A soft wearable near-infrared spectroscopy system for detecting brain water dynamics linked to glymphatic activity during sleep

Sleep is a critical physiological process essential for overall brain health. Recent research shows that the glymphatic system is a key player in facilitating the metabolic waste clearance. However, the continuous real-time monitoring of brain water dynamics during sleep remains substantially challenging. Here, we introduce a soft, wearable near-infrared spectroscopy (NIRS) system to detect brain water dynamics potentially linked to glymphatic activity. The device features an integration of multi-wavelength LEDs and photodetectors. The in vivo study with multiple human subjects captures the device's overnight sleep monitoring in a natural home environment, revealing continuous changes in brain water dynamics across different sleep stages. Our results support the link between sleep stage-dependent water dynamics and glymphatic activity. Spectral analysis identifies several physiological rhythms during sleep, including respiration, heart rate, and oscillations linked to slow-wave activity. These advancements significantly enhance the NIRS system's potential for a deeper understanding of brain health.