Jet lag is a familiar hazard for those who take long flights. Now, it turns out, the remedy may be in the very air we breathe.
Scientists in Israel (with help from a colleague in the U.K.) have found that reducing atmospheric oxygen levels shaved days off the time that mice took to adjust to a big time shift. This suggests that it may someday be possible to offer travelers a low-oxygen lounge, or even lower the oxygen in baggage-claim areas, to help travelers combat discombobulation.
Jet lag arises from the clash of biology and technology. Most light-sensitive creatures have what’s known as a circadian clock—an internal timing system that uses light and other cues to synchronize with geophysical time. But when you move quickly across time zones, your body takes awhile to catch up with the day-night cycle in your new location.
In mammals, a master clock in the brain responds mainly to light, but cells throughout the body have their own internal clocks, typically synchronized through feeding patterns and temperature changes (which usually correlate with time of day). Since oxygen absorption varies with food intake and body temperature, researchers at the Weizmann Institute of Science in Rehovot, Israel, wondered whether oxygen itself might be a synchronizing cue in circadian rhythms.
To test this idea, the scientists suddenly shifted forward the day-night schedule of mice by six hours—simulating what would happen if the mice had flown from New York to Paris. Some of the mice were kept in a normal atmospheric environment of 21% oxygen, but others spent 12 hours in an environment of just 16% oxygen before the time-shift. That reduced level approximates the air in a commercial jetliner, says one of the scientists, Yaarit Adamovich.
Mice that received the low-oxygen treatment adjusted to the new time in four to five days—three days faster than mice left in a normal atmospheric environment. (This suggests that time spent in a jet may actually mitigate the effects of jet lag.) But the scientists found that they could get the same three-day speedup in adjustment by keeping the mice at 14% oxygen for just two hours after the time-shift, implying that jet-lagged travelers might benefit from a low-oxygen environment after landing.
Why does oxygen reduction help so much? The answer isn’t completely clear, but it probably relates to a protein called HIF-1-alpha, which regulates cellular responses to changing oxygen levels. Jet-lagged mice deficient in this protein were not helped by oxygen reduction.
The scientists hope to extend the research by trying their system on humans subjects, Dr. Adamovich says. Meanwhile, they have a hunch that temporarily raising oxygen levels would have the same effect as temporarily lowering them. Preliminary results support the notion that perhaps what helps to reset the body’s clock is changing oxygen levels in any direction, rather than just slashing them. Higher oxygen would be safer for individuals with heart or lung ailments that could be exacerbated by reduced oxygen.
This research could have implications beyond jet travel. Electric lights, caffeine and shifting work schedules can throw off circadian rhythms without flying, but those who suffer jet lag in place don’t get the accidental oxygen therapy that travelers appear to be receiving when they fly.
“Rhythmic Oxygen Levels Reset Circadian Clocks Through HIF1a,” Yaarit Adamovich, Benjamin Ladeuix, Marina Golik, Maarten P. Koeners and Gad Asher, Cell Metabolism (Oct. 20)
