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SEX DIFFERENCES IN THE RISK OF KIDNEY STONES Free

Kidney stone disease is a highly prevalent condition. Men are at higher risk of developing stones compared with women, however recent data suggest a changing epidemiology with women being relatively more affected than in the past. The reasons for such differences and changes over time are not clear.

We analyzed the association between sex and the first symptomatic incident kidney stone using data from three large, longitudinal cohorts. Incidence rates for men and women overall and across categories of age and calendar time were computed and hazard ratios (HRs) and 95% confidence intervals (CIs) generated with age-adjusted Cox proportional hazards regression models. Mediation analysis was performed in order to estimate the amount of excess risk for men explained by established risk factors, including BMI, waist circumference, history of high blood pressure, history of diabetes, use of thiazides, dietary intakes of animal protein, caffeine, fructose, potassium, sodium, oxalate, phytate, dietary and supplemental intakes of calcium, vitamin C and vitamin D, sugar-sweetened beverages and total fluid intake.

The analysis included data from 268,616 participants, contributing 5,876,205 person-years of follow-up, during which 10,303 incident stone events were confirmed. The overall incidence rate of kidney stones was 271 and 158 per 100,000 person-years for men and women, respectively. The age-adjusted HR for men compared with women was 2.32 (95% CI 2.20, 2.45). About 18% of the difference in rates was explained by the risk factors included in the analysis. The risk of stones was consistently higher across categories of age among men compared with women. With regard to calendar time, the risk remained higher among men, but tended to decrease over time while it increased among women, resulting in a relative risk reduction of 38% for after 2009 compared with before 1990.

The risk of kidney stones is higher among men compared with women. This difference is only partly explained by modifiable risk factors.