US Army soldiers sleep in their chairs after returning to base during a 24 hour Cavalry Spur Ride. (Photo Credit: Reuters)
Healthy adults who get at least eight hours of sleep a night may be less likely to experience common exercise-related injuries like fractures, sprains and muscle strains, a study of US soldiers suggests. Based on survey data for 7,576 men and women in the Army's Special Operations Forces, soldiers who got no more than four or five hours of sleep a night were more than twice as likely to report a musculoskeletal injury in the past 12 months as those who slept eight hours or longer.
"Adequate amounts of sleep, especially among active athletes, have not only been shown to improve physical performance and health but may also now have a positive impact on musculoskeletal injury prevention," said study coauthor Tyson Grier of the U.S. Army Public Health Center at Aberdeen Proving Ground in Maryland.
Over the year-long study, more than half of the soldiers said they had experienced at least one musculoskeletal injury.
Most participants, about 63%, got six or seven hours of sleep a night. About 10% got no more than four hours, and only 16% got at least eight hours.
Compared to people who reported eight hours or more of sleep each night, soldiers who slept seven hours were 24% more likely to experience a musculoskeletal injury. The risk climbed as sleep declined, with a 53% greater injury risk at six hours of sleep, a doubled risk at five hours of sleep and 2.4 times the risk at four hours or less.
Musculoskeletal conditions can include everything from a sprained ankle to a torn rotator cuff or herniated disc in the spine. Causes of injury are just as wide-ranging, and can include high-intensity exercise, a physically demanding job or too many hours typing at a computer.
In the Army, two-thirds of injuries are musculoskeletal overuse injuries, mostly attributed to physical training or repetitive activities, the study team writes in the journal Sleep Health.
With some 42% of Army personnel reporting an average five hours of sleep or less, making sure soldiers get adequate rest could be a way to reduce injury risk, they add.
One limitation of the analysis is that researchers relied on soldiers' report of how long they slept. Further research would also be needed to test whether increasing sleep time really reduces injuries.
It's possible that too little sleep leads to decreased alertness and attention that makes people more likely to get hurt, said Dr. Hohui Wang of the University of California, San Francisco, who wasn't involved in the study. "Additionally, sleep loss causes cell damage in multiple organs," Wang said by email. Catching up on sleep might help reverse this cell damage.
Most people are healthiest and perform their best with seven to nine hours of sleep a night, said Captain Jeffrey Osgood of the Walter Reed Army Institute of Research in Silver Spring, Maryland.
"If someone is getting six or fewer hours of sleep per night on a regular basis, or if they are having a hard time getting to sleep, staying asleep, or waking up too early, they should prioritize taking steps to improve their sleep," Osgood, who also wasn't involved in the study, said by email.
"Try to avoid caffeine, nicotine, and exercise in the hours leading up to sleep; avoid using alcohol as a sleep aid; don't go to bed hungry; try to keep your bedroom dark and quiet; use sleep masks and/or earplugs if needed; and keep your smartphone/devices out of bed," Osgood advised.