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Sleep disturbances, sleep-disordered breathing, and cognitive impairment in older adults: perioperative implications

The mechanisms behind sleep have been studied in the last few decades, illustrating a complex process of sleep-wake cycles regulated by interactions and connections between various regions andnuclei in the brain. Many of these regions are involved in memory and cognitive function. Sleep also changes with increasing age, with observed changes in individuals over 60 years including decreased total sleep duration, decreased slow-wave sleep and rapid eyemovement (REM), increased time awake after sleep onset (WASO), and decreased sleep efficiency. While some of these changes may be physiological, others may be due to neurocognitive or neurodegenerative processes. The impact of sleep disturbances is multifaceted. Poor sleep is associated with reduced cognitive, affective, and physiological responses to stressors, physical diseases across all organ systems, and mood disorders. Mounting evidence also supports a link between sleep disturbances, including poor sleep quality, excessive daytime sleepiness, andboth short (typically<6 hof sleep a night) and long (typically >9 h of sleep a night) sleep duration with cognitive impairment. Furthermore, sleep disturbances, sleep-disordered breathing (SDB), or abnormal respiratory patterns occurring during sleep also increase the risk of cognitive decline in older adults (age over 60 y), and may also increase the risk of various postoperative complications including postoperative delirium (POD). The objective of this review is to examine the current evidence regarding the effect of and proposed mechanisms behind sleep disturbances and SDB [with a focus on obstructive sleep apnea (OSA)], with cognitive decline and impairment. The possible association of sleep disturbances and SDB with postoperative complications will be discussed, along with the potential utility of continuous positive airway pressure (CPAP) therapy and sleep hygiene in preventing these complications.