SILVER SPRING, Md. -- U.S. service members who perform duties in cold weather climates face increased risk of injury from exposure to freezing conditions and wet environments. The Department of Defense conducts continuous surveillance to reduce the impact of cold weather on service members’ health and their mission accomplishment.

Overall incidence rates of cold injuries in U.S. service members declined during winter 2015-2016 after peaking in winter 2013-2014, when much of the eastern United States experienced much colder-than-average weather. This extreme cold was attributed to a weakening of the polar vortex, according to a recent analysis for the surveillance period 2011–2016.

The overall incidence rate for all active component service members in 2015-2016 (29.5 per 100,000 person-years [p-yrs.]) was 23 percent lower than the rate (38.2 per 100,000 p-yrs.) for the 2014-2015 cold season but slightly higher than the rates for the first two seasons of the surveillance period, according to a study published in Defense Health Agency’s Armed Forces Health Surveillance Branch (AFHSB) peer-reviewed journal, the Medical Surveillance Monthly Report.

During the 2015-2016 cold season, 447 members of the active (n=383) and reserve (n=64) components had at least one medical encounter with a primary diagnosis of cold injury. The numbers of affected individuals in both components were the lowest since the 2011-2012 cold season, when the total was 394.

“For many years, the U.S. Armed Forces have developed and improved robust training procedures and protective equipment and clothing to counter the threat from cold environments,” said Air Force Col. Dana Dane, the chief of the AFHSB’s Epidemiology and Analysis section. “However, it is important that awareness, policies, and procedures continue to be emphasized to reduce the toll of such injuries.”

Army service members who received at least one diagnosis of a cold injury (rate: 53.1 per 100,000 p-yrs.) during the 2015-2016 cold season accounted for 66.6% of active component members affected among all services. The 74 members of the Marine Corps diagnosed with a cold injury represented 19.3% of all affected active component service members. Navy service members (n=19) had the lowest service-specific rate of cold injuries during the 2015 - 2016 cold season (rate: 5.8 per 100,000 p-yrs.).

Frostbite was the most common type of cold injury (n=146 or 36.8% of all cold injuries) among active component service members. In the Air Force, 45.9% of all cold injuries were frostbite, whereas in the other services, the proportions of cases of frostbite ranged from 38.7% (Army) to 26.7% (Marine Corps). For the Navy and Air Force, the 2015-2016 numbers and rates of frostbite injuries in active component service members were the lowest of the past five years.

Females had higher rates for frostbite than males during the five-year surveillance period. This was mainly because of the striking difference between the rates for female (75.4 per 100,000 p-yrs.) and male (50.3 per 100,000 p-yrs) service members in the Army.

Because winter is a peak season for cold weather injuries among service members, healthcare providers and military leadership need to help service members and their families understand the importance of taking winter safety precautions and actively employing cold injury prevention strategies.

“Continuing education on cold weather preparation and the proper use of winter safety equipment could play a crucial role in military efforts to combat this threat to the health and operational effectiveness of U.S. Armed Forces, especially during training sessions and deployments,” Dane said.

Any individual exposed to cold conditions is at increased risk for cold injury -- ranging from military members, athletes, and civilian workers to children. For information on the medical, public health and military impact of cold weather injuries, read about the Defense Medical Surveillance System (DMSS) used for this analysis and the article Safeguarding readiness during winter.