Individual-Level Exposure to Light at Night and Sleep Health: A Comparison between Real-Time Mobility-Based
Yuhan Cui1,2, Mei-Po Kwan1,2, Yang Liu1,2
1Department of Geography and Resource Management, The Chinese University of Hong Kong, Shatin, Hong Kong SAR 999077, China.
Environmental Science & Technology
|October 26, 2025
Summary
Light at night (LAN) disrupts sleep. This study found that how LAN is measured (indoor vs. wrist-worn devices) affects results, highlighting the need for accurate light exposure quantification in sleep research.
Area of Science:
- Chronobiology
- Sleep Science
- Environmental Health
Background:
- Light at night (LAN) is known to disrupt circadian rhythms and negatively impact sleep health.
- Previous observational studies show inconsistent findings regarding LAN exposure and sleep, potentially due to methodological differences in measurement techniques.
Purpose of the Study:
- To investigate and compare indoor residence-based measurements (IRBM) and real-time mobility-based measurements (RMBM) of LAN exposure.
- To examine the associations between these different LAN measurement methods and objective/subjective sleep health outcomes.
- To explore sex as a potential moderator in the relationship between LAN exposure and sleep health.
Main Methods:
- Data from 484 adults (aged 18-65) over 1,748 nights in Hong Kong.
- Objective sleep data via actigraphy and subjective data via sleep diaries.
- LAN exposure quantified using a portable light meter (IRBM) and a wrist-worn actigraph luxmeter (RMBM).
- Generalized linear mixed models were used, adjusting for numerous covariates.
Main Results:
- Significant differences were observed between IRBM and RMBM, with inconsistent associations initially.
- After covariate adjustment for LAN across astronomical night, discrepancies between IRBM and RMBM were attenuated.
- Both methods showed negative associations between LAN and objective sleep duration and efficiency.
- No significant effects were found on subjective sleep quality or sex moderation.
- RMBM showed instrumental error for LAN across biological night, leading to divergent associations.
Conclusions:
- Methodological choices in quantifying LAN exposure (IRBM vs. RMBM) and the chosen analysis window (astronomical vs. biological night) explain inconsistencies in prior research.
- Accurate quantification of light exposure is crucial for reliable sleep health studies.
- Future research should carefully consider and standardize LAN measurement techniques and analysis periods.
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