Elite athletes cross time zones constantly, and jet lag is not symmetrical: flying east shortens the day and is harder on the body clock than flying west. If that physiology reaches performance, the direction of travel should matter and not just the distance. So ten seasons of NBA data, 11,481 games, were analyzed with home and away games separated and accounted for.
Eastward travel hurt home teams, westward did not. Among home teams, was associated with reduced winning, a change of about 6 percent. The came in 1.29 points lower, the rebound differential 1.29 rebounds lower, and the differential 1.2 percent lower. The effect scaled with the lag: two hours of eastward jet lag cost 4.53 points against 0.72 for one hour.
Elite athletes are often required to travel across time zones, which produces frequent jet lag. The physiology is asymmetric: the human circadian clock runs a little longer than a day, so westward travel delays it comfortably while eastward travel demands an advance that is harder to achieve. If performance follows the clock, direction should matter.
Ten seasons comprising 11,481 games of NBA data, from the 2011 to 2012 season through 2020 to 2021, were analyzed using multi-level mixed models. Jet lag direction was the single fixed factor at three levels, eastward, westward and none, with team, opponent and game time as random factors. Predicted circadian resynchronization rate was accounted for, and home and away games analyzed separately.
Among home teams, eastward but not westward jet lag was associated with reduced winning, a change of about 6 percent at a marginal P value of 0.051. It also went with a points differential lower by 1.29 points and a rebound differential lower by 1.29 rebounds. The effective field goal percentage differential was lower by 1.2 percent.
The dose response strengthens it. As the magnitude of eastward jet lag increased, home team points differential decreased further, with two hours of lag costing 4.53 points against 0.72 points for one hour. Read the design for what it is. This is archival observational data in which travel direction arrives bundled with schedule and opponent, reduced by the random factors rather than eliminated, and the headline winning result is only marginal.
wat. NBA teams playing at home after flying east gave up more than a point of scoring margin, and flying west cost them nothing.
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The asymmetry is the evidence. A result that appeared for both travel directions could be fatigue or disruption in general, while one that appears only going east points at the circadian clock specifically.
How do we know?
Leota and colleagues analyzed 11,481 NBA games across ten regular seasons using multi-level mixed models. Jet lag direction was the fixed factor, with team, opponent and game time as random factors, and predicted circadian resynchronization rate accounted for.
What is still unknown
Observational archival data, so travel direction travels with schedule, opponent quality and much else, which the random factors reduce rather than remove. The reduced-winning result was marginal at a P value of 0.051.
Learn something?
Where to next
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