Stress hormones, sleep deprivation and cognition in older adults

Cognition can be deteriorated in older persons because of several potential mechanisms including the hormonal changes occurring with age. Stress events cause modification in hormonal balance with acute and chronic changes such as increase in cortisol and thyroid hormones, and simultaneous alterations in dehydroepiandrosterone sulphate, testosterone and insulin like growth factor-1 levels. The ability to cope with stress and regain previous healthy status, also called resiliency, is particularly impaired in older persons Thus, stressful conditions and hormonal dysregulation might concur to the onset of cognitive impairment in this population. In this review we address the relationship between stress hormones and cognitive function in older persons focusing on the role of one of the main stress factors, such as sleep deprivation (SD). We extracted and cross-checked data from 2000 to 2013 March and selected 112 full-text articles assessed for eligibility. In particular we considered 68 studies regarding the contribution of hormonal pathway to cognition in older adults, and 44 regarding hormones and SD both in rats and humans. We investigated how the activation of a stress-pattern response, like the one evoked from SD, can influence cognitive development and worsen cognitive status in the elderly. We will show the limited number of studies targeting the effects of SD and the consequent changes in stress hormones on cognitive function in this age group. We conclude that the current literature is not strong enough to give definitive answers on the role of stress hormonal pathway to the development of cognitive impairment in older individuals.