The impact of climate factors on the prevalence of urolithiasis in Northern Taiwan

Background: Urolithiasis is a common disease with high prevalence and recurrence. Its incidence varies in different geographic locations, and there are evidences that meteorological factors also affect urinary stone formation. The aim of this study is to analyze the effects of climate parameters on the numbers of shockwave treatments for urinary stones in our hospital, in order to understand the effects of these parameters on the prevalence of urolithiasis in northern Taiwan. Methods: We retrospectively reviewed the records of extracorporeal shockwave lithotripsy (ESWL) performed in our hospital from December 2006 to November 2011. Repeated ESWL performed in the same patient within 1 month was excluded, and we only counted as one ESWL in our study. Climate data of the corresponding months were collected from Central Weather Bureau. The available monthly meteorological data included highest, lowest, and average temperatures, humidity, rainfall, total rain days, sunshine hours, average atmospheric pressure, and wind speed. Results: Monthly ESWL number was positively correlated to temperature (r = 0.696), sunshine hours (r = 0.515), and wind speed (r = 0.369), while it was negatively correlated to humidity (r =-0.441) and atmospheric pressure (r =-0.568). Average monthly temperature had the strongest correlation to ESWL number (r² = 0.484). Monthly rainfall and rain days were not significantly correlated to ESWL number. To investigate the climate parameters together, we introduced these correlated factors into the multivariate linear regression model which demonstrated only temperature (ß = 1.438, 95% CI: 3.703-9.144, p < 0.001) and atmospheric pressure (ß = 0.803, 95% CI: 0.790-5.428, p = 0.010) to be independently related to monthly ESWL number. Conclusion: Temperature and atmospheric pressure are associated with monthly ESWL number. Ambient temperature is the most important climate factor affecting the prevalence of urolithiasis in northern Taiwan.