Obstructive sleep apnoea (OSA), a condition marked by repeated interruptions in breathing during sleep, has been linked to changes in brain regions responsible for memory, according to a study published on 7 May 2025 in Neurology®, the medical journal of the American Academy of Neurology. The research suggests that the drops in oxygen levels caused by OSA—particularly during rapid eye movement (REM) sleep—may lead to the degeneration of memory-related brain structures through damage to the brain’s small blood vessels. Notably, the study reveals a strong association rather than a direct causal relationship, indicating that more investigation is needed to determine whether OSA actively causes these neurological changes.
OSA typically occurs when the muscles in the throat relax during sleep, temporarily blocking the upper airway. This disruption often causes individuals to wake repeatedly to resume breathing. Such fragmented sleep results in lowered blood oxygen levels, and over time, these episodes of hypoxia can harm the delicate microvascular structures in the brain. Damage to these small blood vessels is known to impair white matter integrity and may initiate or exacerbate cognitive decline. While sleep apnoea is known to increase in prevalence with age, its potential role in accelerating neurodegeneration has become a growing focus of research.
REM sleep is especially significant in this context, as it is the stage of sleep most closely associated with dreaming, emotional processing, and memory consolidation. According to Dr Bryce A. Mander of the University of California, Irvine, who led the study, the findings suggest that low oxygen levels during REM sleep may be particularly harmful in cognitive decline. By examining the relationship between oxygen saturation and brain health, the research contributes to a deeper understanding of how OSA might impair neural function—particularly in brain areas vital for memory, such as the hippocampus and the entorhinal cortex.
The study involved 37 older adults, with an average age of 73, none of whom had been diagnosed with cognitive impairment or were using sleep medications. Each participant underwent overnight polysomnography, a comprehensive sleep study that measured various physiological parameters, including blood oxygen levels throughout different stages of sleep. Brain imaging was also conducted using high-resolution scans to assess white and grey matter structures. Of the participants, 24 were diagnosed with obstructive sleep apnoea, allowing researchers to compare brain changes between those with and without the condition.
One of the study’s key findings was the association between oxygen desaturation during REM sleep and increased volumes of white matter hyperintensities—lesions that appear as bright spots on MRI scans and are considered markers of small vessel disease. The researchers also found that the lowest oxygen saturation levels and time spent below 90% blood oxygen saturation during sleep predicted the extent of white matter hyperintensities. Further analysis revealed that these lesions were linked to a reduced hippocampus volume and a thinner entorhinal cortex. These structural changes, in turn, were associated with poorer performance on memory tasks, suggesting a possible pathway from sleep-related hypoxia to cognitive impairment.
While the results provide compelling evidence for an association between sleep apnoea and neurodegeneration, the authors caution that the study has limitations. Chief among them is the relatively small sample size and the lack of ethnic diversity, as most participants were either white or Asian. This limits the ability to generalise the findings across broader populations. Nonetheless, the study contributes to a growing body of literature that connects untreated sleep apnoea with age-related cognitive decline and diseases such as Alzheimer’s. The findings underscore the importance of early diagnosis and management of sleep apnoea to improve sleep quality and potentially protect long-term brain health.
More information: Bryce A. Mander et al, Association of Hypoxemia Due to Obstructive Sleep Apnea With White Matter Hyperintensities and Temporal Lobe Changes in Older Adults, Neurology. DOI: 10.1212/WNL.0000000000213639
Journal information: Neurology Provided by American Academy of Neurology
