Doctor's Review: Medicine on the Move

January 27, 2022

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The long and short of bimodal sleep

Lying down for eight straight hours used to be a bad thing

Our not-so-distant ancestors had no trouble getting to sleep at night. In fact, they did it more than once. "Bimodal sleep," as it's called now, may have been their answer to not only sweet dreams, but to a deeper overall sense of peace. How did we sleep before we began to sleep the way most of us do today? What can we learn from sleeps past?

Sleep historian Roger Ekrich knew he was onto something when he started keeping track of references to "two sleeps" in old books, diaries, medical papers and hundreds of other documents, including the Bible. Sixteen years of research led him on a journey through countless mentions of "first sleep" and "second" or "morning" sleep. A character in Chaucer's Canterbury Tales sleeps "hire fyrste sleep & thanne a-wok." A 16th century French physician concludes that the working class produces more offspring due to their practice of waiting until after their "premier sommeil" to conceive. In Homer's Odyssey, book four, Proteus's daughter Eidothea tells Menelaus to seize her father "in his first sleep." And in Latin texts, there are multiple references to primo somno or concubine nocte. Ekrich published his findings in a 2009 book entitled At Day's Close: Night in Times Past.

First or "deep" or "dead" sleep, as it was sometimes called, often seems to have taken place shortly after sunset, or at least before 10 in the evening. After two to four hours of the night's deepest rest, people would wake up for an hour or two, then resume sleep for another stretch before rising with the light.

Ekrich was struck by the ordinariness of the mention of first and second sleeps, as though it were a practice so commonplace as to be truly unworthy of explanation. And while he suspected that sleeping twice in a single night might have been healthier than the unbroken eight-hour sleep that today is considered the epitome of sleep, what really impressed him was what people got up to in that deep dark hour of wakefulness between sleeps.

One thing was clear: the absolute darkness and silence of the hour made it a perfect time for prayer. In fact, further evidence of the naturalness of sleeping twice can be found in Islam, which strongly suggests that its devotees include a prayer, called the Tahajjud, between sleep in the final third of the night. Some Christian churches hold regular midnight masses and historically members of oppressed religions found the so-called witching hour the perfect time to gather and pray. Monks of all traditions have considered the time of absolute stillness as ideal for meditation.

Dream analysis, love-making and creative ruminations were also favourite activities during "the watch," another name given to midnight wakings. Thomas Jefferson, the third president of the United States, was in the habit of taking up books on moral philosophy before bed with the intention of waking after his first sleep to 'ruminate' over them. A century earlier, poet Francis Quarles (1592-1644) praised the hour between sleeps, saying, "Let the end of thy first sleep raise thee from thy repose: then hath thy body the best temper, then hath thy soul the least encumbrance; then no noise shall disturb thine ear; no object shall divert thine eye."

An odd handful of modern creatives have extolled the virtues of what is today considered an eccentric practice. Architect Frank Lloyd Wright woke at four, worked for several hours, and then resumed sleep. Psychologist B.F. Skinner kept paper and pen at his bedside for night wakefulness, and Nobel-Prize-winning Norwegian novelist Knut Hamsun regularly woke in the dead of night to write.

Loss of wathfullness

When the majority of us lost the practice of sleeping twice, we not only meddled with our circadian rhythms we lost our connection to the serenity of the watchful but somnolent state, an oceanic consciousness that honoured our right-brain capacities. Could the loss of this nighttime immersion in dreamy pontifications and meditative merging with the divine be at least partly responsible for the current proliferation of anxiety and mood disorders which often lead to sleeplessness?

Eye-opening studies of shut-eye made in the 90's support the concept of bimodal sleep as a natural human tendency, and also suggest that there's a hormonal component to the peace we feel in the middle of the night.

Thomas Wehr, now a scientist emeritus at the National Institute of Mental Health, has done some interesting work in photoperiodicity, or how exposure to light affects sleep. In the early 1990s, he placed 14 volunteers in total darkness for 14 hours a day every day for a month. After a period where they slept in the dark an average of 11 hours, the subjects settled into to a pattern of sleeping for an average of eight hours a night in two segments, separated by an hour or two of contemplative wakefulness. Wehr hypothesized that this was a return to a more primitive pattern of sleep.

Other studies have shown that during the period of wakefulness, the pituitary gland excretes high levels of prolactin, the hormone associated with the surreal hallucinatory pre-sleep state. Prolactin is also the hormone produced when nursing mothers lactate, as well as during orgasm.

So how exactly were we robbed of the pleasures of segmented sleep? The first demons to disrupt our ancient sleep patterns were artificial lighting and clocks. That old saying about burning the candle at both ends is evidence that as soon as people had the means to eat away at the night, they did. But time, or rather, the keeping track of it, was the more powerful enemy. Before mechanical clocks replaced sundials, the night was a mysterious realm which could not be subdivided into minutes and seconds. Clocks and personal time pieces went hand in hand with industrialization and quickly became the instruments which undid sleep as it has been practiced for millennium.

Clock-time introduced the concept of "wasting time" and what could be more wasteful than lying in the dark doing nothing with no explicable reason to do so? Tiredness and the need for sleep increasingly became a sign of moral lassitude. As the popularity of street lighting grew, the night retreated.

Paris was the first to light its streets, using wax candles in glass lanterns in 1667, followed closely by Lille, Amsterdam and eventually London. By the time the candles were replaced with gas, people had lost most of their associations of with night with thieves, fierce animals and witches.

As bedtimes grew later and later, references to "two sleeps" began to fade and to be seen as a bad thing. Parents were even encouraged to purge their children of any night-waking tendencies. An article in an 1829 British medical journal instructs parents that, "If no disease or accident there intervene, they will need no further repose than that obtained in their first sleep, which custom will have caused to terminate by itself just at the usual hour. And then, if they turn upon their ear to take a second nap, they will be taught to look upon it as an intemperance not at all redounding to their credit."

Sleepless disasters

What do the Exxon Valdez oil spill, the nuclear incidents at Chernobyl and Three Mile Island, and the explosion of the space shuttle Challenger have in common? They are all the casualties of sleep deprivation. In recent years, the whittling away of sleep has been blamed, in the literature, for everything from accelerated aging, obesity, heart attacks, cancer and neurodegenerative disease. The 24-hour garbage cycle takes a heavy toll on the environment.

So should we all revert to our primitive ways? One online group, the Polyphasic Society, encourages the establishment of broken sleep schedules and hosts forums on "sleep hygiene" and the exploration of personal sleep patterns. But some sleep experts express caution at the idea of reverting to bimodal sleep. Considering today's busy schedules, they fear people would grab the first sleep but skip the second, leaving many more exhausted than they already are. The current thinking is that it’s best to stick to the old stalwart -- seven-to-eight hours – a night, maintain regular bedtimes and pay off "sleep debts" as soon as possible.

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