Broken Sleep May Be Natural Sleep

Once again your patient, an accountant and tax specialist, is complaining about his sleep. More nights than not he awakens at about 2 am. An hour goes by, sometimes 2, before he returns to sleep. You've prescribed 4 different hypnotics. Each gave the same unsatisfactory result. For 2 weeks, your patient got the 8 hours of uninterrupted sleep he-and you-seek, but then the old pattern returned. Following your instructions, he avoids caffeine, doesn't exercise after 6 pm, and confines his activities in bed to sleep, but to no avail. You refer him to a sleep laboratory, and the results there are entirely consistent with what he's been telling you. In the sleep lab he falls asleep at 11 pm, awakens at 2:30 am, returns to sleep at 4 am, and awakens for good at 7:30 am. He does not have sleep apnea, restless legs syndrome, or depression.

Your patient seems more concerned as the years go on. You've suggested to him that when he wakes up, he should get out of bed and read until he gets sleepy. But he spends his awake time worrying about why he can't sleep and how his interrupted sleep will affect his work. The length of his time awake appears to be increasing. He insists that his daytime concentration isn't as good as it once was.

At a drug company-sponsored dinner, between the veal marsala and chocolate mousse, you learn that interrupted sleep is among the most common sleep problems and that a new hypnotic promises to be better than previous ones at providing "continuous sleep-consolidated sleep," as the speaker calls it. To her credit, the drug company-sponsored speaker does not shy away from the fact that the new hypnotic works by enhancing γ-aminobutyric acid transmission, just like the older ones.

Do you subject your patient to yet another drug trial, this time with a more expensive, albeit not very different, agent? Given your patient's misery about his sleep problem and the fact that you've exhausted the available options, such a course is not unreasonable. Yet a recent discovery, not from a drug company laboratory or a university research program but from a historian, suggests that there may be another, very different, way to relieve your patient's problem.

Sleep in times past
In the course of gathering information for his book about night in preindustrial times (At Day's Close: Night in Times Past), A. Roger Ekirch, professor of history at Virginia Polytechnic Institute, uncovered the fact that before artificial illumination was widely used, people typically slept in 2 bouts, which they called first sleep and second sleep.¹ In those times, sleep was more closely tied to sunset and sunrise than it is now. Within an hour or so after sunset, people retired to bed, slept for about 4 hours, and then woke up. They remained awake for a couple of hours and then returned to sleep at about 2 am for another 4 hours or so.

Written records from before the first century onward indicate that the period between first and second sleep afforded a chance for quiet contemplation, but people also got out of bed during this interval and did household chores or visited with family and friends. Although diaries, court documents, and literature of the time indicate that this sleep pattern was widely known and acknowledged, until Ekirch's work this bit of history had been lost to the current era. This pattern of sleep is no longer the norm in developed countries, where artificial light extends the day, but anthropologists have observed a similar pattern of segmented sleep in some contemporary African tribes.¹ Ekirch notes that the Tiv people of central Nigeria even use the same terms-first sleep and second sleep-used by the Europeans of times past.

Segmented sleep may be the natural pattern
Several lines of evidence suggest that this archaic sleep pattern may, in fact, be the natural sleep pattern-the one most in tune with our inherent circadian rhythms and the natural environment. In the early 1990s, Thomas A. Wehr, MD, then a sleep researcher at the NIMH, and his colleagues reported that when 8 healthy men had their light/dark schedules shifted from their customary 16 hours of light, 8 hours of dark to one in which they were exposed to natural and artificial light for 10 hours each day and confined to a dark room for 14 hours each night (durations of light and dark similar to the natural durations of day and night in winter) a sleep pattern similar to that of the preindustrial era developed.^2,3 They slept in 2 bouts of about 4 hours each separated by 1 to 3 hours of quiet wakefulness. Subjects usually woke from their first bout of sleep during a period of rapid eye movement (REM) sleep, when dreaming is most likely. The second bout of sleep was usually lighter than the first, with less stage-4 (deep) and more REM sleep.⁴ Thus, when freed from the time constraints on night imposed by modern work schedules and artificial illumination, subjects reverted to the segmented sleep of earlier times.

Also suggesting that interrupted or segmented sleep comes to us naturally, many animals that are active during the day-including chimpanzees, chipmunks, and giraffes-sleep at night in 2 distinct bouts separated by several hours.^4-6 In fact, Wehr points out, modern humans may be unique among animals in the extent to which their sleep is consolidated.

Wehr, now a Scientist Emeritus at the NIMH, thinks that our current sleep pattern, in which we fall asleep rapidly and expect to sleep (and often do) for an uninterrupted 7 or 8 hours, may be an artifact of both chronic sleep deprivation and artificial light. When the subjects of his experiments shifted from the 16-hour "days" and 8-hour "nights" customary for them (and for everyone else in developed countries) and which depend on artificial light, to the "natural winter" conditions of his experiment, they slept at first for 11 hours and then started sleeping for an average of 8.9 hours, compared with 7.2 hours under ordinary conditions.³

