The promise of a quick boost has made caffeine-rich energy drinks all the rage among soldiers in combat zones.
The troops endure long hours under difficult conditions. But those convenient pick-me-ups could come with a steep price: difficulty sleeping.
Soldiers in Afghanistan who consumed three or more energy drinks daily were more likely to sleep fewer hours and have their sleep disrupted because of stress or illness, researchers found.
The findings come from a study led by the Walter Reed Army Institute of Research, published in the Centers for Disease Control and Prevention's Morbidity and Mortality Weekly Report.
Sleep can be luxury in a combat zone. Less than half the 988 U.S. Army and Marine soldiers surveyed by researchers in 2010 reported sleeping more than five hours a night.
But the sleep situation was worse for the survey's frequent consumers of energy drinks. They were almost twice as likely to report sleeping only three to four hours regularly. These sleep-deprived soldiers were twice as likely to doze off while on guard duty or when attending briefings.
It's unclear, however, whether the energy drinks are contributing to sleeplessness or a reflection of it. "It is likely to be a circular effect," according to psychologist and study co-author Robin L. Toblin of Walter Reed's military psychiatry branch.
"If too many are consumed, it very likely will make it harder to sleep, but it is also likely that those who feel tired or that they need to stay awake might be more likely to consume [the drinks]," she writes in an email. "And then that pattern would continue."
Energy drinks are easy for a soldier to find, even in a combat zone. They are distributed in base dining facilities and are a frequent addition to care packages. There are even brands, like RuckPack, formulated with soldiers in mind.
The drinks' portability and the variations in size and caffeine content ranging from the equivalent of one to more than five cups of coffee can make them more appealing than the traditional cup of joe. "They are grab-and-go ready, whereas coffee takes time to make," Toblin says.
Almost 45 percent of service members in the study's survey of U.S. Army and Marine platoons in Afghanistan reported drinking at least one of these beverages a day, and 13.9 percent drank three or more. That's much higher than in the general public. Other studies have found that 6 percent of young men consume these drinks daily.