Admit it – while we all know how important sleep is, most of us do take it for granted. We just sometimes get too wrapped up in life and work that we often deprive our bodies of the rest it needs. We don’t really think too much about it until we see and feel the repercussions later on in life. Ask anyone who belongs to the older echelon of society, and they can explain how health declines with previous habits.
Sleep is an extremely important activity. In fact, a new study links sleep-dependent brain activity with the excretion of toxic proteins that are connected to Alzheimer’s disease. More importantly, this activity seems to weaken in the brains of those with a higher risk of cognitive decline. As sad as this fact may be, the recent discoveries could provide a potential biomarker when it comes to diagnosing neurodegenerative diseases.
A recent research has been published in PLOS Biology. The findings suggest that global brain activity during deep sleep could actually decrease Alzheimer’s-related toxin buildup. This recent discovery validates the previous findings that indicate how low frequency brain waves produced during the non-rapid eye movement (NREM) sleep phase plays a crucial part in cleaning the brain from toxic waste. Leading the study is Dr. Xiao Liu, assistant professor of biomedical engineering at the Pennsylvania State University.
The Connection between the Glymphatic System and Alzheimer’s Disease
This somewhat debilitating disease develops when there is an increase in the levels of the proteins amyloid-β (Aβ) and tau in the brain. Extensive research has been made and the findings suggest how these substances are major contributors to cognitive deterioration.
It takes time for the symptoms of Alzheimer’s to manifest, but when it does, it’s because the toxic buildup has advanced drastically. This accumulation could actually start long before. Experts say that it may be as far as 10 to 20 years before the actual onset of the symptoms of dementia. That’s because many of the health experts believe that cerebrospinal fluid (CSF) carries so much waste products away from the brain through the glymphatic system – the system of channels found in the central nervous system.
The glial cells make up a substantial amount of the brain’s total mass. These work in collaboration with blood vessels to help shield neurons from physical and chemical damage. According to a 2021 review made, impairments in glymphatic draining could lead to an extracellular buildup of waste products that stay in the brain. As a result, this could breed unfavorable conditions in the central nervous system. The buildup could then result to neurodegenerative diseases, one of which is Alzheimer’s disease.
The Protective Potential of Deep Sleep
There has been a growing bodies of research made about sleep and Alzheimer’s. Many of them show how deep sleep could actually help the brain wash away the Alzheimer’s-related toxins that accumulates. During the NREM stage, the brain’s slow, steady electrical waves serve as somewhat of a cleaning mechanism that sweeps it all away.
A 2019 review was made and the results show how large low frequency brain waves occur just before a pulse of CSF floods through the areas of the brain. The study state how these “oscillations in neural activity support memory consolidation and neuronal computation.” These flows of fluid occur on a much broader scale during deep rest. They compared the numbers during wakefulness and there was a significant difference.
Dr. Liu and his colleagues wanted to conduct further investigations on this phenomenon. They decided to study 118 subjects from the Alzheimer’s Disease Neuroimaging Initiative. The participants were comprised of “7 [patients with Alzheimer’s disease], 62 [patients with mild cognitive impairment], 18 significant memory concern […] patients, and 31 healthy controls.”
The 118 participants then underwent resting-state functional MRI sessions that were spaced 2 years apart. The scientists and researchers then probed into the global brain activity and CSF flow in addition to the behavioral data they had. They compared their assessments with the Alzheimer’s-associated markers such as CSF flow, Aβ levels, and behaviors.
Faulty Coupling
The findings were made and they found that the participants with a higher risk of Alzheimer’s disease and those who had already developed the disease, in fact, exhibited a weaker connection between brain activity and CSF flow. This so-called defective connection was also correlated to the higher Aβ levels and Alzheimer’s-related behavioral patterns after 2 years.
Dr. Liu explained, “The study linked the coupling between the resting-state global brain activity and [CSF] flow to Alzheimer’s disease pathology. The finding highlights the potential role of low frequency (less than 0.1 [hertz]) resting-state neural and physiological dynamics in the neurodegenerative diseases, presumably due to their sleep-dependent driving of [CSF] flow to wash out brain toxins.”
Hence, they came to the conclusion that the coupling was significantly weaker in female and older participants, all of whom had a higher risk of developing the disease.
The Mounting Evidence of Sleep and Alzheimer’s Connection
The current study concurs with the earlier studies made. All these have connected sleep with Alzheimer’s disease progression. In 2018, a group of researchers discovered that just 1 night of being deprived of sleep already increases the Aβ burden found in the brain. Then, in a 2019 clinical trial that involved cognitively healthy individuals, the NREM sleep negatively correlated with Aβ deposits and tau protein that clumped in the different regions of the brain. With the findings made, the authors of the study made a recommendation. They said that sleep analysis could actually aid in the early detection of Alzheimer’s disease.
Unfortunately, as with many case studies, the current study does have certain limitations. For example, this one only involved a limited sample size and a relatively short time frame. Moreover, the authors stressed the fact that the results they had cannot definitively prove a causal relationship. As Dr. Liu explained, “Future studies are warranted to fully understand the global brain activity and associated physiological modulations and their role in glymphatic clearance and neurodegenerative diseases.”
Current Implications of the Study Made
The analysis the authors made highlights how deeply sleep quality can impact not just the overall health of the person, but the brain health as well. While there has been no categorical conclusions made just yet, sleep activity could prove to be a very telling marker for risk of cognitive decline. Thus, this could increase the chances of early intervention for the health experts and doctors everywhere.
Medical News Today asked Dr. Arthur Toga, a neuroscientist at the University of California’s Keck School of Medicine in Los Angeles, about this and talked about the significance of this study. He said, “This work is an important contribution to our understanding of the mechanisms involved in clearing toxins from the brain. There are several mechanisms that may contribute, including dysregulation of the blood-brain barrier and changes in the glymphatic system. […] The roles of sleep, the glymphatic system, CSF, and perivascular spaces in the clearance of amyloid and tau are not fully understood, and this paper brings us one step closer.”
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