title: Daily mean temperature and clinical kidney stone presentation in five U.S. metropolitan areas: a time-series analysis.
abstract: BACKGROUND
  High ambient temperatures are a risk factor for nephrolithiasis, but the precise relationship between temperature and kidney stone presentation is unknown.
  
  
  OBJECTIVE
  Our objective was to estimate associations between mean daily temperature and kidney stone presentation according to lag time and temperatures.
  
  
  METHODS
  Using a time-series design and distributed lag nonlinear models, we estimated the relative risk (RR) of kidney stone presentation associated with mean daily temperatures, including cumulative RR for a 20-day period, and RR for individual daily lags through 20 days. Our analysis used data from the MarketScan Commercial Claims database for 60,433 patients who sought medical evaluation or treatment of kidney stones from 2005-2011 in the U.S. cities of Atlanta, Georgia; Chicago, Illinois; Dallas, Texas; Los Angeles, California; and Philadelphia, Pennsylvania.
  
  
  RESULTS
  Associations between mean daily temperature and kidney stone presentation were not monotonic, and there was variation in the exposure-response curve shapes and the strength of associations at different temperatures. However, in most cases RRs increased for temperatures above the reference value of 10°C. The cumulative RR for a daily mean temperature of 30°C versus 10°C was 1.38 in Atlanta (95% CI: 1.07, 1.79), 1.37 in Chicago (95% CI: 1.07, 1.76), 1.36 in Dallas (95% CI: 1.10, 1.69), 1.11 in Los Angeles (95% CI: 0.73, 1.68), and 1.47 in Philadelphia (95% CI: 1.00, 2.17). Kidney stone presentations also were positively associated with temperatures < 2°C in Atlanta, and < 10°C in Chicago and Philadelphia. In four cities, the strongest association between kidney stone presentation and a daily mean temperature of 30°C versus 10°C was estimated for lags of ≤ 3 days.
  
  
  CONCLUSIONS
  In general, kidney stone presentations increased with higher daily mean temperatures, with the strongest associations estimated for lags of only a few days. These findings further support an adverse effect of high temperatures on nephrolithiasis.
authors.affiliation: Division of Urology, Department of Surgery, The Children's Hospital of Philadelphia, Philadelphia, Pennsylvania, USA.
authors.forename: Gregory E
authors.initials: GE
authors.lastname: Tasian
authors.forename: Jose E
authors.initials: JE
authors.lastname: Pulido
authors.forename: Antonio
authors.initials: A
authors.lastname: Gasparrini
authors.forename: Christopher S
authors.initials: CS
authors.lastname: Saigal
authors.forename: Benjamin P
authors.initials: BP
authors.lastname: Horton
authors.forename: J Richard
authors.initials: JR
authors.lastname: Landis
authors.forename: Rodger
authors.initials: R
authors.lastname: Madison
authors.forename: Ron
authors.initials: R
authors.lastname: Keren
mesh_terms: D002947:Cities / Q000453:epidemiology; D002980:Climate; D004781:Environmental Exposure / Q000706:statistics & numerical data*; D005260:Female; D006801:Humans; D007669:Kidney Calculi / Q000453:epidemiology*; D008297:Male; D012307:Risk Factors; D013696:Temperature; D013997:Time Factors; D014481:United States / Q000453:epidemiology