Olfactory Function and Associated Clinical Correlates in Former National Football League Players

Abstract

Professional American football players incur thousands of repetitive head impacts (RHIs) throughout their lifetime. The long-term consequences of RHI are not well characterized, but may include olfactory dysfunction. RHI has been associated with changes to brain regions involved in olfaction, and olfactory impairment is common after traumatic brain injury. Olfactory dysfunction is a frequent early sequelae of neurodegenerative diseases (e.g., Alzheimer's disease), and RHI is associated with the neurodegenerative disease, chronic traumatic encephalopathy (CTE). We examined olfaction, and its association with clinical measures, in former National Football League (NFL) players. Ninety-five former NFL players (ages 40-69) and 28 same-age controls completed a neuropsychological and neuropsychiatric evaluation as part of a National Institutes of Health-funded study. The Brief Smell Identification Test (B-SIT) assessed olfaction. Principal component analysis generated a four-factor structure of the clinical measures: behavioral/mood, psychomotor speed/executive function, and verbal and visual memory. Former NFL players had worse B-SIT scores relative to controls (p = 0.0096). A B-SIT cutoff of 11 had the greatest accuracy (c-statistic = 0.61) and specificity (79%) for discriminating former NFL players from controls. In the former NFL players, lower B-SIT scores correlated with greater behavioral/mood impairment (p = 0.0254) and worse psychomotor speed/executive functioning (p = 0.0464) after controlling for age and education. Former NFL players exhibited lower olfactory test scores relative to controls, and poorer olfactory test performance was associated with worse neuropsychological and neuropsychiatric functioning. Future work that uses more-comprehensive tests of olfaction and structural and functioning neuroimaging may improve understanding on the association between RHI and olfaction.

Utility of providing a concussion definition in the assessment of concussion history in former NFL players

“…Participants also completed standardized self-report and semi-structured interviews to assess behaviour and mood symptoms, including depression, suicidality, hopelessness, apathy, aggression, impulsivity, and hostility. A complete list of neuropsychological tests and measures of behaviour and mood have been reported elsewhere [32]. As described previously [32], Principal Component Analysis (PCA) generated four factors from the neuropsychological and behaviour/mood measures and included: Behavioural/mood, Psychomotor Speed/Executive Function, Verbal Memory, and Visual Memory.…”

“…A complete list of neuropsychological tests and measures of behaviour and mood have been reported elsewhere [32]. As described previously [32], Principal Component Analysis (PCA) generated four factors from the neuropsychological and behaviour/mood measures and included: Behavioural/mood, Psychomotor Speed/Executive Function, Verbal Memory, and Visual Memory. PCA was performed to minimize the number of analyses and reduce type I error risk.…”

History of Sport-Related Concussion and Long-Term Clinical Cognitive Health Outcomes in Retired Athletes: A Systematic Review

“…Six studies 15,32,35,46,52,55 used subjective (self-reported) cognitive tests alone. The re-* References 14,19,21,23,24,27,28,30,34,36,37,39,41,43,44,47,[49][50][51]55. †References 16,18,20,25,35,40,42,45,46,48,52 (Figure 3). Memory was the most commonly studied cognitive health outcome (n ¼ 31, 67%), followed by attention (n ¼ 17, 37%) and global cognitive ability (n ¼ 16, 35%).…”

“…Tests of attention were administered in 17 (37%) of 46 investigations. † † In 3 studies, 23,28,31 investi- Table 2). The authors of 14 (45%) studies § § reported normal functioning on memory tests.…”

“…16,34,37,54,56 Six (55%) studies 13,16,28,31,37,56 demonstrated decreased executive function in retired athletes, whereas the remaining 5 (45%) studies did not. 23,34,41,44,54 Three studies 16,37,56 showed decreased performance on the Wisconsin Card Sorting Test in retired athletes compared with control participants. Wright et al 28 found that retired NFL players displayed deficits in executive ability compared with normative data (Heaton system: 37.5%; Wechsler system: 20.0%).…”