Identification des facteurs de risque de développer une démence de type Alzheimer à la suite d’un traumatisme craniocérébral et caractérisation des profils neuropsychologiques

There are many causes of cognitive decline in older adults. The most prevalent is Alzheimer’s disease (AD). Another common cause of cognitive decline in older adults is traumatic brain injury (TBI). Advanced age and cognitive decline in the elderly are also risk factors for falls. Thus, among some elderly individuals, AD and TBI may be comorbid conditions. It seems that TBI increases the risk of AD, but this link is still poorly understood in the literature. Despite the increase prevalence of TBI and AD in recent years, very few studies agree on the effect of TBI on the risk of developing AD and the associated risk factors. Also, few studies have looked at the neuropsychological profiles associated with those two neurological conditions in order to aid in differential diagnosis. This thesis aims to identify the characteristics linked to TBI which are associated with the risk of developing Alzheimer's type dementia, to characterize the neuropsychological profile of elderly TBI patients, AD patients and healthy individuals, as well as to identify the factors influencing the cognitive functions.  The thesis includes one systematic review and one empirical study. The first investigates if certain traumatic brain injury (TBI)-related variables can predict the risk of developing post-TBI Alzheimer’s disease (AD) in adults. A total of 18 studies were included in the review. Specific TBI-related variables, such as TBI severity, loss of consciousness (LOC) and post-traumatic amnesia (PTA) were documented as possible predictors of AD. Failure to establish such a link may be related to methodological differences within and across studies.   The aim of the second article was to assess the differences in neuropsychological profiles of older adults with mild traumatic brain injuries (mTBI) and with Alzheimer’s disease (AD). The sample included older adults with mTBI (n = 24), older adults with AD (n = 29), and healthy older adults (n = 24). A battery of cognitive tests and standardized questionnaires were administered to all participants in a standardized fashion during a neuropsychological evaluation. Demographic and injury factors were examined as potential predictors of cognitive outcomes. Results revealed group differences across all cognitive functions. Also, the number of years of education and the number of days since the accident were associated with some cognitive functions for the TBI group. However, no variable was associated with cognitive functioning in the AD group.  Although this thesis does not clearly identify the factors related to TBI that would increase the risk of developing AD, it demonstrates that a TBI in old age can impair cognitive functioning. The neuropsychological profiles of elderly patients with mTBI differ significantly from that of AD patients and normal aging. This thesis also highlights that the recovery time as well as the level of education seem to be protective factors following mTBI for some cognitive functions. These results are of great importance considering that the population of seniors will increase considerably over the next decades and will lead clinicians to have to take a position on the diagnosis and the future of patients.

Keyphrases: Alzheimer, Traumatic brain injury, Alzheimer's disease, Dementia, Cognitive decline, Cognitive functioning, Neuropsychology, Outcome, Older people, Elderly