The circadian rhythm is a variation in physiology and behavior persistent with a cycle length close to 24 hours, and regular sun exposure and dark exposure are is necessary to keep the cycle intact. The circadian cycle in humans is approximately 24-hours in length and must be reset on a daily basis in order to remain in synchronization with the external environment. Sun exposure at the correct times of day is exceptionally important to human health, and when the cycle is disrupted by lack of light, such as that experienced by shift workers, or by those who live constantly indoors, it leads to a feeling of being “out of sync.” Disruption of the circadian rhythm may lead to increased breast-and/or-colorectal cancer risk in women,  and research has demonstrated that disruption of circadian rhythms may lead to a profound increase in the risk of heart disease, metabolic syndrome, lung cancer and other cancers. 
According to the Journal Sleep Health, morning daylight exposure helps to reset the circadian rhythm or properly maintain it, which leads to better sleep at night. The authors and researchers used a specialized device to measure the type of light that keeps the circadian rhythm of the human body properly set. By comparing workers in different buildings for sleep quality, they determined that those who received higher levels of morning light had considerably better sleep quality. They stated this conclusion: “The present study is the first to measure personal light exposures in office workers using a calibrated device that measures circadian-effective light and relate those light measures to mood, stress, and sleep. The study’s results underscore the importance of daytime light exposures for sleep health.” See also this link: http://sunlightinstitute.org/sleep-quality-is-improved-by-exposure-to-nature-and-sunlight/
Insomnia is a terrible problem in our modern life. To a great extent, that problem could be solved by arising early and taking advantage of an hour of morning sun exposure.
Safely enjoy your sun exposure, sleep tight and improve your health!
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