The Reliability of Concussion History in Former Professional Football Players.
Kerr ZY, Marshall SW, Guskiewicz KM.
Med Sci Sports Exerc. 2011 Aug 12. [Epub ahead of print]
This past week the new MacArthur fellowships, popularly referred to as the “genius grants” were announced and among the recipients was Kevin Guskiewicz. Dr. Guskiewicz has “made major advances in the diagnosis, treatment, and prevention of sports-related concussions.” Unlike many funding opportunities this award is unique in that you must be anonymously nominated, show exceptional merit and promise in your work, and the award money can be used in any way to advance the individual’s work. We would like to take this opportunity to acknowledge and thank Dr. Guskiewicz for his hard work regarding concussions. With that in mind we’d like to acknowledge one of Dr. Guskiewicz’s most recent contributions to concussion research.
Often times, retrospective studies need to rely on the participant recalling whether they have experienced a certain injury or illness. Unfortunately, in concussion research the reliability (consistency) of reporting a history of concussions has never been evaluated and therefore it is unclear if data from these studies are biased (leaving room for people to question study findings). Therefore, Kerr et al studied the reliability of self-reported concussion history among a group of retired professional football players. In 2001, 2,536 retired professional football players completed a general health survey that inquired about previous health conditions including the number of concussions (their definition of concussion is in the paper) sustained during their professional football career and the medical conditions such as depression, Parkinson’s disease, and other pathologies (see some papers from this original survey: Guskiewicz et al 2005, Guskiewicz et al 2007). Several other health outcomes were also collected in 2001. In 2010, 899 of the participants that completed the survey in 2001 completed the survey again. The authors focused on the number of reported concussions during the athletes’ professional career and categorized the responses from both years as: 0 concussions, 1 to 2 concussions, 3 or more concussions. Reliability was determined on whether athletes fell into the same category in 2001 and 2010. 62% of participants reported the same number of concussions in both surveys, 31% reported more concussions during their professional careers in the 2010 survey, and 7% reported fewer concussions during their professional careers. Participants reporting a greater number of concussions in 2010 had a greater drop in mental health composite score between 2001 and 2010 (suggesting greater loss in mental health).
This study was an important step in helping to clarify the long-term consequences of concussions. Without reliability studies like this one, retrospective studies that suggest a link between previous concussions and long-term neurocognitive conditions can be questioned. The authors believe that the current reliability data suggests that previously reported associations between history of concussions and neurocognitive conditions may still be accurate since most participants accurately report the number of concussions. The authors note that one reason for the increased reporting of concussions may be due to the elevated media coverage of concussions over the past 10 to 15 years. From a clinical point of view, this study suggest that data on self-reported concussion history from large cohort studies may be reliable but at an individual level (e.g., in the clinic) it might not be accurate enough to rely on because almost 40% of retired athletes changed the number of concussions they reported. The authors note that another important step will be to validate self-reported history of concussions with verifiable concussion data. Studies like this one and Dr. Guskiewicz’s previous research has helped raise awareness and improve our understanding of concussions and their long-term implications. Once again, we wish him continued success and look forward to seeing more research from him.
Written by: Jeffrey B. Driban
Reviewed by: Steven Thomas
Kerr ZY, Marshall SW, & Guskiewicz KM (2011). The Reliability of Concussion History in Former Professional Football Players. Medicine and Science in Sports and Exercise PMID: 21857370
Congratulations to Dr. Guskiewicz on his MacArthur Fellowship grant. This is not only a personal achievement, but also a victory for the whole Sports Medicine community and an inspiration to future researchers
Through my review of the literature, I would agree that self-reported history is one major limitation to current concussion research. The above study is unique and provides us with information that was largely unknown until this point. It is astounding that 31.4% of former professional football players included in this study reported having had more concussions that they had reported 9 years prior. It is also interesting that these same participants showed deficits on the second administration of physical and mental health examinations. Overall, the moderate reliability results of this study will help facilitate future research on the long-term effects of concussion.
Due to the high number or unreported and undiagnosed concussions, I still have my reservations about the reliability of self-reported concussion history. There does not appear to be a clear solution to combat these issues, but more studies like the Kerr and Guskiewicz study above will lead us in the right direction.
Erica: Great comments. Thanks! As the authors noted, the issue won't be completely resolved until we can validate self-reported history of concussions with verifiable concussion data. This hopefully highlights for the new investigators (as well as experienced investigators) that we have a huge need in sports medicine for well designed long-term prospective studies.
The research model that Guskiewicz and other concussion researchers have laid out can be a good example to other areas of sports medicine research about how to proceed. For example, research evaluating long-term risks of developing osteoarthritis after joint trauma could benefit from more long-term epidemiology data, evaluations of early risk factors, etc.