Lit review: Altitude provides no protection against concussion. Case closed?

Contrary to popular perception, Denver Broncos players have no less chance of getting concussions on their mile-high home field than when they play in Miami, Los Angeles or any other field that’s not at elevated altitude.

In fact, according to the authors of a meta-analysis posted online Sept. 6 in JAMA Neurology, the notion that higher altitude reduces concussion incidence in athletes is based on nothing more than “myth.”

Gerald Zavorsky, PhD, of Georgia State University in Atlanta and James Smoliga, DVM, PhD, of High Point University in North Carolina, note in their introduction that various observers have suggested a higher altitude may be concussion-protective because it increases cerebral blood flow, swelling the brain such that it doesn’t knock around inside the skull.

The authors arrived at their contrary conclusion by reviewing the relevant literature after searching PubMed.gov using the terms altitude or elevation and concussion or concussions.

Zavorsky and Smoliga found 59 published studies. For their meta-analysis, they narrowed the field to three retrospective studies—one each based on injury data from the NFL, Division I collegiate football and the National High School Sports Related Injury Surveillance System.

Their key finding, in their words:

“[T]here is no physiologic basis for an altitude less than approximately 2,200 meters (about 1.4 miles) influencing concussion risk, and this meta-analysis of nearly 5 million data points demonstrates that there is no clinically relevant association between altitude and concussion risk. Likewise, sports protective equipment meant to replicate the effects of altitude are not scientifically justified.”

Zavorsky and Smoliga take their conclusion even further, stating that the altitude-concussion hypothesis deserves no more investigation.  

“Further research on this issue,” they write, “will simply divert resources from more clinically effective research aimed at identifying modifiable risk factors for concussion, developing scientifically sound technologies that improve athlete safety, and improving acute and long-term management of sports-related head injuries.”

Some have already challenged the pair’s certainty. 

“The idea that three retrospective studies answer all the questions to the point where there is not more work to be done is, I think, a risky conclusion to an otherwise methodologically well-performed study,” Steven DeKosky, MD, of the University of Florida told MedPage Today.