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)
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)