If you catch a cold while flying, should you blame the cramped cabin and recycled air on board? Maybe not. A new study of elite athletes that found that how far you travel plays a big part in making you sick.
Researchers followed over 200 elite rugby players from South Africa and New Zealand for 16 weeks. Those who traveled more than five time zones were two to three times to come down with some kind of illness than players who stayed closer to home.
Almost a third of the illnesses were respiratory infections, followed by ones related to the digestive system, and the skin and soft tissues.
In the study, published in the British Journal of Sports Medicine, researchers ruled out the planes or the stress of travel as the cause of illness during long-distance travel. Athletes who traveled more than five time zones had an increased risk of illness, but their health improved when they returned home.
“Changes in air pollution, temperature, allergens, humidity, altitude as well as different food, germs and culture could all contribute to illness when arriving in a distant destination,” Martin Schwellnus, one of the paper’s authors, told BBC News.
The researchers caution that, because the study was done with elite athletes during a busy rugby season, the results may not apply to infrequent travelers. Other studies of adults and children traveling long-distance, though, have shown similar results.
As a precaution, buy and use hand sanitizer during your next trip across multiple times zones—and get as much rest as you can before and during your trip.