Can you wash your brain? How glymphatic system protects against cognitive decline

The brain produces waste products and toxins as part of its daily workload. Scientists now know these can be flushed away by an internal disposal pathway called the glymphatic system, which helps protect against cognitive diseases such as Alzheimer's and Parkinson's.

Danish neuroscientists discovered the system in 2012, and it has since become a major focus of research. Roslyn Bill, professor of biotechnology and director of the Institute for Membrane Excellence at Aston University, said the lymphatic system's role in eliminating toxins from the body has long been known, but a similar mechanism in the brain was identified only recently.

According to Bill, the system flushes cerebrospinal fluid (CSF), a clear liquid, through the brain via channels called perivascular spaces. Blood vessels swell and constrict to pump the fluid around, washing away unwanted proteins and by-products of cellular metabolism. She likened it to a sluicing system used to clean block paving on a patio. She added that it works more effectively at night, when the brain is not working as hard because the person is asleep.

Bill said the system becomes less efficient with age. Arteries stiffen, fluid pumping slows, and toxins are not washed away as effectively. Among these waste products is amyloid beta protein (Aβ), which is associated with Alzheimer's disease when deposited in the brain. It forms clumps called plaques which, along with tau protein tangles in brain cells, are key hallmarks of dementia.

A study of 40,000 UK adults, published last year in Alzheimer's & Dementia: The Journal of the Alzheimer's Association, found that impaired movement of CSF predicted dementia risk later in life. Hui Hong, a radiologist and the paper's lead author, said small vessel disease in the brain was already known to accelerate diseases such as Alzheimer's, and the findings offer a likely explanation. "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," Hong told news outlet The Times.

Emerging research also suggests a sluggish glymphatic system may be linked to other conditions, including Parkinson's. Bill said treatments to maintain glymphatic function are being developed. She and her colleagues are in the early stages of developing what she described as a "statin for the brain" to help clear brain waste with age. She said it could restore blood vessels to their youthful ability to pump well and perhaps delay neurodegeneration.

Other scientists are studying the effects of infrared light helmets and ultrasound techniques on glymphatic fluid flow, though Bill said these therapies are at a very early stage of research. She said researchers are starting to be able to measure, through biomarkers, whether such approaches are working to clear waste products from the brain.

Bill said some lifestyle habits are known to help prevent the glymphatic system from slowing down.