Bundang Seoul National University Hospital Develops Real‑Time Measurement Technology for Sleep‑Based Brain ‘Cleaning’ to Prevent Dementia



A domestic research team has developed a technology that can monitor in real time whether brain waste products—including the toxic protein amyloid‑beta, which contributes to dementia—are being effectively cleared during sleep.

On July 23, Bundang Seoul National University Hospital announced that a joint team led by Professor Chang‑ho Yoon (Department of Neurology) and Professor Hyun‑min Bae (KAIST, Electrical & Electronic Engineering) has, for the first time worldwide, developed a non‑invasive, near‑infrared spectroscopy (NIRS)–based method to monitor the activity of the brain’s waste‑clearance system—the glymphatic system—during sleep.

When a person falls asleep, cerebrospinal fluid (CSF) surrounding the brain seeps deep into the tissue along perivascular spaces, washing away waste before being drained via the meningeal lymphatics or cervical lymph nodes. This inflow and subsequent outflow of CSF during sleep is called the glymphatic system, and one of its main targets is amyloid‑beta, whose accumulation over time is known to damage nerve cells and trigger Alzheimer’s disease.

The researchers used a wireless NIRS device sensitive to hydration changes to measure fluid flow inside the brain in real time. Attached to the forehead, this spectrometer emits near‑infrared light at wavelengths of 700–1,000 nm through the skull and analyzes the absorption of scattered light to calculate brain water content, oxygen saturation, and blood flow. By focusing on the water‑sensitive 925 nm wavelength and applying an algorithm to subtract the influence of cerebral blood plasma from total water measurements, they can isolate hydration changes directly linked to glymphatic activity.

In a validation study with 41 healthy adults, the team observed a significant increase in frontal‑lobe water content as participants transitioned from wakefulness into non‑rapid eye movement (NREM) sleep. The deeper the sleep stage, the more active the brain‑cleaning process—findings that align with glymphatic activation patterns seen in animal models. The largest rise in hydration occurred during the first deep‑sleep (NREM) cycle, suggesting that early sleep is a critical window for brain clearance and may inform future sleep‑therapy guidelines.

This study is the world’s first to develop a foundational technology that continuously measures brain water content throughout the entire sleep period in humans and quantitatively monitors glymphatic system activity in real time. The device was engineered as a wireless, non‑invasive system, making it highly promising for future extension into a home‑use wearable for brain‑health monitoring.

Professor Chang‑ho Yoon remarked, “This study is deeply meaningful in that we have developed the world’s first near‑infrared spectroscopy–based technology capable of quantitatively assessing glymphatic activity during sleep, thereby laying the scientific groundwork for elucidating the relationship between sleep and brain health. Going forward, it can be broadly applied not only to the early prediction and risk stratification of degenerative brain diseases such as dementia, but also to evaluating the effectiveness of sleep therapies and establishing personalized brain‑health management strategies.”