TABLE 1.
Association Between Altitude and Concussions Among All United States High School Sports Combineda
| Dichotomous Altitude, ft | Altitude in Quartiles, ft | |||||
|---|---|---|---|---|---|---|
| 0-600 | ≥601 | 0-200 | 201-600 | 601-935 | ≥936 | |
| Total | ||||||
| No. of concussions | 3207 | 2729 | 1673 | 1534 | 1407 | 1322 |
| No. of AEs | 9,748,551 | 10,870,364 | 5,658,239 | 4,090,312 | 5,476,019 | 5,394,345 |
| Rate per 10,000 AEs | 3.29 | 2.51 | 2.96 | 3.75 | 2.57 | 2.45 |
| RR | 1.31 | Referent category | 1.21 | 1.53 | 1.05 | Referent category |
| 95% CI | 1.25-1.38 | 1.12-1.30 | 1.42-1.65 | 0.97-1.13 | ||
| P value | <.001 | <.001 | <.001 | .22 | ||
| Competition | ||||||
| No. of concussions | 2110 | 1781 | 1121 | 989 | 919 | 862 |
| No. of AEs | 2,588,783 | 2,868,496 | 1,466,303 | 1,122,481 | 1,444,549 | 1,423,947 |
| Rate per 10,000 AEs | 8.15 | 6.21 | 7.65 | 8.81 | 6.36 | 6.05 |
| RR | 1.31 | Referent | 1.26 | 1.46 | 1.05 | Referent |
| 95% CI | 1.23-1.40 | 1.16-1.38 | 1.33-1.59 | 0.96-1.15 | ||
| P value | <.001 | <.001 | <.001 | .29 | ||
| Practice | ||||||
| No. of concussions | 1097 | 948 | 552 | 545 | 488 | 460 |
| No. of AEs | 7,159,767 | 8,001,868 | 4,191,936 | 2,967,831 | 4,031,470 | 3,970,398 |
| Rate per 10,000 AEs | 1.53 | 1.18 | 1.32 | 1.84 | 1.21 | 1.16 |
| RR | 1.29 | Referent | 1.14 | 1.59 | 1.04 | Referent |
| 95% CI | 1.19-1.41 | 1.00-1.29 | 1.40-1.79 | 0.92-1.19 | ||
| P value | <.001 | .04 | <.001 | .50 | ||
aFrom the National High School Sports-Related Injury Surveillance System, United States, 2005-2006 through 2011-2012. AE, athlete exposure; CI, confidence interval; RR, rate ratio.