- Alzheimer’s disease and Alzheimer’s disease-related dementias are complex disorders that currently have no cure.
- Experts are interested in understanding the relationship between how sleep may affect Alzheimer’s disease.
- One study suggests that taking longer to reach the rapid eye movement (REM) stage of sleep is associated with biomarkers of Alzheimer’s disease.
- The delay in getting to REM might be useful in identifying Alzheimer’s disease and related dementias, or it may be a risk factor for these conditions, the study suggests.
Sleep is essential to physical and mental well-being. Experts are interested in understanding how sleep may affect or be affected by certain conditions, like dementia.
One
The study found that taking longer to reach REM sleep was associated with key plasma biomarkers related to Alzheimer’s disease.
The
The authors of the current study wanted to understand more about the timing of REM sleep and its relationship to Alzheimer’s disease and Alzheimer’s disease and related dementias. is a stage in the sleep cycle when vivid dreaming occurs. REM sleep helps with information processing and consolidation.
For this study, researchers examined REM sleep, and several biomarkers researchers noted were associated with Alzheimer’s disease and Alzheimer’s disease and related dementias.
This research included 128 participants. Sixty-four of the participants had Alzheimer’s disease, forty-one had mild cognitive impairment, and the rest had normal cognition. All participants were at least fifty years old. Aside from Alzheimer’s disease, researchers excluded participants who had other neurodegenerative disorders like Parkinson’s disease. They also had several other exclusion criteria, such as sleep-related movement disorders or the use of antipsychotic drugs.
Researchers collected data on participants’ medical histories, and all participants underwent cranial MRIs, bloodwork, and a number of cognitive tests before the start of the study.
Participants did an overnight sleep study called polysomnography, which can examine brain waves and other physical functions like eye movement and breathing during sleep. Researchers were able to identify when participants’ REM sleep occurred.
Participants underwent PET scans to look at
Researchers also conducted statistical analyses, adjusting for factors like body mass index, sex, and diabetes mellitus. They also adjusted for
How delayed REM sleep affects the brain
The study’s results revealed that participants with the longest REML had higher levels of p-tau181 and amyloid beta and lower levels of plasma brain-derived neurotrophic factor compared to participants with the shortest REML. These results were independent of participants’ cognitive status or APOE ε4 status.
Even after adjusting for the possibility of false positive results, the link between amyloid beta and plasma brain-derived neurotrophic factor — a protein involved in brain cell growth — remained significant. This suggests a meaningful link between these two factors that could be significant for understanding Alzheimer’s disease.
Additionally, having less REM sleep and deep sleep (also known as slow-wave sleep) was linked to higher levels of p-tau181, a protein associated with certain neurological conditions such as Alzheimer’s. Slow-wave sleep is the stage of sleep when people experience the deepest rest. However, this association did not remain significant after considering the possibility of false results.
Study author Yue Leng, PhD, associate professor at the Department of Psychiatry and Behavioral Sciences, Bakar Computational Health Sciences Institute (BCHSI), University of California, San Francisco, noted the following to Medical News Today:
“REM sleep, especially the time it takes to enter REM sleep, is potentially important for Alzheimer’s disease. The importance of this sleep metric has been largely ignored previously. We don’t know if the correlation is causal, but REM sleep latency can potentially serve as a marker and help with the early detection of AD [Alzheimer’s disease]. More research is needed to understand the biological underpinnings of REM sleep latency and its implications for AD (if the relationship is causal).”
This research has a few limitations. First, it cannot establish that delayed REM sleep is a cause of Alzheimer’s disease. Since it was cross-sectional, it also cannot note the direction of the associations it identified.
It also included a fairly small number of participants, all Han Chinese and at least fifty or older. The number of participants in each diagnosis group was also small, and this could have limited the true statistical power needed to compare “associations by cognitive diagnoses.”
While researchers did find that participants with mild cognitive impairment or Alzheimer’s disease took longer to get to REM sleep than participants without cognitive impairment, those results did not reach a statistically significant level.
Future research could benefit from studies with larger sample sizes and greater diversity, as well as from including younger participants.
Researchers also chose to focus on plasma p-tau 181 instead of p-tau217. They note that p-tau217 is more sensitive to predicting Alzheimer’s disease progression.
The setting for the sleep study could have led to environmental disturbances, which could have affected sleep measurement accuracy. Additionally, since the sleep study was only one night, it might not totally reflect what participants’ sleep patterns typically look like. Researchers also note that many participants did not have a percentage of sleep time that was slow-wave sleep, and this could affect the ability to generalize the results.
One of the study authors declared conflicts of interest, and the study received funding support from two grants.
Giulio Taglialatela, PhD, Vice President of Brain Health, Director of the Moody Brain Health Institute, research professor, and the Lawrence J. Del Papa Distinguished Chair in Neurodegenerative Disease Research Professor with the UTMB Department of Neurology, who was not involved in the study, noted the following about the study’s findings:
“[It is] a well-conducted pilot clinical study that suggests that the delay to the first REM episode is associated with increased Alzheimer’s Disease biomarkers. While the observation is interesting and deserving further development, the current study is on a limited number of patients, compromising its full statistical power.”
This study highlights how REM sleep is likely also important when it comes to dementia research and not just slow-wave sleep.
Alex Dimitriu, MD, double board certified in Psychiatry and Sleep Medicine and founder of Menlo Park Psychiatry & Sleep Medicine, who was also not involved in the study, noted:
“The findings in this paper shift the focus from slow-wave sleep to REM sleep as another area of research in Alzheimer’s disease. More generally, these findings add weight to the importance of all stages of our sleep cycle, including REM sleep.”
Overall, more research is required to understand the full clinical implications of the data. However, it’s possible that addressing prolonged REML could potentially modify the risk for Alzheimer’s disease and Alzheimer’s disease and related dementias. Identifying prolonged REML could also help with certain dementia detection early on.
“Relationships between sleep patterns and risk of developing dementia have been noted in the past. This study points to a specific perturbation (delayed first REM episode), shedding some light on the specificity of sleep/dementia connection. Monitoring delayed first REM episodes may represent a marker to predict later development of dementia. However, many more studies are needed to bring this observation to clinical relevance.”
— Giulio Taglialatela, PhD
