Prevalence of low scores in the Uniform Data Set version 3.0: Comparison of older adults with and without a self-reported history of traumatic brain injury.

Objective: To assess for differences in low score frequency on cognitive testing amongst older adults with and without a self-reported history of traumatic brain injury (TBI) in the National Alzheimer's Coordinating Center (NACC) dataset.

Method: The sample included adults aged 65 or older who completed the Uniform Data Set 3.0 neuropsychological test battery (N = 7,363) and was divided by individuals with and without a history of TBI, as well as cognitive status as measured by the CDR. We compared TBI- and TBI + groups by the prevalence of low scores obtained across testing. Three scores falling at or below the 2^nd percentile or four scores at or below the 5^th percentile were criteria for an atypical number of low scores. Nonparametric tests assessed associations among low score prevalence and demographics, symptoms of depression, and TBI history.

Results: Among cognitively normal participants (CDR = 0), older age, male sex and greater levels of depression were associated with low score frequency; among participants with mild cognitive impairment (CDR = 0.5-1), greater levels of depression, shorter duration of time since most recent TBI, and no prior history of TBI were associated with low score frequency.

Conclusions: Participants with and without a history of TBI largely produced low scores on cognitive testing at similar frequencies. Cognitive status, sex, education, depression, and TBI recency showed variable associations with the number of low scores within subsamples. Future research that includes more comprehensive TBI history is indicated to characterize factors that may modify the association between low scores and TBI history.