A Preliminary Study of Early-Onset Dementia of Former Professional Football and Hockey Players.

The sample was small and analysed 22 contact athletes and 21 controls, although 27 contact athletes and 24 controls volunteered. Recruitment through alumni associations and clubs was a convenience sample, and the authors worried that volunteers may have been athletes who were already concerned about their mental state. Some likely non-participants were excluded because they had health conditions or public roles, which may make the sample less representative. The control group were currently active master athletes, so they may have had better health and fitness than retired contact athletes. Contact athletes had higher body-mass-index, less education, more chronic pain, more sleep disturbance, and less exercise, and the authors note these differences could bias toward lower cognitive scores in the contact group. Concussion history was not analysed because retrospective recall of repeated head blows decades earlier was judged too inaccurate. The study did not adjust for multiple comparisons, which increased the likelihood of finding significant differences. CTE cannot be diagnosed in living people by this study, because post-mortem analysis is currently the only definite diagnosis. This is an overview paper; detailed cognitive, executive, mental health, and imaging results are reported in accompanying articles. The contact athletes were alive and volunteered for assessment, while prior CTE samples came from brains donated by families who thought something was wrong, so the samples are not comparable.

Research support is listed as NIH extramural and non-U.S. government. Robert Zivadinov received personal compensation from EMD Serono, Novartis, Celgene, Genentech, Claret Medical and Sanofi-Genzyme for speaking and consultant fees, and received research support from Biogen Idec, Teva Pharmaceuticals, Sanofi-Genzyme, Novartis, Claret Medical and Coherus-Intekrin. Other investigators reported no conflicts.

Do not conclude that contact sport athletes are free of CTE risk or that dementia is not a concern. The study had 22 contact athletes and 21 controls, volunteers were recruited through alumni associations, and the authors say it does not argue against the existence of CTE.