Validation of a Multimodal Wearable Device for Assessing Environmental and Behavioral Risk Factors of Myopia in Children and Adolescents.

PURPOSE: To validate a wrist-worn multimodal wearable system for synchronised monitoring of multispectral light exposure, activity phenotypes and five-stage sleep architecture in children and adolescents in a structured 24-h pilot validation protocol. METHODS: A wrist-mounted multimodal wearable system was developed, integrating a 9-channel multispectral light sensor (350-1000 nm), a 9-axis inertial measurement unit (IMU) and a photoplethysmography (PPG) sensor for synchronised acquisition of environmental light, body movement and cardiovascular signals. Twelve healthy children and adolescents (mean age: 10.04 ± 3.26 years; range: 6-15 years) underwent a 24-h pilot validation protocol. Long short-term memory (LSTM) networks were developed for activity recognition and a Stacking ensemble framework combined with cost-sensitive learning was implemented for five-stage sleep classification, i.e., wake (W), non-rapid eye movement stage 1 (N1), non-rapid eye movement stage 2 (N2), non-rapid eye movement stage 3 (N3) and rapid eye movement (REM). RESULTS: Under the three lighting conditions tested, the device captured distinct spectral irradiance profiles: outdoor natural light (1.8 W m-2 nm-1; broad-spectrum 350-1000 nm), indoor natural light (0.30 W m-2 nm-1) and artificial illumination (0.07 W m-2 nm-1; peak at 545-600 nm). The LSTM-based model achieved 86.33% overall accuracy for five-activity classification, with 92.4% for writing and 91.5% for walking. The Stacking ensemble sleep classifier attained 83.41% overall accuracy; cost-sensitive learning improved N3 and REM detection by 15.8% and 8.9%, respectively. Incorporation of PPG signals enhanced activity recognition accuracy by 3.62%. CONCLUSIONS: This multimodal platform enabled objective, high-resolution quantification of paediatric light exposure, behaviour and sleep architecture in a structured pilot validation setting, supporting individualised assessment of modifiable myopia-related factors.