Baseball, America’s pastime, has been part of the nation’s culture for more than 140 years—we go to games, watch games on TV, and teach our kids to play. Fans can get obsessive about statistics, figuring out various ways of measuring a player’s probability of contributing to a win.

They should start checking the travel schedule. A recent article published in PNAS indicates that jet lag can be an important factor in baseball. Jet lag seems to hinder home-team offensive performance and negatively affect defensive performance for both home and away teams. These results showed the surprisingly strong effect of disrupted circadian rhythms on elite athletic performance.

The scientists behind this study analyzed 20 years of Major League Baseball (MLB) data, including more than 46,000 games. They were looking for instances of teams experiencing at least two hours of jet lag, as represented by the numbers of time zones they crossed while traveling just before games. They also accounted for important potential confounders, such as home-field advantage and direction of travel (eastward or westward). Previous studies have shown that it is easier to adjust to westward travel than eastward travel.