Análise dos efeitos do estresse crônico e do envelhecimento sobre a cognição de cuidadores familiares de pacientes com doença de Alzheimer e sua relação com os níveis de cortisol, DHEA e BDNF

Abstract

The growth of elder population is a global occurrence and is followed by an increased prevalence and incidence of dementia, especially Alzheimer disease (AD). As the disease progresses, there is a larger demand for special care, task mainly performed by their family, who mostly are also elderly spouses of the patients. These caregivers are being constantly afflicted by chronic stress, which in turn can become harmful to their health in a number of disorders, such as cognitive impairment. Current literature highlights: (I) Relation between chronic stress, aging and cognitive impairment; (II) Relation between chronic stress and changes on hormone levels, such as cortisol and dehydroepiandrosterone (DHEA), and neurotrophic factors, i.e. Brain-Derived Neurotrophic Factor (BDNF); (III) BDNF, DHEA and cortisol potentially modulate cognitive-related mechanisms. In the present study, the evidences were assessed conjointly to better characterize physiological and pathological mechanisms involved in the association between chronic stress, aging and cognitive deficits. Chronic stress effects on frontal and temporal lobes-dependent cognitive functions were investigated in familial caregivers of AD patients (n=17; 32 to 84 years old). The impact of chronic stress on cortisol, DHEA and BDNF levels was also assessed, and the relation of these physiological features on cognitive performance. Initial findings point that chronic stress is capable of impairing attention, executive functions and declarative memory, also increasing cortisol/DHEA ratio and reducing serum BDNF levels. Then, we assessed age effects on the relation of chronic stress, cognition; cortisol, DHEA, and BDNF, as older caregivers are, theoretically, more prone to chronic stress effects than its younger counterparts are. Our results supports this hypothesis, indicating that hormone and cognitive changes are of greater importance on older caregivers when compared with young caregivers. However, middle-aged caregivers also presented a significant cognitive impairment and more suceptibility to chronic stress effects on BDNF levels than older caregivers. The results presented in this thesis highlights that chronic stress-related cognitive alterations are resulting from, at least partly, cortisol, DHEA and BDNF level changes. However, the rate in which these cognitive features are affected, and its relation with the assessed hormones and neurotrophin are dependent on the caregivers’ age.