Daily Mean Temperature Affects Urolithiasis Presentation in Seoul: a Time-series Analysis

Abstract

This study aimed to investigate the overall cumulative exposure-response and the lag response relationships between daily temperature and urolithiasis presentation in Seoul. Using a time-series design and distributing lag nonlinear methods, we estimated the relative risk (RR) of urolithiasis presentation associated with mean daily temperature, including the cumulative RR for a 20 days period, and RR for individual daily lag through 20 days. We analyzed data from 14,518 patients of 4 hospitals emergency department who sought medical evaluation or treatment of urolithiasis from 2005-2013 in Seoul. RR was estimated according to sex and age. Associations between mean daily temperature and urolithiasis presentation were not monotonic. Furthermore, there was variation in the exposure-response curve shapes and the strength of association at different temperatures, although in most cases RRs increased for temperatures above the 13°C reference value. The RRs for urolothiasis at 29°C vs. 13°C were 2.54 in all patients (95% confidence interval [CI]: 1.67-3.87), 2.59 in male (95% CI, 1.56-4.32), 2.42 in female (95% CI, 1.15-5.07), 3.83 in male less than 40 years old (95% CI, 1.78-8.26), and 2.47 in male between 40 and 60 years old (95% CI, 1.15-5.34). Consistent trends of increasing RR of urolithiasis presentation were observed within 5 days of high temperatures across all groups. Urolithiasis presentation increased with high temperature with higher daily mean temperatures, with the strongest associations estimated for lags of only a few days, in Seoul, a metropolitan city in Korea.

Keywords: Interrupted Time Series Analysis; Temperature; Urolithiasis.

Fig. 1

Lag-response association at different temperatures and exposure-lag response surface. (A) Lag response between 27, 29, and 31°C (mean) day and urolithiasis presentation relative to 13°C over a 20-day period in all patients, males, females, males younger than 40 years old, males between 40 and 60 years old, and males older than 60 years old in Seoul from 2005 to 2013. For each group, the estimated RRs of urolithiasis presentation in association with a daily mean temperature of 27, 29, and 31°C (relative to 13°C) for each lag day form temperature exposure during a 20-day are shown. (B) Risk of urolithiasis presentation relative to 10°C along temperature and a 20-day lag period in all patients, males, females, males younger than 40 years old, males between 40 and 60 years old, and males older than 60 years old in Seoul from 2005 to 2013. The 3-dimentional relationships include temperature (x-axis), lag (z-axis), and RR of urolithiasis presentation (y-axis). The point estimate of the relative risk (RR) of urolithiasis presentation at each point in the temperature range and lag window is shown using 13°C as the reference temperature.