Context Larger body size may result in increased urinary excretion of calcium, oxalate, and uric acid, thereby increasing the risk for calcium-containing kidney stones. It is unclear if obesity increases the risk of stone formation, and it is not known if weight gain influences risk.Objective To determine if weight, weight gain, body mass index (BMI), and waist circumference are associated with kidney stone formation. Design, Setting, and ParticipantsA prospective study of 3 large cohorts: the Health Professionals Follow-up Study (N=45988 men; age range at baseline, 40-75 years), the Nurses' Health Study I (N=93758 older women; age range at baseline, 34-59 years), and the Nurses' Health Study II (N=101877 younger women; age range at baseline, 27-44 years).Main Outcome Measures Incidence of symptomatic kidney stones. ResultsWe documented 4827 incident kidney stones over a combined 46 years of follow-up. After adjusting for age, dietary factors, fluid intake, and thiazide use, the relative risk (RR) for stone formation in men weighing more than 220 lb (100.0 kg) vs men less than 150 lb (68.2 kg) was 1.44 (95% confidence interval [CI], 1.11-1.86; P=.002 for trend). In older and younger women, RRs for these weight categories were 1.89 (95% CI, 1.52-2.36; PϽ.001 for trend) and 1.92 (95% CI, 1.59-2.31; PϽ.001 for trend), respectively. The RR in men who gained more than 35 lb (15.9 kg) since age 21 years vs men whose weight did not change was 1.39 (95% CI, 1.14-1.70; P=.001 for trend). Corresponding RRs for the same categories of weight gain since age 18 years in older and younger women were 1.70 (95% CI, 1.40-2.05; PϽ.001 for trend) and 1.82 (95% CI, 1.50-2.21; PϽ.001 for trend). Body mass index was associated with the risk of kidney stone formation: the RR for men with a BMI of 30 or greater vs those with a BMI of 21 to 22.9 was 1.33 (95% CI, 1.08-1.63; PϽ.001 for trend). Corresponding RRs for the same categories of BMI in older and younger women were 1.90 (95% CI, 1.61-2.25; PϽ.001 for trend) and 2.09 (95% CI, 1.77-2.48; PϽ.001 for trend). Waist circumference was also positively associated with risk in men (P=.002 for trend) and in older and younger women (PϽ.001 for trend for both). ConclusionsObesity and weight gain increase the risk of kidney stone formation. The magnitude of the increased risk may be greater in women than in men.

Abstract. Diet plays an important role in the pathogenesis of kidney stones. Because the metabolism of many dietary factors, such as calcium, may change with age, the relation between diet and kidney stones may be different in older adults. Uncertainty also remains about the association between many dietary factors, such as vitamin C, magnesium, and animal protein, and the risk of kidney stone formation. To examine the association between dietary factors and the risk of incident, symptomatic kidney stones in men and to determine whether these associations vary with age, a prospective cohort study was conducted of 45,619 men without a history of nephrolithiasis. Self-administered food frequency questionnaires were used to assess diet every 4 yr. A total of 1473 incident symptomatic kidney stones were documented during 477,700 person-years of follow-up. For men aged Ͻ60 yr, the multivariate relative risk (RR) for stone formation in the highest quintile of dietary calcium as compared with the lowest quintile was 0.69 (95% confidence interval [CI], 0.56 to 0.87; P ϭ 0.01 for trend). By contrast, there was no association between dietary calcium and stone formation in men aged 60 yr or older. The multivariate RR for men who consumed 1000 mg or greater of vitamin C per day compared with those who consumed less than the recommended dietary allowance of 90 mg/d was 1.41 (95% CI, 1.11 to 1.80; P ϭ 0.01 for trend). Other dietary factors showed the following multivariate RR among men in the highest quintile of intake compared with those in the lowest: magnesium, 0.71 (95% CI, 0.56 to 0.89; P ϭ 0.01 for trend); potassium, 0.54 (95% CI, 0.42 to 0.68; P Ͻ 0.001 for trend); and fluid, 0.71 (95% CI, 0.59 to 0.85; P Ͻ 0.001 for trend). Animal protein was associated with risk only in men with a body mass index Ͻ25 kg/m 2 (RR, 1.38; 95% CI, 1.05 to 1.81; P ϭ 0.03 for trend). Sodium, phosphorus, sucrose, phytate, vitamin B 6 , vitamin D, and supplemental calcium were not independently associated with risk. In conclusion, the association between calcium intake and kidney stone formation varies with age. Magnesium intake decreases and total vitamin C intake seems to increase the risk of symptomatic nephrolithiasis. Because age and body size affect the relation between diet and kidney stones, dietary recommendations for stone prevention should be tailored to the individual patient.Diet plays an important role in the pathogenesis of kidney stones (1), but little is known about the effect of aging on the association between specific dietary factors and nephrolithiasis. In the past, prospective studies that evaluated dietary influences on kidney stone formation included only small numbers of older participants. The first observational studies to demonstrate an inverse association between dietary calcium and incident kidney stones analyzed stone formers who as a group were predominately younger than 60 yr (2,3). The mean age of subjects in the controlled, randomized trial that supported the results of these studies was 45 yr (4).The relati...

DM is a risk factor for the development of kidney stones. Additional studies are needed to determine if the increased risk of DM in stone formers is due to subclinical insulin resistance.