Subjective daytime sleepiness, not sleep quality or hypoxia, predicts sleep-dependent memory consolidation in a cohort of older adults.

STUDY OBJECTIVES

Aging markedly increases the risk of both Alzheimer's disease and obstructive sleep apnea (OSA). Memory deficits, an early indicator of Alzheimer's disease, can be reduced in those of middle age with OSA through treatment, with positive-airway pressure being the first-line treatment standard. Here, we use natural variation in the OSA severity of an older-aged cohort to investigate whether hypoxia or sleep quality predicts sleep-dependent memory consolidation (SDMC).

METHODS

Participants aged 65-85 years not currently receiving OSA treatment were recruited from the San Diego community via advertisement and referrals from other sleep studies. Participants undertook a computerized neurocognitive battery and overnight polysomnography. SDMC was measured using a word-pair associates task. Two linear regression analyses assessed associations between (1) SDMC and hypoxia metrics and (2) SDMC and sleep quality metrics.

RESULTS

The study included 67 participants (36 females, 31 males), most of whom presented with moderate or severe OSA. No significant associations were present in the hypoxia model. A negative association between Epworth Sleepiness Scale score and SDMC was the only significant relationship in the sleep-quality model. There was also a mild univariate correlation between Epworth Sleepiness Scale score and a second daytime function measure, the psychomotor vigilance task.

CONCLUSIONS

Objective measures of OSA pathology including hypoxia and sleep fragmentation were not associated with memory; however, Epworth Sleepiness Scale score, a subjective measure of daytime sleepiness, was associated with poorer memory task performance. This highlights the importance of considering subjective perceptions of sleep quality and daytime function in cognitive health outcomes of patients with OSA, particularly in older adults, in whom the myriad comorbidities that contribute to memory deficits may integrate.

CLINICAL TRIAL REGISTRATION

Registry: ClinicalTrials.gov; Name: Is Obstructive Sleep Apnea Important in the Development of Alzheimer's Disease?; URL: https://clinicaltrials.gov/study/NCT05094271; Identifier: NCT05094271.

CITATION

Harding CD, Holloway BM, DeYoung PN, et al. Subjective daytime sleepiness, not sleep quality or hypoxia, predicts sleep-dependent memory consolidation in a cohort of older adults. 2025;21(7):1217-1226.