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Affiliation
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Binney Research, Analytics, and Sports Services, LLC , Atlanta , GA. |
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Abstract
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In Volume 47, Issue 3 of this journal, Baker et al1 report an analysis of National Football League (NFL) injuries that occur on Thursday nights versus Sundays or Mondays. Thursday games are used as a proxy for short rest as the vast majority of games occur on Sundays. The authors sought to investigate whether shorter rest was associated with a higher injury rate. I wish to briefly address two issues with this paper.
First, and most importantly, while their conclusions that Thursday games are not associated with higher reported injury rates are correct2, the primary data point they report to support their findings – an injury rate ratio – does not pass the eye test. The authors report injury rates of 6,072 per 1,000 athletic exposures for Thursday night games and 7,598 per 1,000 athletic exposures for Sunday and Monday games. They also report a rate ratio – which they incorrectly term a “relative risk” – of 0.97 (95% confidence interval 0.95-0.98). One does not even need a calculator to see this is incorrect. 6,072/7,598 = 0.80, not 0.97. The 95% confidence interval around this rate ratio of 0.80 is 0.72-0.88.
I respectfully request a correction be issued and the paper be amended immediately.
Second, it is also worth noting that there is an explanation for why we might observe a lower reported injury rate on Thursdays even though it is implausible that shorter rest exerts a protective effect. It is a quirk of the way the timing of NFL injury reports work.2 Teams typically issue their first injury reports on Wednesday of each week: two days after a Sunday game but five days after a Thursday game. Any injury that resolves to the point the player can fully practice in that 3-6 day period would not be reported if it occurred on a Thursday but would be reported if it occurred on a Sunday. If 20 percent of reportable injuries resolve in that period, that would fully explain the lower Thursday injury rate.
References
1. Baker HP, Young-Hoon Lee K, Dayton SR, Terry M, Tjong VK. Thursday Night Football’s impact on all-cause injuries in NFL players during 2012 – 2017. The Physician and Sportsmedicine. 2019;47(3):350-352.
2. Binney ZO. Do Thursday Games Cause More Injuries? 2017; https://www.footballoutsiders.com/stat-analysis/2017/do-thursday-games-cause-more-injuries. Accessed September 16, 2019.
Keywords: American football
Language: en |