Characterizing the modern light environment and its influence on circadian rhythms
Dennis Khodasevich1, Susan Tsui2, Darwin Keung1
1Environmental Health Sciences, Mailman School of Public Health, Columbia University, New York, NY, USA.
Proceedings. Biological Sciences
|July 21, 2021
Summary
Modern humans experience less natural light exposure, disrupting circadian rhythms. This study reveals artificial light
Area of Science:
- Chronobiology
- Environmental Health
- Human Physiology
Background:
- Modern lifestyles involve extensive use of artificial light, altering natural light-dark cycles.
- Circadian disruption is implicated in various diseases, but population-level extent is unclear.
Purpose of the Study:
- To quantify light exposure and its impact on circadian phase timing in an urban population.
- To investigate the influence of artificial light on human circadian rhythms across seasons.
Main Methods:
- Measured individual light exposure and wrist temperature across four seasons in an urban setting.
- Compared individual light exposure to outdoor light sensors.
- Modeled the effect of morning and night light exposure on wrist temperature rhythm phase.
Main Results:
- Individuals had significantly lower daily light exposure than outdoor sensors year-round.
- Minimal seasonal variation in perceived photoperiod, except between winter and summer.
- Night-time light exposure delayed wrist temperature maximum, while morning light advanced it.
Conclusions:
- Humans minimize natural seasonal light variations, leading to reduced seasonal differences in light exposure.
- Artificial light exposure significantly influences circadian timing, with opposing effects from morning and night light.
- Circadian shifts and disruptions are likely common in the general population due to artificial light exposure.
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