For Immediate Release: May 16, 2017
Society for Healthcare Epidemiology of America
Contact: Tamara Moore / tmoore@thereisgroup.com / 202-868-4008
Author Contact: Tony Craine / tony-craine@uiowa.edu / 319-356-7127

Warm Weather Increases the Incidence of Serious Surgical Site Infections

Major survey research shows that risk rises with temperatures

NEW YORK (May 16, 2017) – Surgical site infections, a common healthcare-associated infection, are seasonal – increasing in the summer and decreasing in the winter–according to new research published online today in Infection Control & Hospital Epidemiology, the journal of the Society for Healthcare Epidemiology of America. Temperatures above 90°F were associated with 28.9 percent increased odds for hospitalization with a surgical site infection (SSI) compared to temperatures less than 40°F.

“We show that seasonality of surgical site infections is strongly associated with average monthly temperature. As temperatures rise, risk increases,” said Philip M. Polgreen, MD, senior author of the study, Director of the Innovation Lab at The Signal Center for Health Innovation and Associate Professor of Internal Medicine and Epidemiology at the University of Iowa. “However, the odds of any one person getting an infection are still small, and due to the limitations of our data, we still do not know which particular surgeries or patients are at more risk from higher temperature.”

Researchers used data on millions of patients from the Nationwide Inpatient Sample – the largest database of discharges from hospitals in the United States – to identify every adult hospitalization with a diagnosis of SSI from January 1998 to November 2011. Each hospital’s longitude and latitude were used to identify nearby weather stations. Monthly summary statistics from each station were included in the analysis, including temperature, rainfall and wind speed. In addition to reviewing incidence of SSIs in a linear time trend to determine the role of seasonality, the study included subgroup analyses by hospitals’ region, teaching status and setting (i.e., urban vs. rural), as well as patient gender and age.

SSIs were found to be seasonal, with 26.5 percent more SSI-related hospital discharges in the peak month of August than at the low point of January. Researchers estimated that a 25 percent reduction in the average number of at-risk surgeries in the months of July and August would be associated with a decrease of nearly 1,700 SSIs each year. Seasonality and incidence were similar across all regions, age groups, genders and hospital teaching categories, but seasonality was greatest among patients in their 40s and 50s.

“These results tell us that we need to identify the patients, surgeries, and geographic regions where weather-related variables are most likely to increase patients’ risk for infections after surgery,” said Christopher A. Anthony, MD, the first author of the study and surgery resident physician at University of Iowa Roy J. and Lucille A. Carver College of Medicine. “This way, we can identify the patients at the greatest risk for surgical site infections during warmer summer months.”

SSIs can be a major cause of severe illness or death after surgery. SSIs also cause increased use of antibiotics and other antimicrobials, and are a leading cause of hospital readmissions, contributing to excess healthcare costs.

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Christopher Anthony, Ryan Peterson, Linnea Polgreen, Daniel Sewell, Philip Polgreen. “The seasonal variability in surgical site infections and the association with warmer weather: a population-based investigation.” Web (May 16, 2017).

About ICHE
Published through a partnership between the Society for Healthcare Epidemiology of America and Cambridge University Press, Infection Control & Hospital Epidemiology provides original, peer reviewed scientific articles for anyone involved with an infection control or epidemiology program in a hospital or healthcare facility. ICHE is ranked 19th out of 83 Infectious Disease Journals in the latest Web of Knowledge Journal Citation Reports from Thomson Reuters.

The Society for Healthcare Epidemiology of America (SHEA) is a professional society representing more than 3,000 physicians and other healthcare professionals around the world who possess expertise and passion for healthcare epidemiology, infection prevention, and antimicrobial stewardship. The society’s work improves public health by establishing infection-prevention measures and supporting antibiotic stewardship among healthcare providers, hospitals, and health systems. This is accomplished by leading research studies, translating research into clinical practice, developing evidence-based policies, optimizing antibiotic stewardship, and advancing the field of healthcare epidemiology. SHEA and its members strive to improve patient outcomes and create a safer, healthier future for all. Visit SHEA online at www.shea-online.org, www.facebook.com/SHEApreventingHAIs and @SHEA_Epi.

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