalization risk of kidney stones in Chinese adults. Methods: This study used long-term follow-up data from China Kadoorie Biobank. After excluding participants with chronic kidney disease, cancer, and extreme BMI or waist circumference values at baseline, 502 096 participants were included in the present analysis. Cox proportional hazards regression models were used to estimate the associations of BMI and waist circumference with hospitalization risk of kidney stones. Results: During an average follow-up period of (10.7±2.2) years, 12 396 participants were hospitalized for the first time with kidney stones. Using the participants with BMI (kg/m2) of 20.5-22.4 as reference, the multivariable-adjusted HR (95%CI) for those with BMI of <18.5, 18.5-20.4, 22.5-23.9, 24.0-25.9, 26.0-27.9, 28.0-29.9, and ≥30.0 were 0.96 (0.87-1.05), 0.94 (0.88-1.00), 1.11 (1.05-1.17), 1.25 (1.18-1.32), 1.29 (1.21-1.37), 1.39 (1.28-1.50), and 1.54 (1.40-1.71), respectively. For every 1 kg/m2 increase in BMI, the HR of kidney stones hospitalization increased by 4% (HR=1.04, 95%CI: 1.04-1.05). Using the participants with waist circumference (cm) of 75.0-79.9 as reference, the multivariable-adjusted HR (95%CI) for those with waist circumference of <65.0, 65.0-69.9, 70.0-74.9, 80.0-84.9, 85.0-89.9, 90.0-94.9, and ≥95.0 were 0.82 (0.74-0.91), 0.85 (0.80-0.92), 0.95 (0.89-1.00), 1.16 (1.09-1.22), 1.22 (1.15-1.30), 1.28 (1.19-1.38), and 1.46 (1.35-1.58), respectively. For every 5 cm increase in waist circumference, the HR of kidney stones hospitalization increased by 9% (HR=1.09, 95%CI: 1.08-1.10). After mutually adjusting for BMI and waist circumference in the above models, the association between BMI and hospitalization risk of kidney stones disappeared. In contrast, the association between waist circumference and hospitalization risk of kidney stones remained unchanged. Conclusions: BMI and waist circumference were positively associated with hospitalization risk of kidney stones. The increased waist circumference was an independent risk factor for kidney stones among Chinese adults.