Health impact assessment of light and thermal environments: Field research in offices with wearable monitoring

Light and thermal environments are important determinants of human mood, alertness, sleep, and work performance in the built environment. Although these effects have been studied in controlled laboratory settings, there is still limited understanding of how daily exposures in real workplaces shape health and wellbeing. To address this gap, this study conducted a field investigation using wearable monitoring and repeated surveys to examine the dynamic relationship between environmental exposures and human responses. Eight office workers (aged 21-31) were observed for at least three working days. Each participant continuously wore a lightweight device that measured illuminance, melanopic equivalent daylight illuminance (m-EDI), and ambient temperature at 10-second intervals. Subjective data on mood, comfort, alertness, and self-rated work efficiency were collected via digital questionnaires, while physiological indicators including sleep-related indices from wrist-worn actigraphy were continuously recorded. The results showed that higher m-EDI levels in the half hour before survey completion were associated with more positive mood. Higher ambient temperatures were related to greater fatigue and lower work efficiency. Sleep duration tended to increase with higher morning light exposure and decrease with higher afternoon exposure. These findings suggest that light and thermal conditions have distinct and meaningful impacts on both psychological responses and sleep outcomes. This preliminary study demonstrates that combining wearable sensing with real-time subjective reporting can provide useful insights into how indoor environmental factors affect health and wellbeing. While limited by the small sample and short duration, the results highlight the value of field-based evidence for guiding healthier and more supportive workplace design, and point to the need for larger and longer studies in the future.