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.
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.
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.
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.
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:
- Bulger, Adam. "Our Ancestors Had Interesting Ways of Sleeping." Van Winkle's. November 11, 2016. Accessed May 24, 2018.
- Gordon, Amie. "Your Sleep Cycle Revealed." Psychology Today. July 26, 2013. Accessed May 24, 2018.
- "How Did People Sleep in the Middle Ages?" Medievalists.net. September 05, 2017. Accessed May 24, 2018.
- Jackson, Melinda, and Siobhan Banks. "Humans Used to Sleep in Two Shifts, And Maybe We Should Do It Again." ScienceAlert. June 2016. Accessed May 24, 2018.
- Marcin, Judith. "Biphasic Sleep: Schedule, Cycle, and Long-Term Effects." Healthline. September 8, 2017. Accessed May 24, 2018.
- "Natural Patterns of Sleep." Sleep and Memory | Need Sleep. December 18, 2007. Accessed May 24, 2018.
- Rimler, Rose. "Sleeping in Two Shifts: A History of Biphasic Sleep (Podcast with Transcript)." Sleep Review. May 15, 2017. Accessed May 24, 2018.
- Waugh, Rob. "World's 'oldest Beds' Found - and the Cavemen Who Slept on Them Even Used Mosquito Repellent." Daily Mail Online. December 08, 2011. Accessed May 24, 2018.
- Wehr, T. (1991). The Durations of Human Melatonin Secretion and Sleep Respond to Changes in Daylength. The Journal of Clinical Endocrinology & Metabolism,73(6). Retrieved June 6, 2018.