Semelhanças cognitivas inesperadas entre idosos e jovens: variabilidade e desempenho cognitivo

Abstract

Interindividual variability in cognitive performances has been investigated as they may provide important clues about the multivariate age-related cognitive decline. In the present work, we searched for cognitive variability, similarities, and differences between older and young people. For this, we used hierarchical cluster and canonical discriminant function analysis of cognitive scores using specific and sensitive tasks from the Cambridge Neuropsychology Test Automated Battery - CANTAB. Among 415 tested volunteers, three distinct cognitive groups were found, mainly based on working memory and episodic memory scores: group 1 (94% young adults) was composed almost exclusively of young adults, while groups 2 (82% older adults) and 3 (95% older adults) were composed predominantly of older adults. Although group 1was the youngest group with the highest level of education compared to the other groups, 18% of young people shared similar performances with older group 2 while 5% shared cognitive similarities with group 3. As compared to group 1, predominantly older groups 2 and 3 had equally lower scores in working memory, but as compared to group 3, group 2 showed greater performances in reaction time, sustained attention, and episodic memory. When the hierarchical cluster and discriminant function analyzes were limited to the same age group, we found 4 and 5 distinct clusters among young adults and older people respectively. Episodic memory, sustained attention, and reaction time most contributed to group formation in the older, while working memory and sustained attention contributed to cluster formation of young adults. Cognitive variability across subjects showed significant dispersion in rapid visual processing, spatial working memory, reaction time, and paired associated learning. The comparative analysis of these differences showed that they do not occur in the same direction and magnitude between individuals, cognitive domains, and tasks. We found that older adults with greater education and a more active lifestyle must have greater cognitive reserve and, therefore, deviated less from the reference group of young adults. Taken together, our data highlight the importance of studying variability as an instrument for the early detection of subtle cognitive declines and to interpret results that deviate from normality.