Poor sleep is increasingly figuring as one of the major culprits in causing neurodegenerative disorders, such as dementia and one of its forms, Alzheimer’s disease.
Researchers led by scientists at the UK’s University of Cambridge undertook a study that has revealed insights into the workings of the brain’s cerebrospinal fluid and its contribution to clearing out waste products like proteins or ‘plaque’.
The cerebrospinal fluid not only helps cushion the central nervous system against shocks, but also nourishes the organ with nutrients and is responsible for removing waste build-up.
The colourless fluid moves through specific perivascular channels when we sleep, called the glymphatic system, to get rid of protein clumps, called amyloid clump-ups, that form toxic plaque.
The study, published in the journal Alzheimer’s and Dementia: The Journal of the Alzheimer’s Association, has found out that an impaired movement of the brain’s cerebrospinal fluid could explain how poor sleep and heart conditions can increase one’s risk of dementia, a neurodegenerative disorder in which memory, speech and thought processes are steadily affected with age, and can eventually disrupt daily activities.
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The study specifically focused on whether a disorder of the brain’s small blood vessels – which affects blood flow and can cause vascular dementia – and cardiovascular risk factors, such as blood pressure, can damage the glymphatic system and increase risk of the brain disorder.
The researchers analysed MRI brain scans of 40,000 adults in the UK Biobank, and found three biomarkers that may help predict one’s risk of dementia over a period of 10 years.
These biomarkers include noting how water spreads along the tiny channels around blood vessels – the perivascular spaces – and the velocity of the cerebrospinal fluid while flowing into the brain.
“Although we have to be cautious about indirect markers, our work provides good evidence in a very large cohort that disruption of the glymphatic system plays a role in dementia. This is exciting because it allows us to ask: how can we improve this?” said Yutong Chen, an author of the study, from the University of Cambridge’s department of clinical neurosciences, said.
The authors said it was clear that “impaired (cerebrospinal fluid) dynamics may lead to dementia and partially mediate cardiovascular risk-dementia associations.”
“We already have evidence that small vessel disease in the brain accelerates diseases like Alzheimer’s, and now we have a likely explanation why. Disruption to the glymphatic system is likely to impair our ability to clear the brain of the amyloid and tau that causes Alzheimer’s disease,” said first author Hui Hong, a radiologist at the Second Affiliated Hospital of Zhejiang University in China, said.
They added, however, that while cardiovascular risk factors, such as blood pressure and diabetes, are thought to contribute to dementia through an impacted flow of the cerebrospinal fluid, evidence from humans is low.
But, besides poor sleep, cardiovascular risk factors did affect the functioning of the glymphatic system, thereby increasing dementia risk – in part by causing cerebral small vessel disease – the researchers found.
The team suggested that good sleep, which is important for the functioning of the glymphatic system, could be a strategy for reducing dementia risk.
There may be existing medicines that could be repurposed, or new ones that could be developed, to improve the glymphatic function, they added.
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