Good Sleep for Brain Health by M. Chris Wolf

One possible (but as yet unexplored) explanation for the sleep disruptions and memory deficits experienced by these patients is that the periods of sub- and- supra-physiological cortisol concentrations they experience may have a specific negative impact on processes of sleep-dependent memory consolidation. Patients with AD report and experience both poor-quality sleep and cognitive difficulties ( 3– 8). However, replacement medication does not restore the natural circadian rhythm of cortisol and, despite adherence, patients experience sub/supra physiological cortisol concentrations, particularly during the night. Patients with Addison’s disease (AD) require lifelong glucocorticoid replacement therapy. Of particular interest here is that cortisol appears to play a particularly important role in mediating the sleep-memory relationship, especially because of its function in maintaining the integrity of sleep architecture ( 1, 2). Available neuroscience literature provides some of the sought-after answers, suggesting that healthy, uninterrupted sleep is vital to ensuring that, for instance, consolidation of memory traces acquired during waking hours occurs smoothly and efficiently. Nonetheless, questions about the functions of sleep (e.g., whether it is necessary for more than simple physical and mental restoration) remained unanswered until relatively recently.

Sleep is a critical biological process, an inevitable and essential aspect of normal human physiology. This review summarizes the literature on sleep and cognition in AD, and the role that cortisol concentrations play in the relationship between the two.

Given the literature linking sleep disruption and cognitive impairment in AD, future initiatives should aim to improve patients’ cognitive performance (and, indeed, their overall quality of life) by prioritizing and optimizing sleep. Available data provides support for existing theoretical frameworks which postulate that in AD and other neuroendocrine, neurological, or psychiatric disorders, disrupted sleep is an important biological mechanism that underlies, at least partially, the memory impairments that patients frequently report experiencing. These disruptions and impairments may be related to the failure of replacement regimens to restore a normal circadian rhythm of cortisol secretion. Patients with Addison’s disease (AD) experience consistent and predictable periods of sub- and supra-physiological cortisol concentrations due to lifelong glucocorticoid replacement therapy, and they frequently report disrupted sleep and impaired memory. Neuroscientific literature suggests there are mechanistic relations between sleep disruption and memory deficits, and that varying concentrations of cortisol may play an important role in mediating those relations. Sleep is a critical biological process, essential for cognitive well-being.

Good Sleep for Brain Health by M. Chris Wolf