When neurons are active in your brain, they create waste
Nick Veasey/Science Photo Library/Alamy
As we enjoy the holiday season, many are already planning a detox for the new year: reducing screen time, perhaps, or abstaining from alcohol. Recently, I wondered if we could apply the same logic to the brain: Is there anything I can do after the fun is over to help clear my cognitive cobwebs?
In fact, the brain performs its own type of detoxification every day – removing waste products generated by metabolism that would otherwise build up and cause damage. But can we help this process? And if so, could it protect us from age-related cognitive decline and dementia?
Let’s start by meeting the brain cleansing team, starting with the glymphatic system. This relatively recently discovered waste elimination pathway “sucks” unwanted proteins and other waste debris from the spaces between your neurons and transports them to the cerebrospinal fluid (CSF).
“CSF circulates like water in a dishwasher,” says Maha Alattar of Virginia Commonwealth University in Richmond.
The fluid then carries the waste into your lymph nodes and from there to the veins, before it is finally excreted from your body.
How the glymphatic and lymphatic systems connect is not particularly well understood, but researchers are increasingly interested in how to optimize the efficiency of the glymphatic system, as they believe it may be important for preventing cognitive decline and maintaining healthy aging. This is partly because a buildup of metabolic waste in the brain is associated with poorer cognitive health, increased risk of dementia, and accelerated symptoms of Alzheimer’s and Parkinson’s disease.
“The glymphatic system is exciting,” says Nandakumar Narayanan of the University of Iowa Health Care. “There are many exciting ideas and research efforts to understand the glymphatic system, measure it rigorously, and use these measurements to better understand human health and disease. »
Stimulate your brain’s waste disposal system
So, is there anything we can do to make this waste disposal system work more efficiently? Recent studies have suggested that lifestyle factors may be our best tools.
“The most well-known way to improve glymphatic clearance is sleep,” says Lila Landowski of the University of Tasmania in Hobart, Australia.
The glymphatic system is largely disengaged during our waking hours and does its best work at night. For example, in mice, CSF flow increases by about 60 percent during sleep, significantly enhancing the elimination of beta-amyloid – the protein associated with Alzheimer’s disease.
Although trials have not yet conclusively proven that strengthening the glymphatic system prevents dementia, “the hypothesis is supported by the fact that factors that reduce glymphatic clearance—sleep disturbances, glymphatic dysfunction, and sedentary lifestyle—are all linked to increased risk of neurodegenerative disease and cognitive impairment,” says Landowski.
Oddly enough, the way you sleep can also contribute to glymphatic drainage. In 2015, Hélène Benveniste, now at the Yale School of Medicine, and colleagues found that sleeping on one’s side improved glymphatic clearance in mice more effectively than sleeping on their back or front. No one has tested this in humans yet, but because many types of dementia are closely linked to sleep disorders, Benveniste and his team propose that the way you sleep could prove to be a useful part of our arsenal against dementia.
Other ways to drain your brain
Growing evidence suggests that other lifestyle factors, such as exercise, also boost glymphatic function. In April, 37 adults underwent brain imaging before and after participating in either a single workout or a 12-week stationary cycling program, including 30-minute sessions three times a week. Only the group that exercised for 12 weeks showed an increase in lymphatic drainage.
“Studies in mice show that glymphatic clearance approximately doubles after 5 weeks of exercise compared to sedentary mice,” says Landowski, “but shorter time frames have not yet been studied in humans.”
But a closer look at the glymphatic system could reveal other ways to improve its flow. The lymphatic vessels that drain CSF lie deep in the neck, making them difficult to manipulate directly, but recently Gou Young Koh of the Korea Advanced Institute of Science and Technology in South Korea and colleagues discovered another network of lymphatic vessels just under the skin on the faces and necks of monkeys and mice.
In mice, gently stroking the face and neck for one minute increased CSF flow threefold, effectively restoring the reduced flow seen in older animals to a more youthful state.
Similar vessels have been found in human cadavers, raising the possibility that facial or neck massage may also increase CSF flow in us and, in doing so, contribute to glymphatic clearance, but further research is needed to determine whether this occurs and whether this increased flow may protect against neurodegenerative diseases.
The solid evidence for yogic breathing
One type of exercise you don’t want to neglect is yogic breathing, says Hamid Djalilian of the University of California, Irvine. There is now well-documented evidence that diaphragmatic breathing can increase CSF velocity, which Djalilian says is enough to trigger the glymphatic “flush cycle.”
Diaphragmatic breathing is a deep breathing technique in which you inhale through your nose while moving your stomach outward to lower your diaphragm while the chest remains relatively still. Exhaling through pursed lips while rolling your stomach inward completes the cycle.
Unexplored potential
However, despite the enthusiasm of some researchers, our understanding of the complex workings of the glymphatic system is still in its infancy, and not everyone yet thinks we know enough to actively prescribe interventions. “We are certainly not at the level where we can predict how specific interventions such as exercise affect the glymphatic system. There are a few studies in mice and small groups of humans, but not a large definitive study,” warns Narayanan.
But even he is optimistic. “The potential is enormous, but we must conduct these studies with care and rigor. »
So for now, I’m going to focus on the things I should be doing anyway: sleeping well and exercising regularly. These habits are already important for overall health, but if glymphatic research bears this out, they could prove even more important for keeping my brain clear not only in the new year, but well into the future.
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