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Sources of Funding: none

Introduction

It is commonly accepted that increased temperatures are associated with increased prevalence of kidney stone disease. When examining stone mapping studies of the United States, while some regions with high annual temperatures (the southeast) have higher kidney stone prevalence, other warm regions such as the southwest do not. One major climate difference between these two regions is annual precipitation and humidity. We sought to explore the associations among, temperature, precipitation and urinary stone disease.

Methods

We identified all patients who underwent ureteroscopy, percutaneous nephrolithotomy, or shock wave lithotripsy using data from the Office of Statewide Health Planning and Development (OSHPD) for the state of California (2010-2012). We calculated the rate of operative stone disease for each county based on the patient’s home zipcode. We obtained climate data for each county in California from the National Oceanic and Atmospheric Administration. We compared the rate of urinary stone surgeries, adjusted for county population, mean annual temperature, total number of days over 90 degrees, and the total annual precipitation.

Results

A total of 63,994 unique patients underwent stone procedures in California between 2010-2012. The mean county stone surgery rate was 1.77 cases per 1000 persons (range 0.05-3.16). In the lowest quartile of rainfall (less than 21 inches per year), the average stone surgery rate was 1.5 per 1000 persons. This was significantly less than 2.2 per 1000 persons in the regions with the highest quartile of rainfall (44 inches per year) (p<0.01). In fully-adjusted models, precipitation (0.019 increase in surgeries per 1000 persons per inch, p<0.01) and higher mean temperature (0.029 increase in surgeries per 1000 persons per degree, p<0.01) were associated with an increased rate of stone surgery (Figure 1). The effect of temperature was not significant unless precipitation was controlled for.

Conclusions

In the state of California, temperature alone is not associated with the county-level rate of stone surgery until precipitation is included in models. Our results appear to agree with the larger trends seen through the United States where the areas of highest stone prevalence have warm humid climates, and not warm arid, climates.

Funding

none