New research indicates physical activity, rather than sleep, may play a more crucial role in maintaining brain health by facilitating the removal of toxins, challenging the traditional view that sleep primarily serves to cleanse the brain of harmful substances.

Researchers from the U.K. Dementia Research Institute at Imperial College London have conducted an innovative study using fluorescent dye to monitor the movement and clearance of fluids within the brains of mice. Their findings suggest that the process of flushing out waste materials significantly slows down during sleep or under anesthesia.

“The field has been so focused on the clearance idea as one of the key reasons why we sleep, and we were of course very surprised to observe the opposite in our results,” said study co-lead author Nick Franks, professor of biophysics and anesthetics at Imperial College London. “As yet, we do not know what it is about these states that slows down the removal of molecules from the brain.”

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The study showed a substantial decrease in the efficiency of this cleansing process during rest periods. Specifically, the clearance rate of the dye dropped by approximately 30% in sleeping mice and an even more considerable 50% in those under anesthesia, compared to their awake counterparts.

“The other side to our study is that we have shown that brain clearance is highly efficient during the waking state,” Mr. Franks said. “In general, being awake, active and exercising may more efficiently clean the brain of toxins.”

The findings, published in the journal Nature Neuroscience, introduce a potential paradigm shift in our understanding of how the brain eliminates toxins, a process previously attributed to the glymphatic system’s function during sleep. The glymphatic system has been thought to be a critical mechanism for removing brain waste, with prior studies linking quality sleep to a lower risk of dementia by facilitating the clearance of toxic proteins.