What Eastward Travel Costs You, According to the NBA

This study used a genuinely large real-world dataset, over eleven thousand professional basketball games across a decade, to ask whether the direction of recent travel actually shows up in performance. It did, but with an important asymmetry: home teams that had recently travelled eastward, shortening their body clock's day, showed a measurably reduced chance of winning, fewer points scored relative to their opponent, and fewer rebounds, with the effect growing larger the more hours of eastward jet lag involved. Westward travel, by contrast, showed no equivalent performance cost. This lines up with well-established circadian biology: it is generally harder for the body clock to move earlier, as eastward travel demands, than later.

Elite athletes obviously aren't a perfect stand-in for everyone, and the study measures game outcomes rather than sleep or biology directly, inferring jet lag from travel schedules rather than measuring each player's circadian phase. But the scale of the dataset, ten full seasons, makes this a rare demonstration of jet lag's cost playing out in real, high-stakes performance rather than a lab proxy, and it offers a concrete, memorable rule of thumb: eastward travel, particularly with little recovery time, is the direction to plan around.