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SAN FRANCISCO -- On days with higher average temperatures, there was a higher incidence of urinary tract infections (UTI), a researcher said here.

There was a on the risk of UTIs, and there was a dose-response relationship between average temperature and the number of UTIs, relative to times when the average temperature was about 4o to 45 degrees Fahrenheit (baseline) 3 to 8 days prior, reported Jacob Simmering, PhD, of the University of Iowa in Iowa City, at ID Week, with joint sponsorship by the (IDSA), the (PIDS), the (SHEA), and the (HIVMA).

The link between hydration and the risk of UTIs has been in some of the literature, and Simmering said the current study results could potentially provide some evidence for this hydration hypothesis with UTI risk.

"One of the implications we drew from this, that surprised us, is that the dose-response pattern kicked in at what we think of as relatively mild temperatures," Simmering told 名媛直播. "We think of heat-related illness as more extreme levels of heat, but ... this hydration effect, if that's what's driving this, seems like it's kicking in at lower temperatures than we think."

Simmering's group synthesized data from a number of sources. They examined all UTI cases in one of 397 metropolitan statistical areas (MSA) in the U.S. from 2011 to 2016, using the Truven MarketScan database. UTI cases were defined by ICD-9 and ICD-10 codes on insurance claims. They then obtained data on the weather for each MSA and date from the National Centers for Environmental Information. Data was adjusted for MSA size, day-of-week, and week-of-year.

Overall, there were almost 22 million outpatient claims for UTI within the study period. Simmering noted that there was no microbiologic data collected, only insurance information.

Hotter MSAs on average appeared to have more cases of UTIs. Simmering said that for each degree an MSA was hotter than other MSAs, on average there were 6% more cases of UTIs (RR 1.06, 95% CI 1.06-1.06 per °F). Similarly, within an MSA, hotter days had more cases of UTIs than typical days, with Simmering explaining that "in a period where the previous week was 1° warmer than it would've normally been, we saw a 3% increase in the incidence of UTIs" (RR 1.03, 95% CI 1.03-1.05 per °F above MSA-median temperature).

Simmering said that the dose-response curve started at about an average temperature of 50 degrees, where "people expect to change their behavior."

"They're going outside, they're being more active, they're sweating and their hydration goes down," he said.

Sensitivity analyses found that this was even true in "places without seasons," such as coastal California and coastal Florida, or places with "very small seasonal variations," defined as >10° between the coldest 25th percentile day and the hottest 75th percentile day.

Simmering concluded there was a "biologically plausible increase" in UTI incidence, stating that "the temperature of the prior week is associated with UTI risk, and it seems to be causal."

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