Role of Obstructive Sleep Apnea in Cognitive Impairment.

Obstructive sleep apnea (OSA) is a prevalent sleep related breathing disorder characterized by repetitive collapse of the upper airways leading to intermittent hypoxia and sleep disruption. Clinically relevant neurocognitive, metabolic and cardiovascular disease often occurs in OSA. Systemic hypertension, coronary artery disease, type 2 diabetes mellitus, cerebral vascular infarctions and atrial fibrillation are among the most often cited conditions with causal connections to OSA. Emerging science suggest that untreated and undertreated OSA increases the risk of developing cognitive impairment, including vascular dementia and neurodegenerative disorders, like Alzheimer's disease. As with OSA, cardiovascular disease and type 2 diabetes mellitus, the incidence of dementia increases with age. Given our rapidly aging population, dementia prevalence will significantly increase. The aim of this treatise is to review current literature linking OSA to dementia and explore putative mechanisms by which OSA might facilitate the development and progression of dementia.

Obstructive Sleep Apnea Phenotypes and Markers of Vascular Disease: A Review.

Obstructive sleep apnea (OSA) is a chronic and heterogeneous disorder that leads to early mortality, stroke, and cardiovascular disease (CVD). OSA is defined by the apnea-hypopnea index, which is an index of OSA severity that combines apneas (pauses in breathing) and hypopneas (partial obstructions in breathing) associated with hypoxemia. Yet, other sleep metrics (i.e., oxygen nadir, arousal frequency), along with clinical symptoms and molecular markers could be better predictors of stroke and CVD outcomes in OSA. The recent focus on personalized medical care introduces the possibility of a unique approach to the treatment of OSA based on its phenotypes, defined by pathophysiological mechanisms and/or clinical presentation. We summarized what is known about OSA and its phenotypes, and review the literature on factors or intermediate markers that could increase stroke risk and CVD in patients with OSA. The OSA phenotypes where divided across three different domains (1) clinical symptoms (i.e., daytime sleepiness), (2) genetic/molecular markers, and (3) experimental data-driven approach (e.g., cluster analysis). Finally, we further highlight gaps in the literature framing a research agenda.

Obstructive sleep apnea and stroke: links to health disparities.

Obstructive sleep apnea (OSA) is a novel cardiovascular and cerebrovascular risk factor that presents unique opportunities to understand and reduce seemingly intractable stroke disparity among non-Hispanic blacks and Hispanic/Latinos. Individuals from these 2 groups have up to a 2-fold risk of stroke and greater burden of OSA. Obstructive sleep apnea directly and indirectly increases risk of stroke through a variety of autonomic, chemical, and inflammatory mechanisms and vascular risk factors such as hypertension, obesity, and diabetes mellitus. Untreated OSA exacerbates poststroke prognosis, as it may also influence rehabilitation efforts and functional outcomes such as cognitive function after a stroke. Conversely, treatment of OSA may reduce the risk of stroke and may yield better poststroke prognosis. Unfortunately, in racial/ethnic minority groups, there are limited awareness, knowledge, and screening opportunities for OSA. Increasing awareness and improving screening strategies for OSA in minorities may alleviate stroke risk burden and improve stroke outcomes in these populations. This review article is intended to highlight the epidemiology, clinical characteristics, pathophysiology, diagnosis, and treatment of OSA in relation to stroke risk, with an emphasis on race-ethnic disparities.

Race/ethnic differences in obstructive sleep apnea risk in patients with acute ischemic strokes in south Florida.

PURPOSE: Obstructive sleep apnea (OSA) is a risk factor for ischemic stroke, but it may differ between race/ethnic groups. The goal of our study was to examine the pre-stroke risk of OSA between three race/ethnic groups admitted for acute ischemic stroke in a tertiary urban hospital in South Florida. METHODS: Our sample was composed of patients with acute ischemic strokes evaluated at a teaching hospital over a 3-year period. Race/ethnicity was defined by self-identification, modeled after the US census and categorized into non-Hispanic whites, non-Hispanic blacks, and Hispanics. Pre-stroke risk of OSA was assessed with the Berlin questionnaire and categorized into high- or low-risk categories. We performed binary logistic regression to evaluate the pre-stroke risk of OSA in Hispanics and non-Hispanic blacks with non-Hispanic whites as the reference, adjusting for age, body mass index, hypertension, diabetes, and smoking. RESULTS: There were 176 patients with acute ischemic strokes of which 44 % were Hispanics, 44 % non-Hispanic Blacks, and 12 % non-Hispanic whites. A higher frequency of patients at high risk for OSA was seen in 60 % of Hispanics, 54 % of non-Hispanic blacks, and 33 % of non-Hispanic whites. Hispanics (OR, 2.6; 95 % CI 1.1-6.4) had a higher frequency of patients at high risk for OSA compared to non-Hispanic whites, adjusting for covariates. There were no differences between non-Hispanic blacks (OR, 1.2; 0.5-2.9 and non-Hispanic whites. DISCUSSION: We observed higher frequency of patients at high risk for OSA in Hispanics with acute ischemic strokes in South Florida.

Vascular Dementia.

The purpose of this review is to highlight existing literature on the epidemiology, pathophysiology, and novel risk factors for vascular dementia. We further examine the evidence linking chronic brain hypoperfusion induced by a variety of cardiovascular diseases to the development of vascular dementia. In the elderly, in whom cerebral perfusion is diminished by the aging process, additional reduction in cerebral blood flow stemming from exposure to potentially modifiable vascular risk factors increases the probability of developing vascular dementia. Finally, we discuss the association between obstructive sleep apnea, an underrecognized risk factor for stroke, and vascular dementia. Obstructive sleep apnea is linked to cerebrovascular disease through many intermediary vascular risk factors and may directly cause cerebrovascular damage through microvacular disease. Insight into how cardiovascular risk factors induce vascular dementia offers an enhanced understanding of the multifactorial pathophysiology by this disorder and ways of preventing and managing the cerebrovascular precursors of vascular dementia. Many vital questions about the relation of obstructive sleep apnea with stroke and vascular dementia are still unanswered and await future well-designed studies.