At first I dreaded having to investigate the history of sleep. Human slumber appeared impervious to time and place, stubbornly immune to the element of change animating most works of history. My own sleep was blissfully tranquil. No surprise, in my view, that historians, save for a few studies of dreams, had not explored a topic manifestly monotonous and uneventful. Samuel Johnson answered his own question when he wondered in 1753 why “so liberal and impartial a benefactor as Sleep should meet with so few historians.” But I had embarked on writing a book about nighttime in the centuries prior to the Industrial Revolution, and omitting sleep was unthinkable. “The brother of death exacteth a third part of our lives,” wrote Sir Thomas Browne. Death — traditionally the most common metaphor for sleep. Somehow I needed to fashion a chapter that would hold a reader’s interest, as well as my own.
So it was all the more welcome when I learned that human slumber has a history. Not only sleep but popular perceptions of its value have varied from one era or culture to the next. Before the modern age, Western households took extraordinary pains to ensure both the quality and the safety of their sleep, which promised to restore withered spirits as well as physical health. To fall asleep, according to an East Anglian saying, was to “forget the world.” Bug hunts, magical amulets, prayers, and potions were just a few of the precautions taken at bedtime — often in vain, according to diaries and medical texts. Threats to peaceful repose, both real and imaginary, lurked everywhere, from frigid temperatures and fleas to the Prince of Darkness, ruler of a shadow government at war with the kingdom of Christ. At no other time did families seem so vulnerable.
More than that, preindustrial sleep, I came to discover, was segmented. Unlike the seamless slumber we strive to achieve, sleep once commonly consisted of two major intervals, a “first sleep” and a “second sleep,” bridged after midnight by an hour or more of wakefulness in which people did practically everything imaginable. They rose to perform chores, tend to sick children, raid a neighbor’s apple orchard. Others, remaining abed, recited prayers and pondered dreams. The sixteenth-century French physician Laurent Joubert attributed the fecundity of manual laborers to early-morning intercourse “after the first sleep” when they “have more enjoyment” and “do it better.” To judge from textual references as early as Homer’s Odyssey, the prevailing mode of slumber for ages was biphasic. Virgil’s Aeneid, composed in the first century b.c., speaks of the “hour which terminates the first sleep, when the car of Night had as yet performed but half its course.”
There was scientific support for segmented sleep in a clinical study conducted by researchers at the National Institute of Mental Health in the early 1990s. More than a dozen male subjects, deprived of artificial light at night for several weeks, began sleeping in segments. Moreover, ethnographic evidence indicated that a variety of non-Western cultures, bereft of modern lighting, experienced first and second sleep — among them the Tiv of central Nigeria and the Surinamese Maroons. In short, far from being timeless, our form of slumber today is remarkably young, with a provenance dating back only two centuries, not to the primeval past.
Not until the late 1800s did segmented sleep arouse medical concern in the West. By then, sleep had become consolidated and compressed, a consequence both of the growing pervasiveness of artificial illumination (first gas, then electric), which reconfigured the human body’s circadian clock, and of a heightened emphasis on efficiency and productivity born of the Industrial Revolution. For mounting numbers of people on both sides of the Atlantic, sleep became a necessary evil best confined to a single interval. A go-getter, remarked one London writer, could steal “a march, so to speak, on the day and on one’s fellow human beings, who are enjoying that second sleep.” Parents were instructed to mold children into early risers while their habits remained unfixed. As early as 1829, an article in the Philadelphia-based Journal of Health cited the wisdom of “an experienced writer”:
If no disease or accident intervene, they will need no further repose than that obtained in their first sleep, which custom will have caused to terminate of itself, just at the usual hour, and then, if they turn upon the other ear to take a second nap, they will be taught to look upon it as an intemperance, not at all redounding to their credit.
Not that this transformation occurred overnight. The evolution of modern sleep was protracted and uneven, spanning the better part of the 1800s. By century’s end, however, the normality of seamless slumber was broadly accepted.
Following the publication of my research, first in the form of an academic article and then as a chapter in my book, the subject of sleep progressively intruded on my waking hours. What I had initially thought tangential to a study of nocturnal culture became instead a source of widespread interest. Newspaper reviews and radio appearances invariably became discussions of first and second sleep. I was invited to speak to medical gatherings (something I had not done since supervising a group of premeds years ago as they took the MCAT).
I also received emails from patients suffering from “middle of the night” insomnia. Most expressed relief when they learned that their wakefulness was not necessarily abnormal — indeed, viewed from the cosmic perch of history, their slumber appeared quite natural. In the view of David Neubauer, a specialist in sleep medicine at Johns Hopkins, consolidated sleep, as an artificial invention of modern life, may be inherently unstable. It also stands to reason that completing the transition from biphasic sleep, preeminent in all likelihood since time immemorial, would take longer than one or even two centuries.
A growing number of doctors who treat insomniacs believe that knowledge of segmented sleep can help patients fall back asleep by easing their anxiety. In replying to emails, more than once I felt obligated to point out — and to remind myself — that I was a historian, not a physician. Even so, I set about acquiring a better understanding of sleep and its discontents, both dyssomnias — encompassing insomnia and hypersomnia (excessive sleepiness during the day) — and parasomnias (abnormal behavior during sleep, from teeth grinding to sleepwalking).
As my immersion in sleep medicine deepened, I grew more cognizant of my own slumber, which began to take a turn for the worse. An odd tingling in my lower legs, which I had never much noticed, hindered my ability to sleep. When I mentioned this to my doctor, he responded, “Restless-legs syndrome,” a disorder typically characterized by an uncomfortable sensation of uncertain origin resulting in the need to move one’s legs. Several months passed, and I started to nod off occasionally in the midafternoon for an hour or more. The diagnosis: inadequate rest resulting from sleep apnea, wherein breathing becomes shallow or broken and the quality of nighttime sleep becomes poor. Neither of mine was a peculiar ailment, particularly for a middle-aged man who could stand to lose weight.
Two years after the publication of my book, I was invited to deliver a talk in Cambridge to a meeting of the British Sleep Society. (“That sounds like a lively bunch,” muttered the officer at Heathrow’s passport desk.) On the final evening of the conference, John Shneerson, a leading authority in sleep medicine, asked me to collaborate on a pair of articles on the history of sleep violence, including a discussion of REM sleep behavior disorder (RBD).
The most notable symptom of RBD is the repeated attempt to act out one’s dreams. In 1200 a.d., the author of the Questions de maître Laurent observed, “It happens that many men get up at night while asleep, take up weapons or staffs, or get on horseback.” “What,” he asked, “is the cause of this? What is the remedy?” Although most RBD cases do not result in violence against others, there is always a risk of minor (if only self-inflicted) injury. As late as the nineteenth century, the most effective remedy was to require adult sufferers to sleep alone, occasionally behind locked doors. A few tried tying themselves to their beds.
It was not long after I began studying these cases that I tackled my nightstand, which in my sleep I mistook for a football player. Despite my fresh interest in sleep violence, I shrugged off the episode. Only months later, after punching the headboard of my bed, imagining it to be a threat to my parents, did I comprehend the seriousness of my illness.
Fortunately, medication and, in some instances, therapy help inhibit RBD and other forms of sleep violence. I currently take a low dose of clonazepam (Klonopin), which is often recommended for restless-legs syndrome but has proved effective for both conditions. What’s more, since I lost some weight my sleep apnea has diminished. At least for now, my slumber remains uninterrupted — notwithstanding an occasional impulse to experience firsthand the sleep of our ancestors, if only on a trial basis.