Mediatory effect of depression in the relations between cognitive reserve and cognitive abilities. Does a CR index matter?

Abstract

Background Cognitive reserve (CR) explains the level of cognitive functioning in healthy aging individuals or those with brain dysfunctions. Various CR indexes include objective (e.g. education level), subjective (e.g. self-report methods of life activity), and their combinations. Data showing the impact of CR on cognitive performance are unclear due to the relationship between CR and depressive mood as well as due to the impact of depressed mood on cognitive functions. The current study was designed to determine the link between three different CR indicators and cognitive abilities of adult Poles. The analyses took into account intensity of depression, as a mediator for these links. Additionally, the study was designed to assess whether or not the contents of the self-reported part of the CR index were of significance for the relations. participants and procedure The study was carried out in two unrelated groups of adult Poles (Group I, n = 130; Group II, n = 90). Assessment of CR took into account three indexes (CR based on self-reported activity in life, CR additionally containing information on formal education, and CR supplemented with information related to occupational activity). Cognitive capacity was assessed using the Montreal Cognitive Assessment Scale (MoCA), Vocabulary, as well as Digit Span Forward and Backwards. Intensity of depression was measured using Beck Depression Inventory (BDI) II. The self-report part of the questionnaire used to measure CR in Group I contained items mainly about past life and in Group II consisted of more items about both past life and current activity. results The greater CR corresponds to higher scores in cognitive tasks and lower intensity of depressive mood. This is in line with previous research reporting that a higher level of the reserve may protect against mood disorders. Depression mediates the links between CR and the cognitive functions, reducing the positive impact of CR. These relations were visible in Group I, where CR based on self-reported activity in life comprised items about (mainly) past life. conclusions Self-report techniques used in CR assessment may be inadequate as a tool for describing the reserve, due to the link between self-report and emotional state. However, a more detailed self-report component of the CR indicator about both past and current life may correspond to a weaker or insignificant relation between CR and depressive mood as well as between depression and cognitive capacities. Varied approaches to operationalisation of CR result in discrepancies regarding the role of resources in the stabilisation and dynamics of cognitive status in ageing people and in clinical groups.