Importance of psychological factors on the adrenocortical functioning and subjective memory complaints

Abstract

Stress has been considered one of the main problems in today’s society, given that it has been related to several mental and physical health conditions, as well as age-related diseases and memory problems. However, there are individual differences in the way people face stressful situations. In this sense, some people, despite being exposed to the same levels of stress, do not develop pathologies, suggesting that certain psychological factors could act as protectors from the effects of stress. Resilience, which encompasses positive and optimistic thoughts, has been understood as the ability to face adversity and recover from stressful situations. More importantly, it has been proposed as an important factor associated with better health and successful aging. Among the age-related disorders, greater attention has been paid to cognitive decline and early dementia detection. The current priority is to study which factors could prevent or delay cognitive impairment. In this regard, Subjective Memory Complaints (SMCs) over time, or Subjective Cognitive Decline (SCD), have been indistinctly suggested as a proxy for early dementia detection in older people. However, these SMCs also appear in young individuals, increasing the need to determine which factors could be associated with this phenomenon at different ages. All of this highlights the importance of studying how certain psychological factors, especially protective factors, could be related to stress and SMCs across the lifespan, but especially in older people because it is a stage of greater vulnerability to both stress and memory decline. In this doctoral thesis, the two main issues of concern in today's societies are addressed, that is, stress and early detection of dementia and how different psychological factors can affect them. For this purpose, psychological factors of resilience (positivity, optimism) and vulnerability (pessimism) have been related to different stress biomarkers (saliva and hair) and contexts (response to a stressor and chronic stress) in healthy older people. Secondly, the relationship between SMCs and different vulnerability factors (anxiety and depression), protective factors (resilience and positivism), stress (basal functioning of the Hypothalamic Pituitary Adrenal axis [HPA axis]), and neurodegenerative biomarkers of Alzheimer’s disease (AD) and Cerebrovascular Disease (CVD) have been addressed. This second general objective has also been addressed in different age groups (i.e., healthy young, middle-aged, and older people). In sum, this doctoral thesis helps to clarify the role of some psychological and stress indicators, in order to enhance and encourage future research and interventions focused on improving health and healthy aging.