NEW YORK, NY, October 7, 2026 — For years scientists have been trying to figure out how the brain gets rid of all of its excess waste products that build up after daily activity. Recent research is challenging the assumption, or at least complicating it: sleep in and of itself may not be up to the task. As it turns out, however, exercise may play an even bigger role than once thought.
Discovering the Brain’s Cleanup System
Cerebrospinal fluid flows through a network known as the glymphatic system, which is how the brain gets rid of waste. This system was discovered over a decade ago by researchers at the University of Rochester Medical Center. They found that liquid flows through the brain, taking away molecules related to cognitive impairment.
Scientists had long thought that this cleanup process was most efficient while we were in deep sleep, when brain cells shrink to allow for greater flow of the fluid. It was that theory which dominated so much mainstream discussion of sleep and brain health. However, newer data has made that simplistic picture a lot more complicated.
Exercise Enters the Picture
A review in the journal Trends in Neurosciences earlier this year evaluated how physical activity may modulate glymphatic function. In the study, researchers led by James Broatch at Victoria University found that exercise could boost waste clearance through a number of interconnected pathways. Enhanced blood-vessel health and lower inflammation both seemed to promote the brain’s cleaning up process.
Exercise may also enhance the quality of deep sleep itself, providing an additional benefit for overnight waste clearance. The association suggests that physical activity and sleep do not work in isolation from one another. However, the majority of evidence still originates from testing in animals rather than humans itself, researchers noted.
An Unexpected Offshoot Of Different Research
Needless to say, sleep is the time when clearance does its best work — or so researchers had long assumed until scientists at Imperial College London’s UK Dementia Research Institute upended this belief just last week. In one study, researchers labeled fluorescent dye in mice to trace how fast the brain clears waste during sleeping and waking states. The time that clearance seemed most efficient was when the mice were awake and moving — not while they were sleeping.
The study’s leaders were quick to note that mouse findings do not necessarily relate directly to humans. Yet sleep is still essential for brain health for more than waste clearance, they noted. Nonetheless, the study contributes to a growing perception that physical activity plays an underestimated role in defending cognitive function.
What This Means for Day-to-Day Habits
The precise route remains debated, but most experts dutifully tend to a consensus that both adequate sleep and a high level of regular physical activity are good for the brain in the long term. Mixing the two habits may give older adults the biggest bang for their buck, as glymphatic function routes waste during sleep and are thought to weaken with age. Current evidence suggests that neither sleep nor exercise alone is enough.
The researchers caution that much more human research is needed before recommendations can be made for specific exercise or sleep regimens to prevent dementia. Meanwhile, sticking to exercise habits in conjunction with sound sleep is at least the most widely endorsed method for now. Scientists are working on developing more accurate ways of recording glymphatic activity directly from inside living human brains.
In animal studies of amyloid-beta clearance — the protein closely associated with Alzheimer’s disease — aerobic activity in particular has captured interest. Glymphatic clearance of this protein appears to be enhanced by aerobic exercise in mouse models. Whether the same advantage translates consistently in humans is a subject of continued inquiry.
Expert studies advise at least 150 minutes of moderate aerobic activity weekly for overall well-being, a target that aligns with broader cardiovascular recommendations supported by the American Heart Association. Current research trends suggest that the same level of activity may also provide other advantages concerning the clearance of brain waste. Movement in combination with a rhythm of sleep appears to be the best all-around prophylactic that we have.
As scientists learn more about glymphatic research and its connection to aging and cognitive decline, funding for such work has grown significantly. Multiple clinical trials are currently registered with the National Institutes of Health to assess glymphatic function in healthy humans using state-of-the-art imaging modalities. Results from those studies may lead to more targeted public health recommendations.
