Associations of Traumatic Brain Injury and Mild Behavioral Impairment With Cognitive Function and Dementia.

Objective: Traumatic Brain Injury (TBI) may contribute additional complexity to the clinical picture of mild behavioral impairment (MBI). MBI, a behavioral analog to mild cognitive impairment (MCI), is comprised of five neuropsychiatric domains: decreased motivation, affective dysregulation, impulse dyscontrol, social inappropriateness, and abnormal perception/thought content. We investigated (1) if cross-sectional associations of cognitive status with MBI symptoms differ by TBI status and (2) if prospective associations of MBI domain positivity with incident dementia risk differ by TBI status.

Methods: 2246 participants without dementia from the Atherosclerosis Risk in Communities Study were included (mean age = 75.6 years, 59.0% female). TBI was defined by self-report/ICD-9/10 codes, MBI via an established algorithm based on the Neuropsychiatric Inventory Questionnaire, and baseline cognitive status/incident dementia using neuropsychological tests, informant interviews, and hospital/death certificate codes.

Results: Cross-sectionally, although MCI status was associated with greater odds of MBI, this did not differ based on TBI status (MCI with TBI: OR = 2.04, 95% CI = 1.44-2.88, MCI without TBI: OR = 1.60, 95% CI = 1.20-2.14). Individuals with MCI (with or without TBI) were more likely to have decreased motivation, affective dysregulation, and impulse dyscontrol. Prospectively, positivity in 1+ MBI domains was associated with increased risk of incident dementia, not differing by TBI status (no TBI and MBI: HR = 2.15, 95% CI = 1.55-2.99, TBI and MBI: HR = 2.62, 95% CI = 1.81-3.80).

Conclusions: Neither cross-sectional associations between cognitive status and MBI domain positivity nor prospective associations of MBI domain positivity with incident dementia risk differed by TBI status. How TBI may relate to neuropsychiatric symptomatology in the context of neurodegenerative processes requires further clarification.