Poor Sleep Patterns Can Harm Brain Function and Raise Dementia Risk

Good sleep isn’t just about feeling rested — it plays a critical role in keeping your brain healthy by clearing out harmful toxins while you sleep.

A new study has found that poor sleep can significantly impair the brain’s natural waste-removal system, potentially increasing the risk of dementia later in life.

Published in the journal Alzheimer’s & Dementia, the research analyzed MRI scans from nearly 40,000 adults in the UK Biobank. Scientists focused on the glymphatic system — the brain’s built-in cleaning mechanism.

Here’s how it works: During deep sleep, cerebrospinal fluid (CSF) flows through the glymphatic system, collecting metabolic waste and toxins from the brain and flushing them out. This process is essential for maintaining brain health.

Researchers from the University of Cambridge discovered that reduced or disrupted sleep negatively affects how efficiently the glymphatic system operates. When this waste-clearance system doesn’t work properly, harmful proteins such as amyloid and tau — which are strongly linked to Alzheimer’s disease — can build up in the brain.

“We already know that small vessel disease in the brain accelerates Alzheimer’s and other dementias,” said study author Hui Hong. “Now we have a likely explanation why. Disruption to the glymphatic system is likely to impair our ability to clear amyloid and tau from the brain.”

The study also found that impaired glymphatic function is associated with high blood pressure. According to Professor Hugh Markus from the University of Cambridge, at least a quarter of all dementia risk comes from modifiable factors such as high blood pressure and smoking.

“If these factors impair glymphatic function, then we have a clear opportunity to intervene,” Markus explained. “Treating high blood pressure and helping people quit smoking are practical, achievable ways to support better glymphatic function and potentially lower dementia risk.”

Dementia is an umbrella term for conditions that impair memory, thinking, and decision-making to the point where daily life is affected. It is not a normal part of aging, though age is a major risk factor. Alzheimer’s disease is the most common form of dementia.

The findings highlight the importance of maintaining healthy sleep patterns as a key strategy for protecting long-term brain health.