Tuesday, October 8, 2013
It's Normal to Sleep Like an Aardvark
Lately I’ve been sleeping sort of fitfully. I usually fall asleep fairly quickly, but then I wake up around 3 a.m. I can’t believe how wide awake I am; I can lay there for an hour or more before I start feeling drowsy again. I was going to ask the doctor if I’m suffering from a sleep disorder. However, then I ran across some sleep research by a psychiatrist named Thomas Wehr. In a month-long experiment Wehr kept individuals in a completely dark room for 14 hours a day (the length of a midwinter night in the Great White North). Instead of sleeping for the 8-hour stretch that we’re accustomed to thinking of as normal, individuals’ sleep patterns changed dramatically by the end of the month. Typically they lay quietly in bed for an hour or two. Then they fell asleep for a three to five hour period. They then woke up for an hour or two. And finally they went back to sleep for another three to five-hour segment. Thus, their sleep pattern was bimodal. Instead of a single uninterrupted stretch, individuals typically had a "first sleep", followed by a fairly lengthy wakened state, and then a "second sleep". Interestingly, this sort of bimodal sleep is the pattern normally shown by a wide range of other mammals, as well as birds and reptiles. (I’m not really positive if aardvarks sleep this way, but I imagine they do.)
A historian named Roger Ekirch concluded that the belief that a continuous eight-hour stretch of sleep is normal is a peculiarly modern phenomena, an apparent product of the industrial age. Using diaries, medical books, religious papers, etc., Ekirch established that before the nineteenth century people in Western Europe regarded waking in the middle of the night as commonplace and to be expected. People normally got up at this time, read a book, wrote in their diaries, interpreted their dreams, did chores, smoked, prayed, visited neighbors, even engaged in petty crime. He suggests that the invention of electric lighting made late night hours much more feasible and helps explain the waning of bimodal sleep in modern times. Anthropologists have further documented interrupted sleep patterns in a variety of non-Western populations, e.g., hunter-gatherers in Africa, herding tribes in Pakistan. Scientists speculate that there may be an evolutionary advantage to interrupted sleep since it leave people and animals less vulnerable to predators.
Age has been connected to bimodal sleep too. Sleep researchers find that deep sleep is much less common in people in their seventies and beyond, and bimodal sleep tends to become increasingly frequent. Ever since I found that out, I’ve been working on embracing bimodal sleep. Now that I’m retired and don’t have to worry about a work schedule, I look forward to being up and around for in the early morning hours. I go to the computer, check my e-mail, play a couple of games of computer solitaire, maybe work on a draft for my blog. By 4:30 or so my eyes start drooping again and it’s back to bed. The sheepdogs wake me promptly at 9, and it’s time to start the new day. This seems like a pretty good use of time. There’s a lot we can learn from the aardvarks.
SOURCES: www.nytimes.com, "Awakening to Sleep" (V. Klinkenborg, 1997); www.nytimes.com, "Sleep Disorder? Wake Up and Smell the Savanna" (R. Friedman, 2006); www.utne.com, "The No Wake Zone: Can't sleep through the night? You're not supposed to." (M. Wylie, Psychotherapy Networker, 2009); www.wikipedia.org, "Segmented sleep"