The study, conducted by University of North Carolina at Chapel Hill researchers and colleagues, found that retired National Football League players also faced a 37 percent higher risk of Alzheimer's than other U. S. males of the same age.
A report on the findings, which are being presented at a Congress of Neurosurgery scientific meeting in Boston today (Oct. 10), appears in the October issue of the journal Neurosurgery. Lead authors are Drs. Kevin M. Guskiewicz, professor of exercise and sport science in the UNC College of Arts and Sciences, and Stephen W. Marshall, associate professor of epidemiology at the UNC School of Public Health and of orthopaedics at the UNC School of Medicine. Guskiewicz also chairs the exercise and sport science department, directs the university's Center for the Study of Retired Athletes and Sports Medicine Research Laboratory and holds a joint appointment in othopaedics.
"In this unique study, we had some very interesting findings," Guskiewicz said. "Our data suggest that a history of recurrent concussions and probably sub-concussive contacts to the head may be risk factors for the expression of late-life memory impairment, mild cognitive impairment and earlier expression of Alzheimer's disease. Research like this is important since more than 300,000 sport-related concussions, many of which are recurrent injuries, occur annually in the U.S. and more than 1.2 million Americans suffer head injury each year."
The study involved surveying by mail 3,683 retired professional football players who belonged to the NFL Retired Player's Association about their overall health and analyzing the results.
Of those, 2,552 returned questionnaires or had their spouses or other close relatives do so for about a 70 percent response rate. Players averaged almost 54 years old and had an average professional career spanning 6.6 years.
Researchers then surveyed a subset of 758 players aged 50 and older and asked more detailed questions about concussions and diagnosed dementia-related impairments. Spouses and close relatives also participated and assisted in confirming responses provided by the retired players.
"When considering prevalence of previous concussions, 1,513, or 60.8 percent, of the retired players reported having sustained at least one concussion during their professional playing career, and 597, or 24 percent, reported sustaining three or more concussions," Guskiewicz said.
Among retired players who sustained a concussion during their professional careers, more than half reported experiencing loss of consciousness or memory loss from at least one of their concussions, he said.
"We asked the retired players for their subjective assessment of the long-term consequences of their injuries," Guskiewicz said. "Of the retirees who sustained at least one concussion, 266, or 17.6 percent, reported that they perceived the injury to have had a permanent effect on their thinking and memory skills as they have gotten older. The findings showing a relationship between diagnosed mild cognitive impairment and history of concussions -- three or more -- suggest that a true memory effect is present."
Retired players with three or more concussions had a five-fold greater chance of having been diagnosed with mild cognitive impairment and a three-fold prevalence of reported significant memory problems compared to those players without a history of concussion, he said. Physicians had diagnosed 33 players with Alzheimer's. The higher prevalence of the memory-destroying disease was more noticeable in the younger age groups -- those below age 70 than in those over that age.
Co-authors of the report are Dr. Julian Bailes of the West Virginia University School of Medicine, Dr. Michael McCrea Waukesha Memorial Hospital and the Medical College of Wisconsin in Milwaukee, Dr. Robert C. Cantu of Emerson Hospital in Concord, Mass., and Brigham and Women's Hospital in Boston, Dr. Christopher Randolph of the Chicago Neurological Institute and Loyola University Medical School in Maywood, Ill., and Barry D. Jordan of Burke Rehabilitation Hospital in White Plains, N.Y.
The study's chief limitation was that it was based on self-reported answers to the health questions, and the accuracy of remembering memory problems could not be verified completely.
"Future prospective studies should implement genetic testing since genes are known to affect memory," Guskiewicz said. "Also, there needs to be more rigorous diagnostic criteria, historical documentation of injuries and periodic evaluations such as neurophysiologic testing and functional neuroimaging to clarify the effects of concussion on lifetime risk of dementia or other neurologic disorders."
Note: Guskiewicz can be reached through Mike Smith at (919) 962-0017 or Amy Matthews at (919) 962-5744 or via email at firstname.lastname@example.org. Marshall can be reached at (919) 966-1320 or email@example.com.
News Services contact: David Williamson, (919) 962-8596
By DAVID WILLIAMSON
UNC News Services