Mild cognitive impairment : improved identification and a novel cognitive intervention.
Degree GrantorUniversity of Canterbury
Degree NameDoctor of Philosophy
The prevention and treatment of cognitive impairment in the elderly has assumed increasing importance given the ageing population. Mild Cognitive Impairment (MCI) is considered as a transitional state between healthy ageing and dementia. The primary aim of the current study was to develop a cognitive intervention for MCI that encourages participation in a variety of complex and novel cognitive activities, and to examine its efficacy. Furthermore, these cognitive activities were developed to influence multiple brain networks, particularly the default mode network (DMN). A secondary aim was to assess the diagnostic utility of a number of screening measures in discriminating MCI. In the Cognitive Screening Study, 609 individuals (age range 65-97 years old) were evaluated using brief cognitive tests, including the Montreal Cognitive Assessment (MoCA), Rey Complex Figure Test (RCFT; copy and 3-min recall), and Trail Making Test-Part A (TMT-A). After the initial evaluation, 222 were excluded, the remaining were classified as Probable MCI (n = 75), Possible MCI (n = 72) and Probable Healthy Control (HC; n = 240). A portion of these individuals were followed-up with detailed cognitive assessment, and their performance on the detailed assessment determined which cognitive group they were assigned to. As a result, 17 individuals were classified as Confirmed MCI, 91 as Possible MCI, and 226 as Probable HC. The diagnostic utility of each individual screening measure was examined using the standard receiver operating characteristic curve (ROC). Multivariate logistic regression analysis was conducted to investigate whether combinations of the screening instruments improved the detection of MCI. Simultaneous discriminations among the three cognitive classes were examined using three-dimensional ROC. The results revealed that both MoCA and RCFT (copy and 3-min recall) demonstrated good discrimination of MCI, however, the combination of the two tests showed even better discriminatory power. Thirteen MCI participants were included in the Cognitive Enrichment Study, these individuals were randomly allocated to either the intervention (n = 6) or waitlist group (n = 7). Those in the intervention group received the 4-month-long Cognitive Enrichment Programme. Although the neuropsychological results were generally non-significant, we found a significant pre-post-effect on a measure of long-term memory retrieval. Furthermore, this study also used functional magnetic resonance imaging (fMRI) to examine the effect of enrichment on the DMN in MCI. DMN activity and connectivity were recorded pre- and post-enrichment. An increase in resting-state DMN connectivity was found in intervention participants, while the waitlist group showed a reduced connectivity. The changes in DMN connectivity were associated with an improvement on tests of executive function. However, there were no enrichment-related changes in DMN activation and deactivation. In conclusion, these results suggest some beneficial effects of cognitive enrichment on cognitive abilities, as well as DMN connectivity. Results from the current study, however, should be interpreted with caution because of the small sample size. Further larger trials are needed to confirm the preliminary findings of this study.