Impact of Mild Head Injury on Neuropsychological Performance in Healthy Older Adults: Longitudinal Assessment in the AIBL Cohort

Abstract

Traumatic brain injury (TBI) is suggested to be a significant risk factor for dementia. However, little research has been conducted into long-term neuropsychological outcomes after head trauma. Participants from the Australian Imaging, Biomarkers and Lifestyle Study of Ageing (AIBL) who had recovered after sustaining a mild TBI involving loss of consciousness more than 5 years previously were compared with matched controls across a 3-year period. Bayesian nested-domain modeling was used to estimate the effect of TBI on neuropsychological performance. There was no evidence for a chronic effect of mild TBI on any neuropsychological domain compared to controls. Within the TBI group, there was some evidence suggesting that the age that the head trauma occurred and the duration of unconsciousness were modulators of episodic memory. However, these findings were not robust. Taken together, these findings indicate that adults who have sustained a TBI resulting in loss of consciousness, but who recover to a healthy level of cognitive functioning, do not experience frank deficits in cognitive ability.

Keywords: Bayesian; ageing; cognition; episodic memory; longitudinal; mild traumatic brain injury.

Figure 1

Effect of Traumatic brain injury (TBI) on cognitive performance. The influence of TBI on neuropsychological performance across outcomes and domains comparing Head Injury absent participants (TBI⁻, blue circles and lines) with Head Injury present participants (TBI⁺, red circles and lines). Displayed are the mean (±80, 95% highest density intervals (HDIs)) parameter estimates from the nested domain model; these are equivalent to partial correlation coefficients. Individual parameter estimates are shrunk towards each other within domains, and domains are shrunk towards a common estimate. Positive indicates better performance (Intercept) or improvement in performance over time (Longitudinal slope). Overall, there was little difference in cognitive performance (left) or decline (right) between TBI⁺ or TBI⁻ participants. N = 102 TBI⁻ and 52 TBI⁺ participants. Domains: D1—Primary Memory, D2—Perceptual Speed, D3—Verbal Memory, D4—Visuospatial Function, D5—Visual Memory, D6—Verbal Ability, D7—Interference.

Figure 2

Effect of the age of TBI and duration of unconsciousness on cognitive performance. The influence of the age at first TBI and the duration of loss of consciousness on neuropsychological performance across outcomes and domains among individuals who had previously experienced a TBI. Presented are the mean (±80, 95% HDI) parameter estimates for the nested domain model that included age at first TBI, duration of loss of consciousness, time since entry into the study along with the covariates age, sex, and wechsler test of adult reading (WTAR). Parameter estimates are equivalent to partial correlation coefficients. N = 52. Domains: D1—Primary Memory, D2—Perceptual Speed, D3—Verbal Memory, D4—Visuospatial Function, D5—Visual Memory, D6—Verbal Ability, D7—Interference.