Neurobiologist Allison Brager knows the effects of sleep deprivation first hand. When the Army officer and chief of the Sleep Research Center at the Walter Reed Army Institute of Research traveled to Kuwait earlier this year to monitor sleep habits among soldiers, she stayed awake for 45 hours straight as she traveled with a unit engaged in a marksmanship exercise. “When we came off the range in the morning and traveled back to the base, I felt shaky,” she tells The Scientist. “Physiologically, I didn’t feel right.”

But these are the conditions soldiers deal with repeatedly throughout their careers. In addition to sleep deprivation, combat personnel are at high risk of traumatic brain injury, either as a result of explosive devices or from the kickback on shoulder-mounted munitions, Brager explained today (November 5) at a press conference at the annual Society for Neuroscience conference...

To understand how traumatic brain injury and sleep deprivation might interact, Brager and her colleagues recruited seven volunteers who’d experienced concussions (mostly due to sports injuries, though one participant did have a blast-induced trauma) and six healthy controls to go 40 hours without sleep. After the subjects slept, the researchers then tested their reaction times to a prompt on a screen, and found that concussed individuals responded about 100 milliseconds (ms) slower and had more false starts than those who did not have a history of head trauma.

“We saw that the brain began to unravel in terms of performance,” Brager said at the press conference. “In a combat situation, that [100 ms delayed reaction] can be the difference between life and death.”

Part of the reason for this cognitive deficit may involve the fact that concussed participants spent significantly less time in deep non-REM (NREM) sleep following sleep deprivation, says Brager. “If you’re getting less [NREM] sleep after concussion, that provides less opportunity to have these restorative effects of sleep.”

Understanding how soldiers with brain injuries respond to sleep deprivation is critical to optimizing military performance and health, Brager adds. “At the end of the day, the Army’s not going to change how it fights. . . . We’re not going to change the way war’s fought so we have to [apply] what we know about sleep to work around that.”

Correction (November 13, 2020): This story has been updated to clarify that all subjects were sleep deprived; controls didn’t have a history of brain trauma. The Scientist regrets the error.

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