Entrainment of the Human Circadian Clock to the Natural Light-Dark Cycle

By Kenneth P. Wright Jr., A. Mchill, Brian R. Birks, Brandon Griffin, T. Rusterholz, Evan D. Chinoy. Current Biology, 2013

697 citations recorded by the source corpus.

Summary The electric light is one of the most important human inventions. Sleep and other daily rhythms in physiology and behavior however, evolved in the natural light-dark cycle[1] and electrical lighting is thought to have disrupted these rhythms. Yet how much the age of electrical lighting has altered the human circadian clock is unknown. Here we show that electrical lighting and the constructed environment is associated with reduced exposure to sunlight during the day, increased light exposure after sunset, and a delayed timing of the circadian clock as compared to a summer natural 14h40min:9h20min light-dark cycle camping. Furthermore, we find that after exposure to only natural light, the internal circadian clock synchronizes to solar time such that the beginning of the internal biological night occurs at sunset and the end of the internal biological night occurs before wake time just after sunrise. In addition, we find that later chronotypes show larger circadian advances when exposed to only natural light, making the timing of their internal clocks in relation to the light-dark cycle more similar to earlier chronotypes. These findings have important implications for understanding how modern light exposure patterns contribute to late sleep schedules and may disrupt sleep and circadian clocks.

Subfields: Endocrine and Autonomic Systems, Experimental and Cognitive Psychology, Global and Planetary Change

View Paper: https://www.semanticscholar.org/paper/2e43e4f393cc6811f619e1dc3adf69caec7442b5

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In Endocrine and Autonomic Systems

In Experimental and Cognitive Psychology

Citations in the corpus

When do you procrastinate? Sleep quality and social sleep lag jointly predict self-regulatory failure at work (2016, background): “This can be achieved by exposing oneself to more natural light during the day (e.g., being outdoors instead of staying indoors all day long), and by avoiding light during the night (Wright et al., 2013).”
Measuring Social Jetlag in Twitter Data (2016, background): “Many people now go to sleep much later than they would if they were exposed to natural sunlight during the day, and darkness free of light pollution in the evening (Wright et al. 2013).”
Chronotype and Social Jetlag: A (Self-) Critical Review (2019, background): “The internal inconsistency was inflated by a weakening zeitgeber strength [3]: shielding ourselves from daylight by living predominantly in buildings throughout the day and illuminating the night with artificial light have greatly weakened the zeitgeber’s strength and the artificial light in the eve”
The Circadian Clock and Human Health. (2016, background): “The impact of the light environment on human chronotype has been investigated by a study [42] documenting activity/rest cycles and melatonin onset in urban life compared to outdoor camping (no artificial light at night and bright, natural light during”