Ambient temperature and the risk of renal colic: a population-based study of the impact of demographics and comorbidity

Purpose — To examine the impact of ambient temperature on the incidence of emergency department admissions for acute renal colic and the potential influence demographics and comorbid conditions may have on this.

Methods — We conducted a population-based time series analysis using linked healthcare databases in Ontario, Canada that included all residents, aged ≥19, who were admitted to an emergency department from April 2002 to December 2013. The primary outcome was daily number of renal colic emergency-department admissions. A distributed lag non-linear model with 21 days of lag was applied to estimate the cumulative effect of temperatures on colic admissions. We estimated risks for cold and heat, defined as temperatures below and above the optimal temperature, which corresponded to the point with minimum risk of colic admissions. We conducted stratified analyses using selected demographics and comorbidities.

Results — During the study period 423,396 patients presented to an emergency department with colic. There was a significantly increased risk of colic as ambient temperature increased (rate ratio [RR]=1.30, 95% CI: 1.20-1.42). Subgroup analysis demonstrated an increased risk associated with heat for both genders, however this risk was more pronounced in males with extreme heat (RR=1.64 vs. 1.22, p=0.006). In contrast to other age groups, there was an increased risk for those in their 40's (RR=1.42), 50's (RR=1.54) and 60's (RR=1.31) (p=0.02).

Conclusion — Increasing ambient temperature was associated with increased risk of emergency department visits for colic, particularly in males and those aged 40-69.