Canadian researchers analyzed data on the five most common injuries that occurred during two National Football League seasons between 2012 and 2014.
Players had twice the risk of concussion and a 1.5 times higher risk of ankle injuries when the temperature was 50 degrees Fahrenheit (10 degrees Celsius) or colder, compared to games played in 70 degrees (21 degrees Celsius), the findings showed.
The researchers also found that players were 1.36 times more likely to suffer shoulder injuries during games played on natural grass instead of synthetic turf.
"There has been a lot of discussion recently about the significant risk of injury in the NFL and general player safety, particularly regarding concussions," said lead study author Dr. David Lawrence, a clinical fellow at St. Michael's Hospital in Toronto.
"The first step in improving player safety and lowering that risk is to identify the factors affecting injury rates. Once we can answer those questions, we can begin to modify player exposure," he said in a hospital news release.
"There is limited research looking at the external risk factors for injuries in the NFL," Lawrence said. "Given this is one of the first studies to look at these variables, we can only speculate at this time on the underlying causes for the associations we observed with specific injuries on game days."
For example, equipment may have less give at colder temperatures, which may increase the force of impact, the researchers suggested. Players may be more likely to report injuries during colder games because they tend to have more contact with athletic staff when it's colder. It's also possible that in warmer weather, players may mistake concussion symptoms for heat-related illness.
"Our findings contribute to the growing body of evidence surrounding this topic, but further research is needed," Lawrence said.
"Applying this information may help inform future injury prevention strategies in the NFL, or other professional sports, and highlight the effects of these seemingly small external factors," he added.
The study was published in the March 31 issue of the Orthopaedic Journal of Sports Medicine.
The American Academy of Family Physicians has more on concussion.
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