The clinical importance of obstructive sleep apnea in Alzheimers disease

Abstract

Recent findings suggest that obstructive sleep apnea (OSA) is very common and underdiagnosed in the early stages of dementia and Alzheimer’s disease (AD). The objective of this study was to assess the prevalence and nightly variance in OSA in mild AD patients in relation to repeated assessments of cognitive function and neuropsychiatric symptoms. Twenty mild AD patients (mini-mental state examination [MMSE] >20; age 45–80 years), over a time period of four weeks, underwent a home type 3 sleep study including pulse oximetry, assessment of respiratory effort, airflow, body position and movement. CogState computerized cognitive assessments and the psychomotor vigilance test (PVT) were performed each morning following the sleep assessments to measure visual memory, attention/vigilance and working memory. Participants additionally completed the Epworth Sleepiness Scale and the Neuropsychiatric Inventory (NPI) was administered to their caregivers. The preliminary results showed an OSA prevalence of 90% (AHI¡Ý5) and an average (¡ÀSD) AHI of 13.0 (¡À5.7) events/hour over 5 assessments (12 patients had mild OSA, 3 moderate and 3 severe OSA). Substantial nightly fluctuations in OSA were seen with an average AHI fluctuation of 13.4 (¡À9.9) events/hour. Moreover, patients with an average AHI¡Ý10 ( n = 10 subjects) performed significantly worse on a test of visual attention/vigilance and presented with more apathy as a neuropsychiatric symptom than patients with an average AHI < 10 ( n = 10 subjects). However, no differences were found in other cognitive tests performed or in the PVT performance and only 5% of patients reported excessive daytime sleepiness (Epworth Sleepiness Scale ¡Ý10). OSA appears be underdiagnosed in AD and repeated assessments may lead to a more accurate diagnosis of OSA due to the nightly fluctuations in OSA severity. Preliminary findings suggest that cognition and neuropsychiatric symptoms in AD patients may be adversely affected by increased severity of OSA. Also, subjective reporting of sleepiness may not be suitable to screen for OSA in AD patients. Further studies are warranted to better understand the effects of OSA and its treatment on the clinical symptomatology of AD. Grant support from AstraZeneca.