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Measures of Cognitive Function in Persons with Varying Degrees of
Sleep-Disordered Breathing:
The Sleep Heart Health Study.
ABSTRACT
Summary: Epidemiologic literature suggests that persons with clinically
diagnosed sleep apnoea frequently have impaired cognitive function, but whether milder degrees of
sleep-disordered breathing (SDB) are associated with cognitive dysfunction in the general population is
largely unknown. Approximately 1700 subjects free of clinically diagnosed SDB underwent at-home
polysomnography (PSG) as part of the Sleep Heart Health Study (SHHS) and completed three cognitive
function tests within 1–2 years of their PSG: the Delayed Word Recall Test (DWR), the WAIS-R Digit
Symbol Subtest (DSS), and the Word Fluency test (WF). A respiratory disturbance index (RDI) was calculated
as the number of apnoeas and hypopnoeas per hour of sleep. After adjustment for age, education, occupation,
field centre, diabetes, hypertension, body-mass index, use of CNS medications, and alcohol drinking status,
there was no consistent association between the RDI and any of the three cognitive function measures. There
was no evidence of a dose–response relation between the RDI and cognitive function scores and the adjusted
mean scores by quartiles of RDI never differed from one another by more than 5% for any of the tests. In
this sample of free-living individuals with mostly mild to moderate levels of SDB, the degree of SDB appeared
to be unrelated to three measures of cognitive performance.
