Cases and controls were both about 60 years of age. The affected players had significantly higher scores on the Hamilton Rating Scale for Depression (8 versus 0) than controls, and also showed a trend toward lower scores on the Mini-Mental State Examination, which evaluates cognitive impairment.
Higher signals for tau binding were seen in a number of subcortical regions in cases compared with controls. The researchers explained that this pattern of findings was different from that seen in patients with cognitive difficulties but no history of head trauma, in elderly depressed patients, and in those with Alzheimer's disease.
While FDDNP can bind to both tau and amyloid in Alzheimer's patients, only a minority of CTE autopsies have identified amyloid plaques, suggesting that in these players, the high levels of binding signals are specific for tau.
"Using a tau marker for detection and tracking of neurodegenerative disease is critically important because severity of tau load, rather than amyloid burden, correlates with rates of neuronal loss," the researchers explained.
They noted that their findings should be interpreted with caution because of the limited number of players and the possibility that other factors such as genetics and overall cerebrovascular health might influence outcomes.
Small expressed hope that, if this diagnostic approach proves accurate in larger numbers, it may open the way to possible treatments.
"We know that inflammation is important both in Alzheimer's disease and traumatic brain injury, and in Alzheimer's we're testing anti-inflammatory and anti-tau treatments," he said.
"We also know that lifestyle choices and everyday health habits including diet, exercise, and stress management are important in protecting our brains," he added.