Obstructive sleep apnea occurring during rapid eye movement sleep was associated with worse performance on verbal memory tests in middle-aged and older adults at increased risk for Alzheimer's disease, researchers reported.
The study, published in Alzheimer's Research & Therapy, suggested that obstructive sleep apnea (OSA) during rapid eye movement (REM) sleep may be associated with memory function in individuals with multiple Alzheimer's disease (AD) risk factors.
The study included 81 cognitively unimpaired adults with a mean age of 61.7 years, 62% of whom were female. Among the participants, 32% carried the apolipoprotein E ε4 allele (APOE4), a genetic risk factor for AD, and 70% had a parental history of AD. All participants underwent clinical polysomnography to assess OSA severity and completed the Rey Auditory Verbal Learning Test (RAVLT) to evaluate verbal memory.
The researchers found that greater OSA severity during REM sleep, as measured by the apnea-hypopnea index (AHI), respiratory disturbance index (RDI), and oxyhemoglobin desaturation index (ODI), was associated with lower scores on RAVLT total learning and long-delay recall. In contrast, OSA severity during non-REM (NREM) sleep was not significantly associated with verbal memory performance.
Furthermore, the study revealed that the negative impact of REM sleep OSA on verbal memory was more pronounced in older adults and individuals with both genetic and parental risk for AD. Specifically, the association between REM ODI and total learning was driven by adults aged 60 years and older, while the associations between REM-NREM ODI ratio and total learning, as well as REM-NREM RDI ratio and long-delay recall, were primarily observed in APOE4 carriers.
OSA may be a modifiable risk factor for AD highlighting the importance of early diagnosis and effective treatment, particularly in older adults and those with genetic and familial risk for AD. The researchers suggested that aggressive OSA treatment covering the entire sleep period may help mitigate cognitive impairment and reduce the risk for AD in individuals with OSA.
However, the study had some limitations, including its cross-sectional design and relatively small sample size. Further longitudinal studies are needed to examine the effects of OSA treatment on memory decline and progression to mild cognitive impairment or AD.
The authors declared no conflicts of interest.
