Exercise, the diurnal cycle of cortisol and cognitive impairment in older adults

Abstract

Exercise has been shown to reduce the risk of developing Mild Cognitive Impairment and Alzheimer's disease as well as to improve cognition in healthy and cognitively impaired individuals. However, the mechanisms of these benefits are not well understood. The stress hypothesis suggests that the cognitive benefits attributed to exercise may partially be mediated by changes in the cortisol secretion pattern. Chronic stress may increase the risk of AD and exacerbate the cognitive deficits and brain pathology characteristic of the condition while physical activity has been shown to attenuate most of stress consequences and risk factors for AD. Initially, research on the effects of cortisol on cognition and physical activity focused on cortisol levels at one time point but the circadian pattern of cortisol secretion is complex and it is still unclear which aspects are most closely associated with cognitive function. Thus, the aim of this review was to analyze the exercise/stress/cognition hypothesis focusing on the effects of the diurnal cycle of cortisol on cognitive function and physical activity in older adults with and without cognitive impairment.

Effects of Exercise on Cognitive Performance in Older Adults: A Narrative Review of the Evidence, Possible Biological Mechanisms, and Recommendations for Exercise Prescription

“…In contrast, a longitudinal study of 52 older adults found that higher cortisol levels were associated with slower cognitive decline in those with MCI but not in those with normal cognition [99]. Cortisol is known to be susceptible to considerable fluctuations throughout the day [100], whereby cortisol levels increase upon waking, then steadily decline throughout the day [101]. is difficulty in measuring cortisol levels may explain some of the discrepancies in the aforementioned studies.…”

Therapeutic implications of hypothalamic-pituitaryadrenal-axis modulation in Alzheimer’s disease: A narrative review of pharmacological and lifestyle interventions

“…Despite an abundance of studies investigating the role of PA and physical performance on cortisol levels (see also Tortosa-Martinez et al, 2018), very few experimental studies have investigated how these observations play out as a function of cognitive health, and none, to our knowledge, have investigated associations with reduced dementia and/or AD risk among older adults. One study of cognitively healthy sedentary older adults (n=27) explored the role of an aerobic exercise intervention on cognitive health and cortisol levels across a 6-month period (Drogos et al, 2019).…”

Hair Cortisol Concentration as a Biomarker of Sleep Quality and Related Disorders

“…In fact, altered cortisol concentrations have been reported in a number of diseases of the central nervous system, such as psychiatric disorders, e.g., posttraumatic stress disorder [ 12 , 13 , 14 ], schizophrenia [ 15 ], depression [ 16 , 17 , 18 , 19 ], anxiety [ 20 , 21 , 22 ], and cognitive impairment [ 23 , 24 , 25 ]. Changes in the peripheral levels of cortisol have also been reported in certain neurodegenerative conditions, such as Huntington’s disease [ 26 ] or Alzheimer’s disease [ 27 ].…”

“…There is a high correlation between salivary cortisol levels and unbound cortisol in plasma and serum, which remains high during the circadian cycle and under different dynamic tests, such as adrenocorticotropic hormone (ACTH) stimulation [ 39 , 40 ]. Since free cortisol represents the biologically active hormone fraction, salivary cortisol measures have early been considered as a better method than serum cortisol for the evaluation of adrenocortical function; however, cortisol measurement in blood and saliva samples should be performed at different timepoints within the same day because of cortisol circadian rhythm, and it is recommended to repeat cortisol measurements in blood and saliva samples in different days since many factors can acutely influence cortisol secretion [ 23 , 24 , 25 , 39 , 40 ]. The role of hypercortisolemia in the pathophysiology of sleep disorders and neuro-psychiatric disorders accompanied by sleep alterations can only be demonstrated through measures that reflect prolonged exposure to cortisol, since such disorders are typically chronic conditions.…”