[Obstructive sleep apnea and cognitive impairment in the elderly]

Obstructive Sleep Apnea Syndrome (OSAS) is characterized by repeated episodes of upper airway obstruction during sleep that result in intermittent hypoxemia and arousal. The prevalence of OSAS increases with aging, occurring in up to 25% of older adults and up to 48% in patients with Alzheimer's disease. OSAS causes hypoxia, fragmented sleep, daytime sleepiness, cognitive dysfunction, functional decline, and brain damage resulting from reduced cerebral blood flow, ischemic brain lesions, microvascular reactivity, white matter lesions, and grey matter loss. OSAS is considered as an independent risk factor for hypertension, stroke and mortality. The treatment of choice for OSAS is continuous positive airway pressure (CPAP). OSAS-related cognitive dysfunction has been shown in a variety of domains including attention, executive functioning, motor efficiency, working memory, and long-term episodic memory. Proposed mechanisms include hypoxemia, sleep fragmentation and inflammatory process, but it remains unclear which mechanisms underlie the relationship between OSAS and disturbances in the different cognitive domains. Recent studies suggest that OSAS may exacerbate cognitive functioning in dementia and that CPAP therapy can be applied to these patients and improve cognitive functioning.