Dietary and Lifestyle Risk Factors Associated with Incident Kidney Stones in Men and Women

Purpose: Several dietary and lifestyle factors are associated with a higher risk of kidney stones. We estimated the population attributable fraction and the number needed to prevent for modifiable risk factors, including body mass index, fluid intake, DASH (Dietary Approaches to Stop Hypertension) style diet, dietary calcium intake and sugar sweetened beverage intake. Materials and Methods: We used data on the HPFS (Health Professionals Follow-Up Study) cohort and the NHS (Nurses' Health Study) I and II cohorts. Information was obtained from validated questionnaires. Poisson regression models adjusted for potential confounders were used to estimate the association of each risk factor with the development of incident kidney stones and calculate the population attributable fraction and the number needed to prevent. Results: The study included 192,126 participants who contributed a total of 3,259,313 person-years of followup, during which an incident kidney stone developed in 6,449 participants. All modifiable risk factors were independently associated with incident stones in each cohort. The population attributable fraction ranged from 4.4% for a higher intake of sugar sweetened beverages to 26.0% for a lower fluid intake. The population attributable fraction for all 5 risk factors combined was 57.0% in HPFS, 55.2% in NHS I and 55.1% in NHS II. The number needed to prevent during 10 years ranged from 67 for lower fluid intake to 556 for lower dietary calcium intake. Conclusions: Five modifiable risk factors accounted for more than 50% of incident kidney stones in 3 large prospective cohorts. Assuming a causal relation, our estimates suggest that preventive measures aimed at reducing those factors could substantially decrease the burden of kidney stones in the general population.