Caractérisation de la plainte cognitive dans le vieillissement normal et le trouble cognitif léger

Faced with the serious demographic challenge of an aging population, it is increasingly important to better understand the changes that occur with advancing age. It is known that aging is associated with many cognitive modifications. Indeed, approximately 25 to 50% of elderly individuals aged 65 and over report cognitive and memory declines. The work presented in this thesis focuses on the characterization of the cognitive complaint in healthy older adults and in individuals with mild cognitive impairment (MCI) and the changes in the complaint as they progress into the Alzheimer’s disease continuum. The first study (Chapter II) aimed to identify main domains of memory complaint in middle-aged and older adults. It also sought to determine whether the domains of complaint were related to cognitive performance on neuropsychological tests. The impact of personal characteristics (age, gender, education and level of depression) on complaint was also assessed. A total of 115 healthy adults between the ages of 45 and 87 completed the Self-Evaluation Questionnaire (QAM; Van der Linden, Wijns, Von Frenkell, Coyette, & Seron, 1989) and were tested with a comprehensive neuropsychological battery. A principal component analysis performed on the items of the QAM identified seven dimensions of complaint. Difficulty inhibiting internal and external sources of interference when learning or remembering something was the main area of complaint. Other analyses revealed that complaints related to a set of memory failures that appear to be more detrimental to autonomy and safety indicated more severe cognitive and functional difficulties. The results also indicated that the main domains of complaint generally reflected objective cognitive problems. There was no association between cognitive complaint and almost all demographic characteristics. The second study (Chapter III) aimed to characterizing the cognitive complaint in MCI and its changes as individuals progress into the Alzheimer’s disease continuum. Another goal of this study was to verify whether changes in domains of cognitive complaint were associated with the increasing cognitive deficits experienced by those with progressive MCI. Individuals with MCI and healthy older adults were tested yearly over a three-year period. Complaint was measured using the QAM and the Multifactorial Memory Questionnaire (MMQ; Fort, Holl, iv Kaddour, & Gana, 2004). Our findings revealed that individuals with progressive MCI reported more cognitive complaints in relation to memory for complex information (e.g., text or conversation), for events from the recent past and for information about familiar people than healthy older adults, and this was found up to three years prior to the dementia diagnosis. When examining group effects, there were no changes in the level of complaint over time. Awareness of difficulties may become compromised in a proportion of individuals with progressive MCI. However, correlational analyses indicated that an increase in three domains of complaints was associated with the increasing cognitive deficits over the 3-year period. Thus, complaint in MCI may help to better understand the cognitive difficulties the individual person with MCI is experiencing. The theoretical and clinical implications of these findings are discussed in Chapter IV.

Keyphrases: Subjective cognitive complaint, Mild cognitive impairment, Alzheimer’s disease, Normal aging, Memory, Neuropsychology