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Sleep Through The Ages

full moon on dark night sky

Studies suggest it may be more difficult to fall asleep when the moon is full. (Ulrich Peters, Flickr)

Without electricity and unnatural light, people would go to bed with sunset.

Before the Industrial Revolution, when work days started to run later, it was not unusual for sleep to be broken up into two parts throughout the night. Bimodal, or biphasic sleep refers to the concept that humans do not necessarily need to operate on 7 to 9 hours of continuous sleep.

Generally, these parts were broken up in two, four-hours chunks with about an hour of activity puncturing sleep. During this time, people would continue to rest or do simple tasks, such as chores or praying.

an illustration of two men and a young woman having a meal

Dickens’ Barnaby Rudge is his fifth published novel, set mostly during the Gordon Riots of 1780. It is one of many pieces of literature predating the Industrial Revolution that references a “first” and “second” sleep during the night. (Internet Archive Book Images, Flickr)

Cycles and Biphasic Sleep

According to historian A. Roger Ekirch and sleep researcher Siobhan Banks, some people naturally still wake up in the middle of the night, but experience anxiety because they believe they need to sleep continuously through the night.

But biphasic sleep can correspond healthily with our natural sleep patterns.

In one experiment, 15 male subjects were studied as they slept in circumstances lacking any unnatural light to imitate the conditions of prehistoric people. After three weeks of this, the subjects’ sleep became biphasic.

This suggests that biphasic sleep is a natural process. The 7 to 9 hours people operate on today may even disrupt natural circadian rhythms.


Some individuals even strive to operate on a sleep schedule with multiple phases because they believe it makes them more productive. A more mild form of biphasic sleep is an afternoon nap.

Shift sleep requires effective planning and ideal circumstances. It requires schedule regularity to enable a consistent bedtime. This ensures that you can wake up naturally and fall back to sleep easily.

A sleep cycle is sensitive and can be disrupted by hormonal changes that are caused by blue light emitted by electronic screens. This blue light disrupts melatonin, making it hard to operate on a consistent biphasic cycle.

a cell phone on a keyboard

Web surfing and texting may seem harmless. But blue light emitted by screens disrupts the production of melatonin, the hormone that regulates sleep cycles. (Linuxbear, Flickr)

If operating on a biphasic schedule, technology should be avoided as another way of regulating the circadian rhythm. A biphasic schedule relies on a consistency so you can fall asleep and wake up at the same times.

Sleep Culture

Different cultures’ attitudes toward sleep vary.

In the Middle Ages, it was seen as an inconvenience that interrupted work. Ancient Egyptians respected and revered sleep. They even had sleep temples devoted to healing.

Hit Snooze

Benefits of adequate sleep include better memory, longer lifespan, healthier weight, and better mental health.

Regardless of whether sleep is split into two phases or a continuous night time slumber, an average of eight hours is still necessary for most humans.

Sources And Further Reading:

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