We tend to sleep late, well after dusk and in one long chunk. If we wake up in the middle of the night, we return to bed and hope we fall asleep again pretty quickly to avoid feeling wrecked in the morning. However, with a natural circadian rhythm and in the absence of artificial light, sleep researchers suggest that it’s likely that we would not sleep in one long 7-8 hour block.
Prior to modern electrical sources of light, people used to divide their sleep time into two segments, separated by several hours of night-walking. Such sleep pattern is called segmented sleep.
Roger Ekirch, a Professor of History at Virginia Tech, conducted a 16-year research covering hundreds of historical documents from ancient to modern times and across cultures. He identified countless references to "first" and "second" sleeps. It seems it was the normal daily cycle of sleeping and waking.
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"By turning night into day, modern technology has obstructed our oldest avenue to the human psyche, making us, to invoke the words of the 17th-century English playwright Thomas Middleton, “disannulled of our first sleep, and cheated of our dreams and fantasies”. - Ekirch quoting Middleton [1]
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That space between first and second sleep was quiet-wakefulness. A meditative silent space for prayer, reflecting on dreams, creative activities including writing (keep a pen and paper by your bedside for this purpose - you don’t want an excuse to pick up your phone), family bonding or sex, before returning to sleep and awakening once more with the sunrise or scheduled songs of the native fauna.
In order to prove that segmented sleep returns in the absence of artificial light, psychiatrist Thomas Wehr had conducted an experiment, where subjects had access to light for 10 hours per day instead of the current norm of the artificial light extended period of 16 hours. As a result:
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"Sleep episodes expanded and usually divided into two symmetrical bouts, several hours in duration, with a one- to three-hour waking interval between them" - Thomas Wehr [2]
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According to the research, light not only enables us to see fine detail, colour and motion, but also exerts non-visual effects on circadian rhythms, sleep and mood. Light at the wrong time may disrupt circadian rhythms and sleep. [3]
Learn more about the effect of artificial light on sleep quality.
Our ancestors would go to sleep a couple of hours after dusk and wake up in the middle of the night in a state involving high levels of prolactin, a hormone commonly associated with feelings of peacefulness, relaxation and dreamlike hallucinations we may experience as we fall asleep.
| "Blissfully zonked out by prolactin, our night brains allow ideas to emerge and intertwine as they might in a dream”- Karen Emslie, Scottish writer and essayist [1] |
Prolactin levels increase to their high night-time values during the first 30 minutes of darkness, long before sleep begins. But note that if the hours of quiet-wakefulness are disturbed by conversation, then prolactin levels do no rise.
The case for segmented sleep is that in the absence of artificial light, it is our natural way to sleep soon after dusk, wake at some time in the wee hours of the morning in a state of quiet-wakefulness, before returning to sleep and rising at dawn.
With new information, we can reassess the costs and benefits of an early vs later bedtime and see what better serves our goals. Waking up in the middle of the night may in fact, not be an insomnia disorder. Rather, it is completely normal and we’ve all simply been victims of technology, starting with the invention of the light bulb.
References:
[1] - https://aeon.co/essays/why-broken-sleep-is-a-golden-time-for-creativity
[2] - https://pubmed.ncbi.nlm.nih.gov/10607034/
[3] - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6751071/
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