of deaths from suicide, accidents, cardiovascular or cerebrovascular disease, or malignancies were observed. In addition, the overall prevalence of posttraumatic epilepsy was 28% in the consecutive series and ranged from 7% in those with uncomplicated injury and PTA of less than a week to 61% in those with complicated injury (compression and traumatic or surgical penetration). An increase in the prevalence of seizures was seen with length of PTA (uncomplicated) and with duration of coma (complicated and uncomplicated).
Concussions are relatively common in people who participate in contact sports, so studies of such people afford a unique opportunity to assess the short-term and long-term consequences of head injury. It is estimated that over 300,000 sports-related concussions occur each year in the United States (Guskiewicz et al., 2005). The studies discussed below focus on the long-term health outcomes related to sports-related TBI. Although not all the studies include large cohorts, the committee believed that it was important to discuss the strengths and limitations of studies of sports-related TBI. Contact sports provide a useful laboratory for assessing the influence of recurring mild TBI on such health outcomes as dementia and Alzheimer disease. One advantage of studies of sports-related TBI is that there is a large population to draw from. A major limitation, however, is that many studies are based on self-reported measures. For instance, participants’ TBIs are commonly ascertained by asking subjects whether they recall having had a concussion or, less commonly, whether they had a clinical diagnosis of a head injury.
American football is a “collision sport” that is widely known for causing a variety of injuries, including cerebral concussions. It has been reported that a large percentage of professional football players have sustained at least one concussion during their careers (Guskiewicz et al., 2005).
Guskiewicz and colleagues (2005, 2007) studied the association of recurrent concussions sustained and long-term health outcomes, including mild cognitive impairment and risk of depression in retired professional football players. The authors originally sent a survey to all 3,683 living members of the National Football League Retired Players Association. The survey instrument included questions about musculoskeletal, cardiovascular, and neurologic conditions experienced during and after the football career. Questions were also asked about the number of concussions sustained during the football career and the presence of such health conditions as depression, Parkinson disease, Alzheimer disease, and schizophrenia (Guskiewicz et al., 2005). Concussion history was based on players’ recall of injury events, and concussion was defined as “injury resulting from a blow to the head that caused an alteration in mental status and one or more of the following symptoms: headache, nausea, vomiting, dizziness/balance problems, fatigue, trouble sleeping, drowsiness, sensitivity to light or noise, blurred vision, difficulty remembering, and difficulty concentrating.” The mailed questionnaire included the SF-36 Measurement Model for Functional Assessment of Health and Well-Being to assess daily-living functioning. A physical-health composite score was calculated. The authors sent out a second questionnaire to a subset of 1,754 of the original population that included questions on memory and issues related to mild cognitive impairment.