Effects of sleep deprivation on the brain

Aug 7 2006

Everyone needs sleep, but temporary periods with no sleep can be a reality of military operations.

To get answers on sleep questions for the military as well as civilians, for nearly four years Dr. Sean Drummond, a Department of Defense-funded researcher, has studied the effects of sleep deprivation on the brain, namely in decision making, as well as how long it takes to recover from periods of no sleep.

"We can't keep as many things online at any one time when we're sleep deprived. Sleep deprivation significantly impairs attention, working memory performance, our ability to drive. It has the same effect as alcohol does," said Drummond, who works with the University of California San Diego and the Veterans Affairs San Diego Healthcare System.

In the May issue of Flying Safety Magazine, Capt. Brain Drummond, a pilot in a KC-135 air refueling tanker in Iraq recounted a potentially accident-causing mistake he made in March during a refueling mission when he let too much fuel out of a tank, causing an imbalance in the aircraft. He believes the mistake resulted from too many missions with too little sleep. After flying 12 six- to seven-hour missions and fulfilling all the briefing, debriefing and aircraft pre- and post-flight requirements, he recalled that he and the crew looked like "the walking dead."

"I don't think you really know the fatigue that sets into your body until you are finally able to rest," he said. "Even though I was getting enough rest at night during the 11 straight sorties, my body and senses became very numb. I truly believe, because of the demand for the missions in OIF (Operation Iraqi Freedom), our crew had become so tired that we forgot the little things, which can add up to big things."

Because of incidents like Drummond's the DoD's Peer Reviewed Medical Research Program funds research like Drummond's. Congress created the program in 1999 to promote research in health issues the military faces. Since its inception through 2005, the program has spent almost $300 million to fund nearly 200 projects in a range of medical topics, including combat casualty care and technology and infectious disease research.

The researcher and his team recruited 40 volunteers with good sleep habits who agreed to live in a lab for six days. For their stay, volunteers lived two normal days and nights, stayed awake for 64 hours and then were allowed again to sleep so the team could observe the recovery process.

During the volunteers' awake hours, they underwent half-hour long learning, memory and decision-making tests every two hours to see how well they fared at different stages of sleep deprivation. One test, for example, had the volunteers memorize lists of nouns. Drummond and his team also used functional magnetic resonance imaging in the morning and evening to map the brain's reaction. The imaging technique looks at oxygen use in the brain, so whatever part of the brain is being used, it needs more oxygen.

"The brain is a system, a network of areas, all of which work together to get a task done," he said.

The researcher found that volunteers' working memory wasn't affected after 36 hours without sleep, not because they were all healthy and had an average age of 24 years, but because other regions of the brain jumped in to help.

"The brain can actually compensate for this level of sleep deprivation. Areas that don't normally turn on when a person is well rested came online when the person was sleep deprived," Drummond said. "The better they're able to engage them, the better they're able to do after sleep deprivation."

After 60 hours, though, most volunteers didn't fare as well on their tests as they had at the 36-hour mark. After two and a half days without sleep, their brains could not recruit help.

"I think it will be important to use these data to try to better predict and understand who is going to be resilient to sleep loss and who is going to be vulnerable," Drummond said. "The benefits will come in better understanding the consequences of sleep deprivation for more complex types of cognitive functions -- as opposed to simple attention, for example -- as well as better understanding how long the recovery process takes."

Drummond's team also found that recovering from 64 hours of sleep loss wasn't as simple as getting a few good nights' rest.

"We found on some tasks that people aren't back at the baseline level even after two full nights of sleep, given that they only lost two nights of sleep," he said. "Given the pervasiveness of inadequate sleep in the military and civilian worlds alike, there is clearly a need to understand what this is doing and can it be counteracted."