Lonely Planet Writer

Why is jet lag worse when travelling east? Science provides some answers

Anyone who regularly travels across time zones will probably have noticed a strange feature of jet lag … that the effects travelling east almost always seem much worse.

Jet lag: science reveals why it's worse when flying east.
Jet lag: science reveals why it’s worse when flying east. Image by Getty Images

Jet lag has been studied in laboratories for decades but measuring how much impact it has on real people in real life has been more difficult. In a new study however, scientists came up with a novel method of measuring just how much it affects people. They examined twenty years of games in US Major League Baseball (MLB) to see how frequent travel affected the performance of players.

Study examined the effects of jet lag on baseball players
Study examined the effects of jet lag on baseball players Image by Getty

The stars of US baseball travel constantly back and forth across North America and regularly deal with long flights and time changes of three hours. An incredibly detailed analysis of games – who scored what, how well pitchers threw, home and away advantage – did find one relatively consistent theme.

Most of the significant jet lag effects were stronger for eastward travel when compared to westward, according to the Northwestern University study. The science behind it is based on the natural circadian rhythms of human beings. At its simplest, people have evolved to perform best on a daily cycle that runs to just over twenty-four hours.

Researchers studied the effect on air passengers travelling east.
Researchers studied the effect on air passengers travelling east. Image by Getty

If we travel west and gain a few extra hours in the day, our bodies are better able to cope than when we go the other direction and lose hours.Scientists reckon that when we travel west, we need less than a day to readjust for each hour of time difference. However, on eastbound travel – we need almost a day and a half to get back in sync.

The effect was pronounced in the baseball study, with significant under-performance by teams dealing with changing time zones. Dr Ravi Allada, a circadian rhythms expert, said: ‘The negative effects of jet lag we found are subtle, but they are detectable and significant. And they happen on both offense and defense and for both home and away teams.’

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