Individual, behavioural, and environmental determinants of personal light exposure in daily life: A multi-country wearable and experience-sampling study

Zauner, J.; Didikoglu, A.; Aerts, S.; Agbeshie, G. K.; Akuffo, K. O.; Akgun, S. G.; Aydin, S. N.; Baeza Moyano, D.; Boesten, D.; Bolte, J. F. B.; Broszio, K.; Cantarero Garcia, G.; Gonzalez Lezcano, R. A.; Guidolin, C.; Hilden, S.; Hogervorst, N.; Jansen, A.; Kayar, Z.; Kallberg, S.; Lee, S.; Melero Tur, S.; Nilsson Tengelin, M.; Perez Gutierrez, M. C.; Sancho-Salas, A.; Stefani, O.; Svensson, I.; von-Breymann, H.; Spitschan, M.

doi:10.64898/2026.06.04.730226

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bioRxiv · 10.64898/2026.06.04.730226

Individual, behavioural, and environmental determinants of personal light exposure in daily life: A multi-country wearable and experience-sampling study

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Abstract

Light supports circadian regulation and is associated with non-communicable diseases, yet ocular exposure patterns remain poorly understood. We recruited 191 adults across nine sites in seven countries, combining diaries and contextual reports with near-eye (141 participants; 816 participant-days) and complementary chest-level measurements (154 participants; 902 participant-days). In near-eye analyses, only 24.0% of recorded daytime minutes met the recommendation of at least 250 lx melanopic equivalent daylight illuminance; 63.3% of pre-sleep and 87.7% of bedside sleep-environment minutes met their respective limits. Variation among people and days within sites exceeded that among sites (ratio 1.99; 95%-CI, 1.29-4.77). In hourly models, light source and setting contributed the largest shares of fitted variation after time of day. Site-average outdoor exposure was 9.35 times that while awake at home (95%-CI, 6.95-12.59; 714.2 versus 76.4 lx). This baseline identifies a daytime exposure gap and supports testing interventions in everyday settings to improve light exposure and health.

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Zauner, J., Didikoglu, A., Aerts, S., Agbeshie, G. K., Akuffo, K. O., Akgun, S. G., Aydin, S. N., Baeza Moyano, D., Boesten, D., Bolte, J. F. B., Broszio, K., Cantarero Garcia, G., Gonzalez Lezcano, R. A., Guidolin, C., Hilden, S., Hogervorst, N., Jansen, A., Kayar, Z., Kallberg, S., Lee, S., Melero Tur, S., Nilsson Tengelin, M., Perez Gutierrez, M. C., Sancho-Salas, A., Stefani, O., Svensson, I., von-Breymann, H., Spitschan, M.. 2026-06-09. Individual, behavioural, and environmental determinants of personal light exposure in daily life: A multi-country wearable and experience-sampling study. https://doi.org/10.64898/2026.06.04.730226

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