Scientists at the University of Colorado, Boulder found that if you live by the sun’s schedule, you are more likely to go to bed one hour earlier, wake up one hour earlier, and be less tired, because your internal and external clock are in sync. The sun adjusts your internal clock to its natural state, undoing the influence of artificial light. The recent study is published in the current issue of the journal Current Biology.
The disconnect between the outside environment and sleep is one reason why even native Alaskans have problems sleeping in the almost endless days of the Arctic summers, and get depressed during the long nights of winters. The subjects in the Colorado study lived more normal lives.
The study looked at a small sample of eight adults, average age around 30, and followed them around the normal course of their lives for a week. Subjects spent the majority of their time indside while working, studying, and sleeping. Most of the light they encountered was artificial. Then, they sent the same people out camping.
Sleep and light were measured daily and the hormone melatonin every hour across 24 hours, once after the week of living at home, going to work, school, and then after a week of camping.
Melatonin is the “hormone of darkness,” said Namni Goel, a psychologist and sleep researcher at the University of Pennsylvania in Philadelphia. Scientists use the hormone to measure photoperiods, or the physiological response that organisms have to cycles of daylight and darkness.
After the week’s study indoors, the Colorado subjects went camping in the Rockies. Instead of artificial lighting, they had only sunshine during the day and campfires at night. Wright estimates the light from the sun was four times as intense as what they experienced indoors. The nature of the light also changed during the day. Think of the bright white light of midday and the golden glow that often precedes sunset. After their week of camping, researchers measured the subjects’ melatonin levels again.
The researchers found that the onset of melatonin shifted two hours earlier, and the subjects’ actual sleep shifted more than an hour earlier. Their bodies were recalibrating themselves, Wright explained.
When they woke in the morning in their normal lives, the melatonin and the external time were in conflict. They were waking up, but the melatonin in their bodies was telling them they should still be asleep. That might account for their still feeling sleepy, Wright said.
Full article: www.scientificamerican.com
