Nephrolithiasis Among Middle Aged and Elderly Urban Chinese: A Report from Prospective Cohort Studies in Shanghai

Kidney stone risk factors are understudied among Asians. Our study objective was to investigate associations of obesity and other chronic diseases with incident kidney stones among the urban Chinese. Included in this study are two prospective cohorts: the Shanghai Women's Health Study (N = 69,166) and Shanghai Men's Health Study (N = 58,054). Incident kidney stones were determined by self-report in 2004 and 2008. Cox regression models were used to evaluate the associations of study variables with stone risk with adjustment of demographics, medical history, and dietary intakes. There were 2653 incident stones over 1,007,958 person-years of follow-up. Overall incidence rates (per 1000 person-years, 95% confidence interval [CI]) were 2.10 (1.99, 2.21) among women and 3.80 (3.59, 4.02) among men. Higher body mass index (BMI) was associated with risk (BMI ≥25 vs 18.5-24.9 kg/m , women: hazard ratio [HR] = 1.14 [95% CI 1.01, 1.28]; men: HR = 1.17 [1.03, 1.32]). High waist-hip ratio (≥0.80 and ≥0.90 for women and men, respectively) was associated with risk (HR 1.13, 95% CI 1.01, 1.27 for women; HR 1.19, 95% CI 1.05, 1.35 for men). Coronary heart disease or stroke history was associated with risk in women only (HR 1.31, 95% CI 1.10, 1.56). Hypertension history was associated with risk in men only (HR 1.27, 95% CI 1.11, 1.45). No significant association with diabetes mellitus was observed. Among the Chinese, kidney stone incidence in men is almost twice that of women. Obesity is a shared risk factor. Hypertension history is associated with risk in men, whereas history of coronary heart disease or stroke is associated with risk in women.