Warmer Weather and the Risk of Urinary Tract Infections in Women

The incidence of urinary tract infections is seasonal, peaking in summer months. One possible mechanism for the observed seasonality of urinary tract infections is warmer weather.

We identified all urinary tract infection cases located in approximately 400 metropolitan statistical areas in the contiguous United States between 2001 and 2015 using the Truven Health MarketScan® databases. A total of 167,078,882 person-years were included in this data set and a total of 15,876,030 urinary tract infection events were identified by ICD-9 code 599.0. Weather data for each metropolitan statistical area and date were obtained from the National Centers for Environmental Information. We computed the mean temperature during the period 0 to 7 days prior to the urinary tract infection diagnosis. We used a quasi-Poisson generalized linear model. The primary outcome was the number of urinary tract infections each day in a metropolitan statistical area in each age group. Covariates considered included age group, day of week, year and the temperature during the previous 7 days.

Warmer weather increases the risk of urinary tract infections among women treated in outpatient settings in a dose-response fashion. On days when the prior week's average temperature was between 25 and 30C, the incidence of urinary tract infections was increased by 20% to 30% relative to when the prior week's temperature was 5 to 7.5C.

The incidence of urinary tract infections increases with the prior week's temperature. Our results indicate that warmer weather is a risk factor for urinary tract infections. Furthermore, as temperatures rise, the morbidity attributable to urinary tract infections may increase.