Monthly variations in urolithiasis presentations and their association with meteorologic factors in New York City.

Introduction: Nephrolithiasis in the United States has been on the rise during the past several decades. Temperature has been shown to directly correlate with increased stone disease. We examine the association between climactic factors and monthly urolithiasis presentation rates for 6 years at a single institution in New York City.

Methods: Emergency department (ED) data on patient visitations were collected along with patient demographics. Meteorological data were collected using the website "Weather Underground" ( www.wunderground.com ). Average monthly temperature, dew point, precipitation, and sea level pressure were obtained and relative humidity was calculated using the dew point. Monthly urolithiasis visitations and the correlation of atmospheric factors were analyzed using an autoregressive integrated moving average (ARIMA) model.

Results: The total number of renal colic visits to the hospital's ED from January 2007 through December 2012 tallied 3647 visits. The lowest average monthly rate per 1000 ED visits occurred in the month of February (28.8) and the highest in the month of August (43.8). There was a strong correlation between monthly presentation rate and temperature (P<0.01) and relative humidity (P=0.06) but no correlation with precipitation and sea level pressure. On multivariate ARIMA analysis, only average monthly temperature was significantly associated with monthly urinary calculi presentation rate among all comers (P<0.01). The crude correlations held true for both sexes with respect to temperature but not for females in regard to relative humidity. The age groups of 21 to 44 and 45 to 64 had a rate correlation with temperature and all races correlated with temperature, but only Caucasians had a weak correlation with relative humidity.

Conclusions: This is the first study examining the role of climate on stone presentation rate in a large city above the Southern "stone belt" states. Temperature has a strong correlation with calculi presentation rate, and relative humidity has a trend toward overall calculi presentation rate.