Scientists at the University of Rochester Medicine have found that strengthening the body's natural daily rhythms to improve sleep may help the brain recover after a stroke. The work points to a possible new way to support brain waste clearance and improve recovery well after the initial injury. Published in the Journal of Clinical Investigation, the study showed that interventions designed to reinforce circadian rhythms improved recovery in mouse models of stroke.
These improvements were accompanied by stronger activity in the glymphatic system, the brain's waste-clearing network, along with lower levels of inflammatory molecules that can persist after a stroke. The findings build on more than a decade of research led by URochester Medicine neuroscientist Maiken Nedergaard, MD, DMSc. Her laboratory discovered the glymphatic system in 2012.
This system moves cerebrospinal fluid through the brain, helping remove waste products and other debris. Later studies found that glymphatic activity is especially strong during sleep and plays an important role in maintaining brain health. Neuroscientist Lauren Hablitz, PhD, later helped show that glymphatic activity is influenced not only by sleep, but also by circadian rhythms, the body's internal 24-hour clock.
In a landmark 2020 study, Hablitz, Nedergaard, and colleagues demonstrated that glymphatic function follows daily cycles even independently of sleep, establishing a direct link between circadian biology and the brain's waste-clearing system. "The discussion of stroke recovery really starts with the idea that stroke is not just a vascular event, but also a disorder of timing," said Hablitz, lead author of the new study. Scientists have long known that strokes tend to follow distinct time-of-day patterns.
They occur more often during the morning and are frequently more severe near the end of the sleep period. After a stroke, many patients also develop disrupted sleep-wake cycles. Those disturbances have been linked with worse recovery, depression, and reduced quality of life.
"That led us to ask a simple question," said Hablitz. "If timing is broken after a stroke, can we improve recovery by reinforcing the biological clock?" When the Brain's Cleanup System Slows Down In a healthy brain, the glymphatic system carries cerebrospinal fluid along blood vessels and through brain tissue. This process delivers nutrients while helping remove waste products and inflammatory signals.
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