We know by now the importance of sleep for the brain, body, and overall health. Sleep research has found that it’s best to sleep seven to nine hours a day. Still, many people suffer from sleep disorders, finding it difficult to fall asleep and sometimes even harder to stay asleep. Segmented sleep is one of these disorders.
One cause of sleep disruption is sleep apnea, when irregular breathing disturbs restful sleep. This can leave you feeling tired and groggy. Long term, sleep apnea can lead to memory loss and cognitive decline because the brain works while you sleep to cleanse itself. Without ample deep sleep, toxins build up and affect brain function.
Waking up in the Middle of the Night
Even if you don’t have sleep apnea, you may find you regularly wake up in the middle of the night. As it turns out, that’s normal! Up until the last century, segmented sleep was common. Historically, it seems, humans naturally tend to sleep in two parts each night, separated by a couple of hours of wakefulness.
Historian Robert Ekirch studied the sleep patterns of different cultures and documented his findings in his book At Day’s Close: Night in Times Past. A piece of his research was published in The American Historical Review in 2001.
“Sleep has remained among the most neglected topics primarily because the relative tranquility of modern slumber has dulled our perceptions of its past importance…Did most, in an era before sleeping pills, body pillows, and earplugs, enjoy the reasonable expectation of undisturbed rest? …notwithstanding idyllic stereotypes of repose in simpler times, early modern slumber remained highly vulnerable to intermittent disruption, much more so, in all likelihood, than does sleep today.” (1)
Segmented Sleep
Ekirch found over five hundred references to segmented sleep documented from as early as ancient Greece. Perhaps most relevant to us, he discovered that before the nineteenth century Industrial Revolution, most Western Europeans slept in two intervals, called “first” or “dead sleep” and “second” or “morning sleep”. The intervals lasted about the same period of time, the first ending around midnight. Other cultures engaged in this pattern of sleep and continue to this day. The time in between was spent in quiet prayer or meditation, socializing, reading and writing, or intimacy.
“Thus the basic puzzle remains—how to explain this curious anomaly or, in truth, the more genuine mystery of consolidated sleep that we experience today. For there is every reason to believe that segmented sleep, such as many wild animals still exhibit, had long been the natural pattern of our slumber before the modern age.” (Ibid.)
Indeed, modern science has delved into solving the puzzle. When deprived of artificial lighting for a period of several weeks, Thomas Wehr studied subjects in 1992 that naturally fell into a sleep cycle involving two intervals with a one- to two-hour break between. The length of time for sleep hormone secretion expanded, affecting the circadian rhythm (“body clock”): hormone levels increased before the first and second sleep period and decreased between the two. (2)
Our Natural Pattern
When it comes to sleep disruption, there is a complex physiology at work.
Russell Foster is a neuroscientist at Oxford University who has published many works on sleep patterns and their physical and mental effects. In an interview with the BBC, Dr. Foster explains that the rhythm of sleep is partially determined by the natural cycle of night and day as light is perceived by the eyes.
That’s not the whole story, however. Some people’s body clocks are different, i.e., “night owls”. For these people, night is a more productive time. Melatonin (one of the hormones that influence sleep) is regulated by the body clock. In most people, melatonin peaks between 4:00 and 6:00 a.m. but in some it’s ten to twelve hours later. Listening to your own body clock is very important for your health, he concludes.
Thomas Wehr agrees:
“Further research will be necessary to determine whether, and to what extent, darkness per se or factors associated with the dark condition were responsible for the differences that we observed in the subjects’ sleep.” (3)
Benefits of Segmented Sleep
Dr. Foster notes, “Many people wake up at night and panic. I tell them that what they are experiencing is a throwback to the bi-modal sleep pattern.” (4)
In a 2008 study, he states:
“The alarm clock can drive human activity rhythms but has little direct effect on our endogenous 24 hour physiology. In many situations, our biology and our society appear to be in serious opposition, and the damaging consequences to our health under these circumstances are increasingly recognised.” (5)
Behavioral Sleep Medicine Specialist Dr. Gregg Jacobs is an expert in naturally treating insomnia. (6)
He explains: “For most of evolution we slept a certain way. Waking up during the night is part of normal human physiology.” (7)
With segmented sleep, a surge of prolactin occurs during the period of wakefulness.
“There is evidence that the prolactin hormone surge associated with regular and stable night sleep segmentation can lead to improved sleep architecture, increasing restorative SWS [slow-wave sleep] in the first sleep, and increasing REM [rapid eye movement] in the second sleep.” (8)
That’s not to say you should set your alarm clock for 2:00 a.m. The point for consideration is that if you normally go to sleep for two to four hours, wake up for a while, and then fall back to sleep there’s no cause for alarm. If you wake for the day feeling refreshed, it’s your body following a natural rhythm.
If not, go to bed an hour or two earlier and use the time of wakefulness between sleep in a productive, reflective, but not-too-active way that would prevent you from falling back to sleep. Listening to your body is crucial for getting enough sleep that’s appropriate for you.
For more information on segmented sleep, check out the video below and the Polyphasic Society’s site here.
Readjusting Your Sleep
If segmented sleep is leaving you feeling drained and tired, here’s how to reset your sleeping pattern for good.
1. Stick to a Schedule
The best way to get a restful sleep is to follow the same sleep schedule every day. Unplug your electronics an hour before bedtime and give yourself an hour or so to go through your bedtime routine and relax before falling asleep.
2. Exercise
Exercising in t