Abstract. Menopause is associated with increased urinary calcium excretion, which could increase the risk for the development of calcium-containing kidney stones. However, it is unknown whether menopause and postmenopausal hormone (PMH) use are independent risk factors for incident kidney stone disease in women. Data from 91,731 female Nurses' Health Study participants who provided information on diet, menopause status, and kidney stone disease were used to examine the independent association between menopause and PMH use and risk of incident kidney stones. No association was found between menopause and incident kidney stones in age-adjusted (relative risk [RR], 1.07; 95% CI, 0.85 to 1.34) or multivariate models (RR, 1.12; 95% CI, 0.89 to 1.41). However, when the association between the type of menopause and risk of incident kidney stones was examined, surgical menopause was associated with an increased risk in both the ageadjusted (RR, 1.37; 95% CI, 1.05 to 1.77) and multivariate models (RR, 1.39; 95% CI, 1.07 to 1.81), whereas natural menopause was not. Compared with never-use, past or current PMH use (including duration of PMH use) was not associated with incident kidney stones among postmenopausal women. In conclusion, no association was found between menopause and PMH use and incident kidney stones. Surgical menopause, however, may be associated with an increased risk.Approximately 5% of all women living in the United States will experience the passage of a kidney stone before the age of 70 yr (1). The passage of a kidney stone is very painful, and the costs incurred due to treatment, morbidity, and time lost from work are substantial (2). Increased urinary calcium excretion is an important risk factor for the development of calcium-containing kidney stones (3), which account for over 80% of all kidney stones in the United States (4). Compared with urinary calcium concentrations Ͻ 75 mg/L, the relative risk for kidney stones increased from twofold in subjects with urinary calcium 100 to 149 mg/L to over fourfold in subjects with Ն 200 mg/L (5). Thus, even moderate increases in urinary calcium excretion may substantially increase the risk for stone formation.Menopause is associated with an increase in urinary calcium excretion (6,7), which may increase the risk for calciumcontaining stone formation. In subjects matched for serum total and ionized calcium levels, urinary calcium excretion was 50% higher (P Ͻ 0.001) in postmenopausal women compared with premenopausal women (6). Thus, the onset of menopause may increase urinary calcium excretion and the risk for kidney stone formation. In contrast, postmenopausal hormone (PMH) use has been shown to decrease fasting urinary calcium by 50% compared with baseline in postmenopausal women (8). It is currently not known whether menopause and PMH use are independent risk factors for kidney stone formation in women. The aim of this study was to prospectively study the independent association among menopause, PMH use, and risk of incident kidney stones in women.
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