Surgical site infections are as seasonal as allergies, warmer weather increases risk

Allergies aren’t the only thing that are seasonal. In a study published in Infection Control & Hospital Epidemiology, researchers found the risk of developing surgical site infections (SSI) increased as the weather warms up.

Analyzing millions of data records from January 1998 to November 2011 from the Nationwide Inpatient Sample, a database of discharges from hospitals, researchers identified patients that developed SSIs and compared those numbers to monthly statistics of temperature, rainfall and wind speed.

Results showed rates of developing an SSI were seasonal, increasing by 26.5 percent during the summer months. At temperatures over 90 degrees, the risk increased to 28.9 percent when compared to 40 degrees.

"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 and 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."

By reducing the numbers of at-risk surgeries by 25 percent during the summer months, researcher estimated 1,700 cases of SSIs could be prevented annually.

"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. "This way, we can identify the patients at the greatest risk for surgical site infections during warmer summer months."