A recent pilot clinical study suggests a significant correlation between the latency of REM sleep and biomarkers indicative of Alzheimer's disease. Conducted with 128 participants aged 50 and older, all of whom are of Han Chinese descent, the study highlights the potential for REM sleep latency to serve as an early marker for Alzheimer's disease and related dementias.
During the study, participants' sleep patterns were monitored for a single night. While this approach provided valuable initial insights, researchers acknowledge that one night's observation may not accurately reflect an individual's typical sleep behavior. Notably, the study revealed that those with longer REM sleep latency exhibited higher levels of phosphorylated tau at threonine 181 (p-tau 181) and amyloid beta, both established biomarkers for Alzheimer's disease.
Furthermore, the research found that participants displaying prolonged REM sleep latency had lower levels of plasma brain-derived neurotrophic factor (BDNF), a protein crucial for maintaining brain health. These findings were consistent regardless of participants' cognitive status or their APOE ε4 genetic risk factor associated with Alzheimer's disease.
Among the participants, sixty-four had been diagnosed with Alzheimer's disease, while forty-one exhibited mild cognitive impairment. The remaining participants demonstrated normal cognitive function. The results indicate that REM sleep latency could be a useful marker for identifying Alzheimer's disease and related dementias.
Giulio Taglialatela, PhD, a key researcher in the study, noted the significance of the findings. He stated, “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.” This comment underscores the potential implications of REM sleep latency in understanding Alzheimer's disease.
The study's findings shift previous research focus from slow-wave sleep to REM sleep, emphasizing the importance of all stages of the sleep cycle in relation to Alzheimer's disease. Dr. Taglialatela elaborated on this shift, stating, “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.”
The correlation between sleep patterns and the risk of developing dementia has been recognized in earlier studies. However, this research identifies a specific perturbation—delayed first REM episode—that could help illuminate the complexity of the sleep-dementia connection. Dr. Taglialatela remarked, “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.”
While the findings present a promising avenue for further exploration, it is important to note that the National Institute of Neurological Disorders and Stroke has indicated that the relationship between REM sleep latency and Alzheimer's disease has not yet been established as causal. Despite this uncertainty, Dr. Taglialatela emphasized the potential significance of tracking REM sleep latency: “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.”
He continued by cautioning that more research is essential to fully understand the biological underpinnings of REM sleep latency and its implications for Alzheimer's disease. “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].”
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