Jet Lag Plays Favorites in Major League Baseball

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But it might not explain why the five AL East teams won 423 games last year.

By Nathan Collins

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The Phillies’ Alec Asher throws a pitch. (Photo by Mitchell Leff/Getty Images)

If you’ve ever flown cross-country, you know jet lag all too well: being unable to sleep at night, facing exhaustion in the afternoons. It can turn even the most cheerful vacation miserable. And it might affect professional baseball games, according to a new study.

Yes, jet lag appears to have an effect on Major League Baseball, Northwestern University researchers Alex Song, Thomas Severini, and Ravi Allada write today in Proceedings of the National Academy of Sciences, albeit in some surprising ways: Jet lag was most profoundly felt by East Coast teams returning home after series against teams in the West and Central divisions.

Song, Severini, and Allada reached that conclusion after a review of MLB games between 1992 and 2011—46,535 in all, including 4,919 in which either the home or away team had traveled across at least two time zones in the days leading up to a game. Then, they compiled some of baseball fans’ favorite statistics: wins and losses, runs scored, batting averages, on-base percentages, and slugging percentages (the total number of bases reached divided by the number of turns at bat).

The team broke their analysis down into four groups, based on whether the team actually doing the travel was at home or away—that is, whether the team was returning home to play a series or flying to another city—and whether they were traveling east or west.

As one might expect, traveling east was harder on teams than traveling west, but travel really only hurt home teams. In particular, jet-lagged teams traveling east to their home fields lost 3.5 percent more games—comparable to their home-field advantage of 3.9 percent. That travel was also harder on home teams’ slugging percentages, which dropped 1 percent after eastward trips. There were no such effects when traveling west.

Defense was a slightly different story, but eastward travel still made a difference: Jet-lagged home teams gave up about one home run every nine games, on average, while jet-lagged away teams gave up about one home run every 14 games. Again, there was no effect when traveling west.

The home-run results in particular suggest teams may want to change certain travel plans. “For instance, a starting pitcher scheduled for a game in which the team is jet lagged might travel to the game location a few days ahead of the team, to adjust to the new time zone,” the researchers write.

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