WEDNESDAY, Jan. 27, 2021 (HealthDay News) -- Moonlight feels right, the '70s song insists -- and that old nugget might have been onto something.
Scientists have long known that conditions favorable for night-time "pre-sleep" -- sleep relatively early and wake relatively late -- can foster smart sleep, but studies failed to explain why exactly.
Now a new study suggests that darkness isn't simply a matter of "being differently stimulated than you are in the daytime." Rather, the natural selection of darkness based on the biology of animals gives way to darkness during darkness.
"Decades ago, many scientists thought that the body was circadian, but the body is arguably a special-purpose organ that is 'turned' to a hard-wired pattern of a biological maturation, so to speak," said HHMI researchers May King and Christine Johnson Statistics Banek-Adamson in a Dec. 15 Science Advances article. "Even experts who wouldn't ordinarily propose that the body's circadian rhythm plays a role in limiting sleep called for more precise experimental designs."
Previous experimental research has made it clear that changing lighting produces a natural pattern of periods of "pre-sleep" sleep and periods of wakefulness -- well-known themes in research from the 1950s on.
And having a night in which both sleep stages are conserved, sometimes only by around 10 minutes, has long been said to promote better sleep.
Elephants, for instance, can stay awake for several days and transit from morning to night without minimal or uncomfortable side effects. And especially heavily pregnant and nursing mother, they usually spend the majority of their time asleep during the regular daytime hours.
But is night-time darkness really a potent sleep aid?
KING and JOHNSON's study, from the Institute for Behavioral Medicine at Harvard University, focused on whether impaired sleep can be a side effect of light exposure in a broad range of animals.
"Overall, we found that intensely bright light, either on cloudy or sunny days, is not enough to shut down sleep," Khan explained. Instead, problems persist if sunlight is switched off before darkness begins.
A similar approach has been used in laboratory animals, where easily-controlled conditions can be used to determine whether light affects sleep in a controlled manner -- because as Khan pointed out, animals can be "made to exhibit almost any behaviors they desire by surprising them with small, unobtrusive changes to behavioral devices I test after adjusting the light setting."
Indeed, in the 2001 study, a set of genetically modified mice underwent a nine-hour light-dark transition, making sure the lighting they experienced was ideally timed
Scientists have long known that conditions favorable for night-time "pre-sleep" -- sleep relatively early and wake relatively late -- can foster smart sleep, but studies failed to explain why exactly.
Now a new study suggests that darkness isn't simply a matter of "being differently stimulated than you are in the daytime." Rather, the natural selection of darkness based on the biology of animals gives way to darkness during darkness.
"Decades ago, many scientists thought that the body was circadian, but the body is arguably a special-purpose organ that is 'turned' to a hard-wired pattern of a biological maturation, so to speak," said HHMI researchers May King and Christine Johnson Statistics Banek-Adamson in a Dec. 15 Science Advances article. "Even experts who wouldn't ordinarily propose that the body's circadian rhythm plays a role in limiting sleep called for more precise experimental designs."
Previous experimental research has made it clear that changing lighting produces a natural pattern of periods of "pre-sleep" sleep and periods of wakefulness -- well-known themes in research from the 1950s on.
And having a night in which both sleep stages are conserved, sometimes only by around 10 minutes, has long been said to promote better sleep.
Elephants, for instance, can stay awake for several days and transit from morning to night without minimal or uncomfortable side effects. And especially heavily pregnant and nursing mother, they usually spend the majority of their time asleep during the regular daytime hours.
But is night-time darkness really a potent sleep aid?
KING and JOHNSON's study, from the Institute for Behavioral Medicine at Harvard University, focused on whether impaired sleep can be a side effect of light exposure in a broad range of animals.
"Overall, we found that intensely bright light, either on cloudy or sunny days, is not enough to shut down sleep," Khan explained. Instead, problems persist if sunlight is switched off before darkness begins.
A similar approach has been used in laboratory animals, where easily-controlled conditions can be used to determine whether light affects sleep in a controlled manner -- because as Khan pointed out, animals can be "made to exhibit almost any behaviors they desire by surprising them with small, unobtrusive changes to behavioral devices I test after adjusting the light setting."
Indeed, in the 2001 study, a set of genetically modified mice underwent a nine-hour light-dark transition, making sure the lighting they experienced was ideally timed
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