Do cognitive reserve, current cognitive functioning, depression and age affect the subjective cognitive decline in Polish adults?

Introduction
Subjective cognitive decline (SCD) may reflect cognitive deficits or be associated with depression. Cognitive reserve (CR), understood as rich and varied experiences and knowledge gained during life, may promote the cognitive condition in the late years of life, protect against depression and reduce the SCD. The results of previous studies are not uniform. The aims of the research were to determine whether and how the level of CR, depression intensity, age and level of cognitive functions predict the risk of a higher sense of cognitive difficulties in adults, whether the analyzed compounds will manifest themselves in relation to different types of complaints and will characterize different groups of adults.

Material and methods
The research included two independent groups (N1 = 130, N2 = 90) of adult Poles. To assess cognitive functions, the M^oCA test was used, to assess the intensity of depression, BDI II was used, and to assess the intensity of sense of cognitive difficulties, DEX-S, MFS, SCL and MMQ were used. The CR indicator was the sum of points obtained in the questionnaire regarding activity in various spheres of life, level of education and professional activity.

Results
Higher severity of depression increased the risk of SCD, while better cognitive performance reduced this risk. Cognitive reserve and age were not predictors of higher SCD.

Conclusions
There are various mechanisms of SCD: associated with a higher level of depressive mood and/or related to cognitive deficits. The role of depressive mood in SCD is more important in younger adults, while with age the role of actual cognitive performance in formulating SCD increases.