Hvis man går lidt tættere på kilden finder man:
This study had several limitations. First, a major limitation is ascertainment bias associated with participation in this brain donation program. Although the criteria for participation were based on exposure to repetitive head trauma rather than on clinical signs of brain trauma, public awareness of a possible link between repetitive head trauma and CTE may have motivated players and their families with symptoms and signs of brain injury to participate in this research. Therefore, caution must be used in interpreting the high frequency of CTE in this sample, and estimates of prevalence cannot be concluded or implied from this sample. Second, the VA-BU-CLF brain bank is not representative of the overall population of former players of American football; most players of American football have played only on youth or high school teams, but the majority of the brain bank donors in this study played at the college or professional level. Additionally, selection into brain banks is associated with dementia status, depression status, marital status, age, sex, race, and education. Third, this study lacked a comparison group that is representative of all individuals exposed to American football at the college or professional level, precluding estimation of the risk of participation in football and neuropathological outcomes.
http://jamanetwork.com/journals/jama/fulla...
Så selvom vi ikke kan konkludere ret meget om hvor farligt det er at spille NFL, er det en god indikator på at det er noget der skal undersøges dybere.
CNN kan slippe af sted med det, men jeg har lidt højere standarder til ing.dk ;)