- Note that this study, which was not a randomly selected cross-section, suggests that cognitive deficits and depression appear to be more common in retired NFL players compared with healthy controls.
- These cognitive deficits were correlated with disrupted white matter and changes in regional cerebral blood flow.
Among a cohort of 34 former National Football League players, neurocognitive testing revealed difficulties in word finding, naming, and episodic and verbal memory (P<0.001 for all), according to John Hart, Jr., MD, of the University of Texas at Dallas, and colleagues.
And in a subgroup of these players who underwent specialized brain imaging, significant differences were detected in total white matter lesion volume (8.13 mL versus 2.38 mL, P=0.04) and deep lesion volume (1.01 mL versus 0.22 mL, P=0.02) compared with healthy controls, the researchers reported online in JAMA Neurology.
"Disrupted white matter integrity appears to represent a potentially important biomarker for neurobehavioral impairment," they observed.
There has been a good deal of interest in the long-term neurocognitive effects of concussions among athletes, particularly following the widely publicized suicides of some prominent players such as Dave Duerson who were diagnosed on autopsy as having injury-related chronic traumatic encephalopathy (CTE).
And while data on the pathophysiology and long-term sequelae of mild traumatic brain injury have begun to accumulate, studies have not yet systematically examined the relation between cognitive and mood abnormalities and neuroimaging findings in living older athletes.
Therefore, Hart and colleagues recruited 34 former professional football players whose mean age was 62 and who had experienced an average of four concussions in the past.
Neurocognitive assessments determined that eight had mild cognitive impairment, four had fixed cognitive deficits, and two had dementia.
Those 14 together were classified as having cognitive impairments.
In addition, eight were diagnosed with depression, with three having both depression and cognitive impairment.
A total of 26 of the former players underwent various neuroimaging studies.
Along with measurement of white matter lesion volumes, participants also had diffusion tensor imaging to estimate fractional anisotropy, which reflects factors such as axonal diameter and nerve fiber density.
Compared with healthy matched controls, the former players had decreases in fractional anisotropy throughout the frontal and parietal areas, as well as in the left temporal lobe and the corpus callosum.
Among the former athletes, reduced fractional anisotropy was seen for both those having cognitive impairments and those with depression, the researchers noted.
Further imaging using arterial spin labeling revealed increased blood flow in certain regions among the impaired former athletes, including the superior temporal gyrus and the left inferior parietal lobe.
Those areas of the brain "are thought to play important roles in naming and word finding, and the increase in blood flow in the impaired players may reflect compensatory responses to impaired function in other regions," Hart and colleagues explained.
In addition, blood flow and metabolic activity were reduced in the impaired players in other areas such as the left temporal pole, which also plays an important role in verbal ability.
"Our findings suggest that a dynamic process underlies dysfunction in these players as they age and that their deficits do not simply reflect the static effects of previous damage," the researchers wrote.
They noted that the number of men in their cohort with dementia was similar to that in the age-matched wider population, whereas other studies of aging athletes have found higher numbers with dementia. This might be explained by the sample, which consisted of volunteers who may have been particularly motivated to participate in such a study -- "although bias is typically toward more, not fewer, with impairment," the researchers wrote.
Conversely, the number specifically with mild cognitive impairment was higher than would be expected, and those participants will be followed to determine their clinical course over time.
The prevalence of depression, at 24%, also was somewhat higher than the 15% usually reported for men of that age, which emphasizes the importance of screening older athletes for depression and other cognitive-behavioral problems, Hart and colleagues noted.
In addition, prospective studies will be needed to more fully elucidate the development and clinical features of depression among retired athletes, and particularly in relation to the late, severe manifestations associated with chronic traumatic encephalopathy.
In an editorial accompanying the study, Ramon Diaz-Arrastia, MD, PhD, and Daniel Perl, MD, of the Uniformed Services University of the Health Sciences in Bethesda, Md., also called for more epidemiologic data on the incidence on chronic traumatic encephalopathy and risk factors.
"Because the symptoms of CTE, such as irritability, depression, and cognitive problems, are protean and nonspecific, biomarkers and neuroimaging to complement the clinical examination will likely be essential and will improve the accuracy of the diagnosis during the lifetime of the individual and will be used to follow the natural history of the illness," Diaz-Arrastia and Perl stated.