Alzheimer’s Study: Sleep Apnea During REM Stage Linked to Memory Decline

Researchers from the University of California, Irvine, discovered that sleep apnea severity during the REM stage of sleep negatively impacts verbal memory. According to the researchers, the adverse effect is particularly severe among older persons at risk for Alzheimer’s.

Obstructive sleep apnea (OSA) is a disorder in which an individual has breathing pauses or interruptions during sleep. Researchers estimate that approximately 936 million people worldwide suffer from this condition [1].

Previous research has connected OSA to an increased risk for various neurological disorders, including cognitive decline, dementia [2], Parkinson’s disease [3], and Alzheimer’s disease [4].

Researchers at the University of California have now discovered that verbal memory is adversely affected by the severity of sleep apnea during the rapid eye movement (REM) stage of sleep, particularly in older persons who are at a higher risk of developing Alzheimer’s. The journal Alzheimer’s Research & Therapy recently published this research [5].

What is Verbal Memory?

Verbal memory was the primary focus of this study. According to Bryce A. Mander, PhD, associate professor in the Department of Psychiatry and Human Behavior at the University of California and co-corresponding author of this study, verbal memory refers to the capability to remember words in the appropriate context.

Examples of verbal memory include remembering someone’s name, the names of streets at an intersection connected to a memory, and how words are paired together.

He further stated that verbal memory is very vulnerable to Alzheimer’s and is one of the initial types of memory to be affected by the condition’s biomarkers. Its susceptibility to deterioration with age and Alzheimer’s led researchers to study this type of memory.

Effect of sleep apnea during REM sleep on verbal memory

The recent study included 81 individuals with an average age of roughly 62, and 70% of them had a parental history of Alzheimer’s. The group had 62% female participants. Every study participant underwent verbal memory tests and polysomnography, a diagnostic procedure for sleep disorders.

At the end of the study, researchers discovered that REM sleep apnea episodes have a detrimental effect on a person’s verbal memory, particularly in those participants who have a family history of Alzheimer’s or a genetic susceptibility to the condition.

The researchers initially hypothesized that events in non-rapid eye movement (NREM) sleep would be more predictive since some specific brain waves occur only during NREM sleep support memory.

However, they believe these REM findings make sense because REM sleep may aid memory and has a higher metabolic requirement than NREM sleep, and in some memory-related brain areas, even higher than when awake.

Mander noted that if you deprive your brain of oxygen during high metabolic demand, you may be more prone to sustaining brain damage. The team is looking into this possibility for their upcoming studies.

Possibility of sleep apnea-related Alzheimer’s treatment

These findings highlight the potential impact of sleep apnea occurrences during REM sleep. They are frequently rejected clinically in favor of global sleep apnea metrics, which have historically been poor at predicting cognitive and health effects.

These findings support the notion that studying the brain state in which sleep apnea occurs will provide a better understanding of the cognitive implications of sleep apnea.

Additionally, the researchers believe that this may emphasize how crucial it is to concentrate on how sleep apnea severity is measured when examining the health and neurodegenerative impacts of Alzheimer’s, as well as how sleep apnea treatment may be tailored to reduce the cognitive effects of the disease.

Mander further stated that although OSA is a known risk factor for Alzheimer’s, it is unclear which features of the condition are significant for the cognitive impairment linked to the illness’s risk. Finding these particular connections is essential to comprehend the reasons why sleep apnea is associated with a higher risk of dementia and to develop treatment plans that specifically address the processes underlying this correlation.

Mander said that their research demonstrated the complex connection between memory loss, sleep apnea, and the risk of Alzheimer’s disease. Identifying and responding to REM-specific events is critical for establishing proactive, tailored approaches to assessment and therapy based on individual sleep patterns.

References

1. Sleep Apnea Statistics and Facts You Should Know. National Council on Aging. https://www.ncoa.org/adviser/sleep/sleep-apnea-statistics/. Published Online: 8th May, 2024. Accessed: 1st July, 2024.
2. Guay‐Gagnon, M., Vat, S., Forget, M.F., Tremblay‐Gravel, M., Ducharme, S., Nguyen, Q.D. and Desmarais, P., 2022. Sleep apnea and the risk of dementia: A systematic review and meta‐analysis. Journal of sleep research, 31(5), p.e13589.
3. Yu, Q., Hu, X., Zheng, T., Liu, L., Kuang, G., Liu, H., Wang, X., Li, J., Huang, J., Wang, T. and Lin, Z., 2023. Obstructive sleep apnea in Parkinson’s disease: A prevalent, clinically relevant and treatable feature. Parkinsonism & Related Disorders, p.105790.
4. Tsai, M.S., Li, H.Y., Huang, C.G., Wang, R.Y., Chuang, L.P., Chen, N.H., Liu, C.H., Yang, Y.H., Liu, C.Y., Hsu, C.M. and Cheng, W.N., 2020. Risk of Alzheimer’s disease in obstructive sleep apnea patients with or without treatment: real‐world evidence. The Laryngoscope, 130(9), pp.2292-2298.
5. Lui, K.K., Dave, A., Sprecher, K.E., Chappel-Farley, M.G., Riedner, B.A., Heston, M.B., Taylor, C.E., Carlsson, C.M., Okonkwo, O.C., Asthana, S. and Johnson, S.C., 2024. Older adults at greater risk for Alzheimer’s disease show stronger associations between sleep apnea severity in REM sleep and verbal memory. Alzheimer’s Research & Therapy, 16(1), p.102.
6. Obstructive sleep apnea during REM stage linked to memory decline. Medical News Today. https://www.medicalnewstoday.com/articles/sleep-apnea-severity-rem-sleep-memory-decline. Published Online: 21st May, 2024. Accessed: 1st July, 2024.
7. Study links sleep apnea severity during REM stage to verbal memory decline. ScienceDaily. https://www.sciencedaily.com/releases/2024/05/240514183457.htm. Published Online: 14th May, 2024. Accessed: 1st July, 2024.