Redefining the Stone Belt: Precipitation Is Associated with Increased Risk of Urinary Stone Disease

Objectives: The American Southeast has been labeled the "Stone Belt" due to its relatively high burden of urinary stone disease, presumed to be related to its higher temperatures. However, other regions with high temperatures (e.g., the Southwest) do not have the same disease prevalence as the southeast. We seek to explore the association of stone disease to other climate-associated factors beyond temperature, including precipitation and temperature variation. Methods: We identified all patients who underwent a surgical procedure for urinary stone disease from the California Office of Statewide Health Planning and Development (OSHPD) databases (2010-2012). Climate data obtained from the National Oceanic and Atmospheric Administration (NOAA) were compared to population adjusted county operative stone burden, controlling for patient and county demographic data as potential confounders. Results: A total of 63,994 unique patients underwent stone procedures in California between 2010 and 2012. Multivariate modeling revealed that higher precipitation (0.019 average increase in surgeries per 1000 persons per inch, p < 0.01) and higher mean temperature (0.029 average increase in surgeries per 1000 persons per degree, p < 0.01) were both independently associated with an increased operative stone disease burden. Controlling for county-level patient factors did not change these observed effects. Conclusions: In the state of California, higher precipitation and higher mean temperature are associated with increased rates of stone surgery. Our results appear to agree with the larger trends seen throughout the United States where the areas of highest stone prevalence have warm wet climates and not warm arid climates.