Physical Activity, Energy Intake and the Risk of Incident Kidney Stones

Purpose: Recent data suggest that higher physical activity and lower energy intake may be associated with a lower risk of kidney stones. To our knowledge whether these associations could be reproduced in other study populations after accounting for life-style and dietary factors is not known. Materials and Methods: We analyzed data on 3 large prospective cohorts, including HPFS, and NHS I and II. Information was collected by validated biennial questionnaires. The HR of incident stones in participants in different categories of physical activity and energy intake was assessed by Cox proportion hazards regression adjusted for age, body mass index, race, comorbidity, medication, calcium supplement use, fluid and nutrient intake. Results: Analysis included 215,133 participants. After up to 20 years of followup 5,355 incident cases of kidney stones occurred. On age adjusted analysis higher levels of physical activity were associated with a lower risk of incident kidney stones in women (NHS I and II) but not in men. However, after multivariate adjustment there was no significant association between physical activity and kidney stone risk in HPFS, and NHS I and II (highest vs lowest category HR 1.00, 95% CI 0.87-1.14, p for trend = 0.94, HR 1.01, 95% CI 0.85-1.19, p for trend = 0.88 and HR 1.03, 95% CI 0.90-1.18, p for trend = 0.64, respectively). Energy intake was not associated with stone risk (multivariate adjusted p for trend >= 0.49). Conclusions: In 3 large prospective cohorts there was no independent association between physical activity and energy intake, and the incidence of symptomatic kidney stones.