Cross-validation of wearable light loggers across electric and natural light conditions: focus on illuminance, melanopic EDI, and CCT
- 1Healthy Living Spaces lab, Institute for Occupational, Social and Environmental Medicine, Medical Faculty, RWTH Aachen University, Aachen, Germany
Abstract
Wearable light loggers are increasingly used to assess light exposure in everyday environments in studies of circadian physiology and sleep, yet their accuracy under diverse lighting conditions remains insufficiently understood. This study evaluated three commonly used wearable light loggers (ActLumus, Lido and OcuWEAR) by comparing measurements of photopic illuminance, melanopic equivalent daylight illuminance (m-EDI), and correlated colour temperature (CCT) against a reference spectroradiometer under controlled laboratory conditions and in the field. Measurements were conducted across fluorescent, incandescent, and multiple LED sources, as well as under dynamic daylight exposure. Device performance depended strongly on both light source characteristics and metric type. Illuminance exhibited lower variability, whereas m-EDI and CCT showed substantial device- and condition-specific biases, particularly under spectrally atypical illumination conditions. These differences were consistent with spectral mismatch effects arising from standard photometric calibration practices. Importantly, the impact of measurement bias varied by exposure context: under dim light conditions, small absolute deviations led to substantial misclassification relative to currently recommended thresholds, whereas brighter electric light and daylight conditions were more robust. These findings highlight that device- and context-dependent biases can influence the interpretation of light exposure in circadian and sleep research, underscoring the need for careful device selection and data interpretation.
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BibTeX
@misc{pilehchiha2026crossvalidation,
title = {{Cross-validation of wearable light loggers across electric and natural light conditions: focus on illuminance, melanopic EDI, and CCT}},
author = {P. Pilehchi-Ha and O. Stefani and M. Schweiker and Y. de Kort and K. Smolders and J.-F. Harmsen},
howpublished = {medRxiv},
year = {2026},
month = oct,
doi = {10.64898/2026.10.06.26364836},
url = {https://www.medrxiv.org/content/10.64898/2026.10.06.26364836v1},
note = {CC BY-NC-ND},
}
RIS
TY - UNPB
TI - Cross-validation of wearable light loggers across electric and natural light conditions: focus on illuminance, melanopic EDI, and CCT
AU - P. Pilehchi-Ha
AU - O. Stefani
AU - M. Schweiker
AU - Y. de Kort
AU - K. Smolders
AU - J.-F. Harmsen
PY - 2026
DA - 2026/10/06
PB - medRxiv
DO - 10.64898/2026.10.06.26364836
UR - https://www.medrxiv.org/content/10.64898/2026.10.06.26364836v1
AB - Wearable light loggers are increasingly used to assess light exposure in everyday environments in studies of circadian physiology and sleep, yet their accuracy under diverse lighting conditions remains insufficiently understood. This study evaluated three commonly used wearable light loggers (ActLumus, Lido and OcuWEAR) by comparing measurements of photopic illuminance, melanopic equivalent daylight illuminance (m-EDI), and correlated colour temperature (CCT) against a reference spectroradiometer under controlled laboratory conditions and in the field. Measurements were conducted across fluorescent, incandescent, and multiple LED sources, as well as under dynamic daylight exposure. Device performance depended strongly on both light source characteristics and metric type. Illuminance exhibited lower variability, whereas m-EDI and CCT showed substantial device- and condition-specific biases, particularly under spectrally atypical illumination conditions. These differences were consistent with spectral mismatch effects arising from standard photometric calibration practices. Importantly, the impact of measurement bias varied by exposure context: under dim light conditions, small absolute deviations led to substantial misclassification relative to currently recommended thresholds, whereas brighter electric light and daylight conditions were more robust. These findings highlight that device- and context-dependent biases can influence the interpretation of light exposure in circadian and sleep research, underscoring the need for careful device selection and data interpretation.
ER -