Modelos de associação entre depressão e funções cognitivas: uma via bidirecional

Abstract

This study aimed to present, under different perspectives, models of association between depression and cognitive functions. For this, two studies were developed: the first aimed to determine the level of association between depressive symptoms and the cognitive abilities of institutionalized older persons, and the second approaches a neurobiological hypothesis that the interaction between depression and cognitive decline is mediated by corticosteroids, generating a downregulation in the BDNF. Regarding the method, the first study is cross- sectional and involved 69 older adults living in Long-Term Care Facilities for the older persons (LTCFs), with tracking of their depressive symptoms and their physical and cognitive performance, investigated through tests and specific scales. Thus, the Geriatric Depression Scale (GDS) of 30 items was used to categorize the groups between those with depressive symptoms (score of 10 or more) and asymptomatic ones. About cognitive tests: The Mini Mental State Examination (MMSE) was used to quantify global cognition, containing 11 items that access cognitive domains such as: orientation, memory, calculation, language and praxis. The Verbal Fluency (VF) test was used to access semantic fluency and executive function through the maximum number of animal name recalls in 60 seconds. Digit Span Forward (DSF) and Digit Span Backward (DSB) were used to access short-term and working memory respectively. DSF is a repetition of a numerical sequence in the same order and DSB in reverse order. On the physical evaluations, the 2-minute Stationary Walking Test (2MST) and the Sit-to-Stand Test were used. The first one evaluates the subject's aerobic resistance by means of the maximum number of steps completed in two minutes. In the second test, the subject must sit and stand continuously for 30 seconds to estimate the functional capacity of the lower limbs. The second study uses in silico analysis as a method of inserting genes into the GeneCards database to explore the genes encoding proteins associated with depression and cognitive decline, in which these genes were inserted into the String bioinformatics database. for viewing network interaction. Among the results, in the first study, it was evidenced that the older adults with worse physical and cognitive performance exhibited the presence of depressive symptoms, and those with a greater deficit in short-term memory were 5 times more likely to have depressive symptoms (OR = 4.86; CI = 1.09; 21.69). In the silico analysis, the network of interactions between the genes suggested the association between depression and cognitive decline mediated by inflammatory factor (TNF-α) associated with precursors of glucocorticoid hormones (POMC and CRH).In this way, the importance of better understanding how the association between depression and cognitive decline occurs, since these mechanisms feedback each other and can be better explained by an integral model that contemplates the biological and psychological dimensions, in order to provide more efficient interventions that address the problem holistically.