RSSNatural cycles reset your biological clock

Posted on Mon, 27 Feb 17

Natural cycles reset your biological clock

Late sleep timing and a disrupted biological clock is associated with several health issues and the cause is a lack of natural light dark cycles in modern environments, according to some remarkable new research. 

Disruption of circadian rhythm, the natural timing of your biological clock, has been recently linked to a wide range health problems from low energy and mood, to risk for certain cancers, heart disease and obesity. 

To investigate the effects of natural light-dark cycles a research team conducted a series of experiments which involved measuring biological rhythms, sleep and camping for a week in winter (9 hours 20 minutes light, 14 hours 40 minutes dark) or over a weekend in summer (14 hours 39 minutes light, 9 hours 21 minutes dark). 

After camping in the natural winter light-dark cycle average melatonin onset occurred 2.6 hours earlier, sleep start time 2.5 hours earlier and slept 2.3 hours longer when compared to the modern electrical lighting environment. 

And after the weekend summer camping melatonin onset occurred 1.4 hours earlier compared to 0.98 hours later with modern electrical lighting environment. This suggests that camping prevents a typical weekend circadian and sleep delay due to staying up later on weekdays, and thus higher exposure to electrical light at night. 

“…our findings demonstrate that the human melatonin rhythm adapts to short summer and long winter nights when living in a natural light-dark cycle—something that has been assumed but never demonstrated with respect to the ‘‘natural light-dark cycle,” commented the researchers involved. 

“We further show that living in the modern electrical lighting environment reduces seasonal circadian responsiveness by delaying the beginning of the biological night in both winter and summer.”


Stothard ER, et al. Circadian Entrainment to the Natural Light-Dark Cycle across Seasons and the Weekend. Curr Biol. 2017 Feb  2. pii: S0960-9822(16)31522-6.

Tags: Sleep Debt, Light At Night, Electrical Lighting, Sleep, Melatonin

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