These and other data⁷ suggest that our current schedules do not allow us the sleep that we require. Wehr also observed that when given 14 hours of darkness, it took subjects at bed rest about 2 hours to fall asleep, compared with the 15 minutes under usual conditions.⁴ He speculates that under usu- al conditions, we may fall asleep so quickly because we are chronically sleep-deprived. Natural sleep, Wehr suggests, particularly during relatively long periods of darkness, is characterized by a long sleep latency and "interspersed with periods of wakefulness."⁴

The discoveries of Ekirch and Wehr raise the possibility that segmented sleep is "normal" and as such they hold significant implications for both the understanding of sleep and the treatment of insomnia. But sleep specialists are, for the most part, unaware of these findings and have not yet incorporated them in clinical practice. Part of the reason lies with the fact that these discoveries have not been widely disseminated. Ekirch's book received a good number of deservedly positive reviews, but it is, after all, history and is not at the top of most reading lists. While Wehr's sleep research is well known to sleep specialists, the thrust of his work has been on uncovering the mechanisms governing sleep. His discovery of segmented sleep was an unexpected, incidental finding from a study examining the influence of photoperiod on sleep and melatonin.²

Challenging current thought
Also working against the clinical application of these findings is the extent to which they fly in the face of current thinking. The general public seems to regard 7 to 8 hours of unbroken sleep as our birthright; anything less means that something is awry. Sleep specialists share this assumption. Sleep researcher J. Todd Arnedt, PhD, clinical assistant professor of psychiatry and neurology at the University of Michigan, acknowledges that the conventional approach to patients who cannot maintain sleep, and the one he uses, is to attempt to consolidate their sleep. He didn't know about the 2 bouts of sleep discovered by Ekirch and Wehr but, in light of that phenomenon, thinks that the conventional approach might not be the best one. He points out that how patients perceive their sleep determines to some extent how in fact they do sleep. He tries to get his patients with insomnia to "stop seeing their sleep as problematic." When they can do that, whatever sleep loss they encounter becomes more tolerable. If patients perceived interrupted sleep as normal, he points out, they might experience less distress when they awaken at night and fall back to sleep more easily.

Wehr agrees. He writes: "When modern humans find that their sleep is . . . interrupted by periods of wakefulness . . . they regard it as being disordered. . . . [A]n alternative explanation could be that a natural pattern of human sleep is breaking through into an artificial world in which it seems unfamiliar and unwelcome."

"Waking up after a couple of hours may not be insomnia," he says. "It may be normal sleep."⁴

Did the interval between bouts of sleep, common in earlier times, provide something of value or did our ancestors merely tolerate it? To be sure, this period offered our forebears an opportunity for uninterrupted sex, for quiet study, and for household chores.

Ekirch believes that the period of quiet wakefulness also offered a unique opportunity to contemplate dreams. People often awoke from a dreaming state and so were particularly likely to remember their dreams, and thus to gain access to an otherwise unavailable part of mental life. He believes that we may have lost something in our move to consolidated sleep.

Mary Carskadon, PhD, a sleep researcher at Brown University in Rhode Island, did not know of Ekirch's historical findings but did know of the segmented sleep pattern discovered by Wehr and of the fact that some animals take "2 sleeps." Considering these observations, she speculates that "maybe the brain can't keep you asleep for prolonged periods," and she wonders whether the archaic sleep pattern had some functional purpose. Like Ekirch, Carskadon believes that the change in sleep pattern "highlights something humanity might have lost in the hurly-burly times we live in today."

Much as we might envy the more relaxed sleep pattern of our forebears, we are unlikely to revert to it. As Carskadon points out, "It's hard to adapt to 2 bouts of sleep when you have to be at work at 8 am." She does feel, though, that it would benefit patients with interrupted sleep to tell them that such a sleep pattern may be natural.

The accountant troubled by broken sleep could well benefit from learning that the sleep pattern he finds so distressing may be more natural than the solid sleep he desires. And he should be told that in his nocturnal wakefulness he's far from alone. He's in the company not only of giraffes and chipmunks but also of his ancestors and many of his contemporaries. If the usual measures don't suffice to give him the solid sleep he wants, tell him to savor the period before he returns to sleep. It's a time to meditate, have sex, think about dreams. Or, as Wehr says, he can "just lie there and go back to sleep."

References:

References1. Ekirch AR. At Day's Close: Night in Times Past. NewYork: WW Norton; 2005.
2. Wehr TA. In short photoperiods, human sleep is biphasic.J Sleep Res.1992;1:103-107.
3. Barbato G, Barker C, Bender C, et al. Extended sleep inhumans in 14 hour nights (LD 10:14): relationship betweenREM density and spontaneous awakening. ElectroencephalogrClin Neurophysiol. 1994;90:291-297.
4. Wehr TA. Regulation of sleep and circadian rhythms.In: Turek FW, Zee PC, eds. Regulation of Sleep and CircadianRhythms. New York: Marcel Dekker; 1999.
5. Dijk DJ, Daan S. Sleep EEG spectral analysis in a diurnalrodent: Eutamias sibiricus. J Comp Physiol [A].1989;165:205-215.
6. Tobler I, Schwierin B. Behavioural sleep in the giraffe(Giraffa camelopardalis) in a zoological garden. J SleepRes. 1996;5:21-32.
7. Webb WB,Agnew HW Jr. Are we chronically sleep deprived? Bull Psychonomic Soc. 1975;6:47-48.