Examining Circadian Disadvantages in the National Basketball Association's (NBA) Playoffs

Introduction: Prior research on travel in the National Basketball Association’s (NBA) regular season has shown that teams journeying west relative to their home base face circadian disadvantages for evening games, while those traveling east have advantages. The current study extends previous research by examining these effects within the NBA playoffs. We hypothesized that teams would have a greater circadian advantage during eastward compared to westward travel. Methods: In 2013, the NBA implemented a 7-game series playoff structure, in which teams play an alternating home/away 2-2-1-1-1 format for the Finals. Data for all 499 postseason games played during the 2013-14 to 2018-2019 seasons were collected from Basketball-Reference and FiveThirtyEight. We investigated the impact of direction of travel based on home base city (same time zone, westward, eastward) and time zones traveled on actual game outcomes, Elo rating differences (i.e., a team quality metric based on wins and losses), Elo predicted win probability, and team scoring for visiting teams. Results: Teams had lower Elo predicted win probabilities following 3-hour westward than same time zone and all eastward travel, while 3-hour eastward travel related to higher probabilities of winning compared to same time zone and all westward travel (p < .02, d > .95). Teams travelling westward with 2-hour time changes lost significantly more games than those experiencing 1-hour westward (p = .04, OR = 2.45), 1-hour eastward (p = .05, OR = 2.34), and 3-hour eastward changes (p = .02, OR = 4.68). Scoring was significantly higher following eastward travel compared to both westward (p = .001, d = 0.60) and same time zone travel (p = .003, d = 0.44). There were no statistically clear differences in team quality based on overall direction of travel or number of time zones traveled, and game outcomes based on direction of travel (p > .05). Conclusion: Overall direction of travel was related to team scoring, while number of time zones traveled was associated with Elo predicted win probability and game outcomes. Generally, teams travelling eastward and within the same time zone gained an advantage over those travelling westward. Adjustment to travel and time zone changes appear to influence certain aspects of in-game performances and outcomes in the NBA playoffs.