Monday, December 2, 2013

Do sports concussions really cause chronic traumatic encephalopathy?

MAYWOOD, Ill. –  It’s been widely reported that football and other contact sports increase the risk of a debilitating neurological condition called chronic traumatic encephalopathy (CTE).

But in the journal Neuropsychology Review, researchers are reporting only limited evidence showing a link between sports concussions and an increased risk of late-life cognitive and neuropsychiatric impairments.

Christopher Randolph, PhD, Loyola University Chicago Stritch School of Medicine professor in the Department of Neurology, is a co-author of the paper. First author is Stella Karantzoulis, PhD, of New York University School of Medicine.

CTE is believed to be the cause of behavioral symptoms including irritability, anger, aggression, depression and suicidality; and cognitive symptoms including impaired learning, memory, language, information-processing speed, and executive functioning. CTE is said to be linked to concussions and characterized by the buildup of abnormal substances in the brain called tau proteins.

But so far there is only limited evidence to support this CTE theory, Karantzoulis and Randolph write. These are among the limitations of the evidence:

  • So far CTE cases have been reported following the autopsies of athletes’ brains that were donated from families concerned about the players’ cognitive and behavioral symptoms before dying. But such non-random “samples of convenience” can bias findings because the samples may not be representative of the entire population of retired players.
  • The largest epidemiological study of retired NFL athletes, which included 3,439 players, found that suicide rates were actually substantially lower among these athletes than among the general population. “Given that suicidality is described as a key feature of CTE, this finding is difficult to reconcile with the high rates of CTE that have been speculated to occur in these retired athletes . . . ,” Karantzoulis and Randolph write. “It is likely that there are a diverse set of risk factors for suicidality (e.g. life stress, financial difficulty, depression, chronic pain, drug abuse) in retired athletes . . ."
  • Two previous studies, including one by Randolph and colleagues, examined symptoms of retired NFL players who had mild cognitive impairment, a precursor to Alzheimer’s disease. In both studies, symptoms seen in the retired players were virtually the same as those observed in non-athletes diagnosed with mild cognitive impairment. These findings cast doubt on the notion that CTE is a novel condition unique to athletes who have experienced concussions.
  • The presence of abnormal tau proteins in the brain may not be a reliable indicator of CTE. For example, various case studies have found that between 20 percent and 50 percent of subjects who had abnormal tau deposits nevertheless did not have any symptoms. “Older persons without dementia can accumulate Alzheimer’s disease pathology (including tau deposition) without any associated cognitive or clinical symptoms,” Karantzoulis and Randolph write. “The actual clinical significance of ‘abnormal’ tau deposition in the brains of retired athletes therefore remains unclear."

The authors detail how CTE originally was identified in 1928 as “punch drunk” syndrome in boxers. There is a striking parallel between the controversy over CTE today and punch drunk syndrome decades ago. In 1965, for example, a skeptic argued that punch drunk syndrome symptoms seen in boxers could have been due to alcoholism and venereal diseases, which were common in boxers at the time.

“One cannot deny that boxing and other contact sports can potentially result in some type of injury to the brain,” Karantzoulis and Randolph write. “There currently are no carefully controlled data, however, to indicate a definitive association between sport-related concussion and increased risk for late-life cognitive and neuropsychiatric impairment of any form."

The authors say more rigorous and definitive studies are needed than the case reports and samples of convenience that have been done to date.

The study is titled “Modern Chronic Traumatic Encephalopathy in Retired Athletes: What is the Evidence?"

Randolph also is a Loyola University Medical Center clinical neuropsychologist.

About Loyola University Health System

Loyola University Health System (LUHS) is part 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. Loyola University Medical Center’s campus is conveniently located in Maywood, 13 miles west of Chicago’s Loop and 8 miles east of Oak Brook, Ill. At 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 Loyola University Chicago Stritch School of Medicine, Loyola University Chicago 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.

Trinity Health is a national Catholic health system with an enduring legacy and a steadfast mission to be a transforming and healing presence within the communities we serve. Trinity is committed to being a people-centered health care system that enables better health, better care and lower costs. Trinity Health has 88 hospitals and hundreds of continuing care facilities, home care agencies and outpatient centers in 21 states and 119,000 employees.