But a study by a Loyola University Medical Center neuropsychologist has found little evidence that CTE actually exists.
“There has not yet been one controlled epidemiological study looking at the risk of late-life cognitive impairment in any collision sport, including boxing, American football or other sports involving repetitive head trauma,” said Christopher Randolph, PhD, in the journal Current Sports Medicine Reports.
CTE is said to be the cause of behavioral symptoms such as anger, aggression and suicidality, and cognitive symptoms such as impaired learning and memory problems. CTE is thought to be linked to concussions and characterized by the buildup of abnormal substances in the brain called tau proteins.
A 2005 study, co-authored by Randolph, reported that rates of mild cognitive impairment among retired NFL players seemed to be higher than that of the general population. But Randolph noted there were no controls in this study and results may have been subject to reporting bias.
A more recent study of retired NFL players found that rates of Alzheimer’s disease and amyotrophic lateral sclerosis (Lou Gehrig’s disease) were higher than that of the general population. But this may be due to the fact that the NFL players had lower overall mortality rates from heart disease and other causes. Since they lived longer, the players naturally would be more likely to get age-related diseases such as Alzheimer’s disease.
In addition to having much lower overall mortality rates than the general population, retired NFL players are only 40 percent as likely to die of suicide as men in the general population, according to a 2012 study. It is difficult to reconcile this finding with the high rate of suicide that is said to be a key feature of CTE.
“Overall, although retired NFL players have been the focus of more attention into the potential late-life neurological consequences of repetitive head trauma than athletes in any other sport, the risks for these retirees remains largely hypothetical,” Randolph wrote.
The list of symptoms that have been associated with CTE “is so broad as to be essentially meaningless in any attempt to define a clinical syndrome,” Randolph wrote. Some of these symptoms are found in the healthy population, while other symptoms have been observed in a variety of neurological diseases. The broad range of CTE symptoms includes attention problems, paranoia, executive impairment, suicidality, memory loss, language impairment, visuospatial impairment, apathy, gait disturbance, dysarthria (speech disorder), Parkinsonism, Post-Traumatic Stress Disorder, headache, depression, impulsivity, explosivity and aggression.
Loyola University Health System (LUHS) is a member of Trinity Health. Based in the western suburbs of Chicago, LUHS is a quaternary care system with a 61-acre main medical center campus, the 36-acre Gottlieb Memorial Hospital campus and more than 30 primary and specialty care facilities in Cook, Will and DuPage counties. The medical center campus is conveniently located in Maywood, 13 miles west of the Chicago Loop and 8 miles east of Oak Brook, Ill. The heart of the medical center campus is a 559-licensed-bed hospital that houses a Level 1 Trauma Center, a Burn Center and the Ronald McDonald® Children’s Hospital of Loyola University Medical Center. Also on campus are the Cardinal Bernardin Cancer Center, Loyola Outpatient Center, Center for Heart & Vascular Medicine and Loyola Oral Health Center as well as the LUC Stritch School of Medicine, the LUC Marcella Niehoff School of Nursing and the Loyola Center for Fitness. Loyola’s Gottlieb campus in Melrose Park includes the 255-licensed-bed community hospital, the Professional Office Building housing 150 private practice clinics, the Adult Day Care, the Gottlieb Center for Fitness, Loyola Center for Metabolic Surgery and Bariatric Care and the Loyola Cancer Care & Research at the Marjorie G. Weinberg Cancer Center at Melrose Park.