NATICK, Mass. -- Could breathing reduced oxygen help warfighters recover from jet lag faster? In an effort to find out, U.S. Army and U.K. researchers recently conducted a jet lag study on British warfighters who traveled to the lush rainforests of Brunei.

You don't have to be a warfighter to understand how exhausting and debilitating jet lag can be.

Anyone who has traveled across multiple time zones has experienced varying symptoms of jet lag, including tiredness, fatigue, sleep difficulties, head ache, irritability and gastrointestinal distress. These symptoms can slow down vacations, plague athletes and performers and cause traveling employees to lose valuable work hours.

Unlike civilians, warfighters have to face rapid deployments across multiple time zones, and upon landing, they have to be physically and cognitively ready to accomplish their mission. That's not easy to do when you feel like you are in a fog and can barely keep your eyes open.

"Warfighters who experience jet lag are almost like casualties because they are incapacitated cognitively and physically, compromising mission readiness," said Dr. Beth Beidleman, one of the study's key investigators. "It has been shown that jet lag can affect warfighters' cognitive abilities, such as reaction time, memory, executive function and concentration. It can also affect physical ability to the point where warfighters are unable to do their jobs."

Beidleman, a research physiologist from the U.S. Army Research Institute of Environmental Medicine, or USARIEM, added that this study could be one of the first of many in which USARIEM researchers will partner with the U.K. Institute of Naval Medicine, or INM, and the Walter Reed Army Institute of Research, or WRAIR, to study the effectiveness of the reduced oxygen treatment.

"The goal of this study is to see if this reduced oxygen treatment is more effective than other jet lag remedies, such as caffeine, melatonin or pharmaceuticals," Beidleman said. "By leveraging our connections with Department of Defense and international collaborators, including the sleep research team at WRAIR and Dr. Simon Delves' INM research team, who work with British warfighters deploying to Brunei, we have been able to collect valuable jet lag data on warfighters."

To understand how people get jet lag, you have to picture your body as a clock. According to Beidleman, your brain contains a master circadian clock that regulates other clocks in your body. For about 24 hours every day, this circadian clock controls your bodily functions, temperature, heart rate, hormone levels and sleep. Particularly, it helps your body stay alert during the day and asleep during the night. Your circadian clock is entrained by the light-dark cycle, or when the sun rises and sets.

When you rapidly fly across several time zones, your circadian clock, which sends signals for sleep and wakefulness, does not match the local time of the place where you landed. This mismatch causes you to experience jet lag symptoms.

Your circadian clock and the light-dark cycle will gradually fall back in sync, but that takes time. Beidleman said the number of days it takes people's circadian clocks to recover from jet lag matches the number of hours between time zones. Brunei is eight hours ahead of the U.K. So, according to Beidleman, it would take about eight days for the British warfighters' internal circadian clocks and the external light-dark cycle to synchronize. Beidleman also added that flying eastward (such as from the U.K. to Brunei) is harder than flying westward. That's because your body's circadian clock is slightly longer than 24 hours. So when you fly east, you are shortening your days, which goes against what your body wants to do.

Beidleman pointed out that while pharmaceuticals and caffeine may help you sleep or stay awake, they do not actually reset your circadian clock. But there is evidence that leads researchers to believe that reduced oxygen can.

"Reduced oxygen causes your body to produce a molecule called HIF1α, properly known as Hypoxia Inducible Factor1-alpha," Beidleman said. "When you are in a low-oxygen environment, such as at high altitude, your body produces this signal molecule, which binds to your DNA and regulates over one hundred genes that help your body adapt to those conditions.

"Animal studies indicate that this same molecule sends signals to 'clock genes' that help your body adjust when you experience jet lag. We want to see if giving warfighters this reduced oxygen treatment could also reset the circadian clock and accelerate jet lag recovery by triggering production of HIF1α."

This reduced (14 percent) oxygen is similar to the quality of air you would breathe if you were standing 10,000 feet above sea level. Administered for 2 hours, this level of oxygen is not severe enough to cause acute mountain sickness. It's not only safe, but the technology to deliver reduced oxygen exists both commercially and within the military.

Before departing for Brunei, researchers assessed warfighters' sleep, physical activity, jet lag symptoms, cognitive performance and internal circadian rhythms in the U.K. Researchers were able to monitor warfighters' internal circadian rhythms by measuring their core body temperatures with physiological status monitoring systems. They also collected saliva samples in order to monitor warfighters' melatonin and cortisol levels while recovering from the long-distance travel.

"When your circadian clock operates normally, your core body temperature falls when you sleep and rises when you wake," Beidleman said. "Melatonin, a sleep aid, peaks when you are asleep, and cortisol, a stress hormone, peaks when you are awake. By monitoring those three things, we are able to assess how your circadian clock normally operates and how it operates when you experience jet lag."

Upon landing, the researchers divided the warfighters into two groups. One group received a single dose of the reduced oxygen treatment for two hours in the morning, while the other group received a placebo. The researchers tracked how long it took each group to recover from jet lag by collecting and comparing the same data they gathered before flying to Brunei. The USARIEM, WRAIR and INM researchers are now analyzing that data back in the lab.

"Jet lag is a problem anyone can face, but it becomes even more significant when warfighters' lives are at stake," Beidleman said. "Having this jet lag data is going to be extremely valuable for future research and development of jet lag interventions because it will enhance the capability of our warfighters to operate effectively across the spectrum of operations when the Army is in conflict."