Handheld Device Fights Fatigue by Stimulating Vagus Nerve

Feeling tired? Applying electricity to a nerve in the neck with a handheld device can reduce fatigue and improve multitasking in sleep-deprived people, according to a new study conducted on U.S. Air Force volunteers.

Previous research found that electrically stimulating the brain with a technique known as transcranial direct current stimulation can improve mental performance in a variety of ways, such as combating fatigue. Prior work suggested the benefits were rooted in the stimulation of a region in the brainstem known as the locus coeruleus, thought to play a key role in attention, wakefulness, memory formation and memory retention.

Still, although transcranial direct current stimulation is a non-invasive technique, it is difficult to use it by oneself and may require 30-minute doses to boost attention and vigor. As such, researchers wanted to find simpler, quicker methods to achieve similar results.

So scientists explored stimulating the vagus nerves that run from the abdomen into the locus coeruleus. Vagal nerve stimulation has been an FDA-approved medical treatment for epilepsy and depression for more than two decades, and recent work has found vagal nerve stimulation boosts memory and learning in both rats and humans.

In the new study, researchers experimented with a commercially available handheld device previously approved by the FDA to treat migraines and cluster headaches that delivers an electric current through the skin to the cervical vagus nerves in the neck.

In the experiment, 40 active-duty U.S. Air Force personnel stayed awake for 34 hours. Fatigue is an enduring issue within the military," says study co-author Andy McKinley, a biomedical engineer at the Air Force Research Laboratory at Wright-Patterson Air Force Base near Dayton, Ohio. There can be days at a time when sleep is rare, or you can't get good sleep due to environmental factors, or you go from a day shift to a night shift or a night shift to a day shift, and such large shifts in one's circadian cycle makes sleep difficult, and leads to a lot of fatigue as well."

The volunteers were tested at nine times during the experiment on four tasks that analyzed their ability to stay alert and multi-task. These included pressing a button as soon as they saw a light move a specific way and keeping track of multiple gauges, lights, sounds and other alerts to deal with simulated malfunctions and other challenges.

Twelve hours into the experiment, half the volunteers each received two minutes of electrical stimulation to the left cervical vagus nerve and two to the right, with two minutes of rest in between. The other half had a sham device that looked identical to the real machine pressed to their necks that made similar vibrations and clicking sounds but did not deliver any current. Both groups were asked to not nap or consume any caffeine or similar stimulants during the experiment.

The scientists found the volunteers who received vagus nerve stimulation performed better at tasks testing focus and multi-tasking. They also reported less fatigue and higher energy. These benefits peaked 12 hours after simulation, with boosts to alertness lasting for up to 19 hours. There was no apparent effect the device had on how well or how long the volunteers slept after the experiment, says study lead author Lindsey McIntire, a human factors psychologist at defense technology company Infoscitex in Dayton, Ohio.

There's chronic use of caffeine and energy drinks to make people perform better, but the more you use caffeine, the less effective it is. It only usually lasts a few hours, and it makes you jittery," McKinley says. The nice thing about this technology is that it's very easy to administer and its effects last much longer than we typically see with caffeine, and not only do they experience a performance improvement, but they feel better overall."

Outside of the military, this device could benefit many professions where fatigue is a serious and unavoidable problem, such as medicine and transportation, McIntire says. You can almost imagine this helping anywhere people are working in extreme environments, such as the arctic or space- NASA funded this study," she adds.

There is no research that McKinley has seen that suggests that such techniques might lead to addictive behavior. Still, I definitely think there should be guidelines on the number of doses per day a person should have," he says.

Future research can investigate how well this device can work on even greater levels of sleep loss, McKinley says. Further work can also explore the best time of day, frequency, duration and strength for doses of stimulation, test the device in messier and less controlled settings, and explore specifically what effects it has on the body and brain, the researchers say.

The scientists detailed their findings online June 10 in the journal Communications Biology.