Obstructive Sleep Apnea (OSA)

Obstructive sleep apnea (OSA) is a primary sleep disorder caused by repeated partial or complete upper airway collapse despite an ongoing effort to breathe during sleep. It is estimated that 22 million Americans suffer from OSA, affecting 24% of men and 9% of women in the middle-aged population[1] and up to 62% of older adults aged 65 or over.[2] Epidemiological studies report that OSA patients are at a greater risk of having or developing depression[3-6] and cognitive impairment.[7] Individuals with major depressive disorder are five times likelihood to have OSA compared to the general population after controlling for obesity and HTN. Although the exact prevalence of cognitive impairment in patients with OSA is not known, a broad range of

OSA is an age-dependent disorder[11] due to increased upper airway collapsibility,[12] sleep fragmentation or arousals, and reduced N3 ( slow wave sleep) sleep that consolidates new memories.[13] Emergent evidence suggests that untreated OSA advances cognitive decline and increases the risk of developing cognitive impairment and dementia in the older adult population.[14-16] There is compelling data suggests: (1) adequate CPAP treatment potentially reverses impaired verbal memory in some patients;[17, 18] (2) long-term CPAP treatment significantly slows cognitive decline in patients with mild-to-moderate dementia comorbid with severe OSA compared to age-matched controls with no CPAP treatment;[19] and (3) better survival in elderly patients with OSA (aged 60+, n= 6,719) over the course of 10 years follow-up (hazard ratio= 0.62,

Thus, early detection and treatment of OSA has clinical and potential therapeutic application in elderly patients with cognitive impairment and /or depression comorbid with OSA. We reported the first epidemiological data showing that depression was associated with a 3-fold increased risk of converting to AD during follow-up over a 3-year period.[21] Postmodern longitudinal community and clinical studies support that depression is an independent risk factor for developing MCI and dementia[21-25] or an early manifestation of dementia.[26] However, we often do not know the etiology of many patients with depression and cognitive impairment. Some patients have incipient Alzheimer’s disease, some have cognitive impairment secondary to depression, and some have depression due to cerebral vascular disease initially described by the ‘Vascular Depression’ hypothesis.[27] Vascular depression is now recognized as a subtype of depression that is associated with C-SVD identified on MRI or DTI.[28-31] Since the changes in brain morphology relevant to depression and cognitive impairment have been observed in patients with moderate to severe OSA compared to healthy controls,[17, 18, 32-36] the biological links between OSA and vascular depression and OSA and cognitive impairment/dementia are