Why You Wake Up at 3 a.m. and Why Your Body Might Be Doing It On Purpose
“The sleep disorder isn’t you. It might be the schedule we’ve all been handed since the Industrial Revolution.”
Most people who find themselves wide awake at 2 or 3 in the morning assume something is broken. Their mind races to anxiety, aging, cortisol, blue light, too much coffee. But there’s another possibility — one that historians and sleep scientists have been quietly assembling evidence for — that your body is doing exactly what bodies have done for most of human history.
Before the 19th century, a full night of rest wasn’t one continuous block of eight hours. It was two. People slept a “first sleep” of roughly four hours, woke for an interval they called “the watch,” and then returned to a “second sleep” until morning. This wasn’t a fringe habit or a sign of illness. It was simply how the human night worked.
We know this in unusual detail thanks to historian Roger Ekirch, whose 2001 paper in the American Historical Review and 2005 book At Day’s Close: Night in Times Past drew on more than 2,000 references to first and second sleep across centuries of diaries, court records, medical texts, and literature from medieval Europe to the early industrial era.[1] The sources were explicit: people planned around this wakeful interval. They used it for prayer, for reading by candlelight, for quiet conversation with a bed partner, for tending to a child.
“References to the first sleep began to disappear from the historical record in the late 17th century in the cities of northern Europe — precisely as artificial street lighting began to spread.”PARAPHRASED FROM EKIRCH, A.R. (2005). AT DAY’S CLOSE: NIGHT IN TIMES PAST.
What’s striking is that this pattern appears to be encoded in our biology, not just our history. In 1992, psychiatrist Thomas Wehr at the National Institute of Mental Health ran an experiment in which participants were kept in darkness for 14 hours a night for four weeks — essentially simulating pre-industrial light conditions. Within a few weeks, a clear pattern emerged: nearly all participants began sleeping in two distinct blocks, separated by one to three hours of quiet wakefulness.[2] Wehr noted that during this waking interval, participants showed elevated levels of prolactin — a hormone associated with a calm, meditative state that is distinct from both normal wakefulness and sleep. They weren’t anxious. They were peaceful.
This matters because it directly challenges how modern sleep medicine often classifies middle-of-the-night waking. When people report waking between 1 and 4 a.m. and struggling to fall back asleep, the standard framework is to treat it as a symptom — of anxiety, depression, or a form of insomnia called “sleep maintenance disorder.” And in many cases, that’s correct. But Wehr’s findings suggest there is a subset of people for whom this waking is simply the body reverting to an ancient rhythm, particularly in winter months or when stress is low.
WHAT THE RESEARCH ACTUALLY SHOWS
- Ekirch documented 2,000+ historical references to “first” and “second” sleep — not as a disorder, but as the normal structure of the pre-industrial night. [Ekirch, 2001; 2005]
- Wehr’s 1992 NIH isolation study found participants spontaneously reverted to bimodal sleep within weeks of being removed from artificial light. [Wehr, 1992]
- The wakeful interval in Wehr’s study lasted 1–3 hours and was accompanied by elevated prolactin — a calm, non-anxious state. [Wehr, 1992]
- The disappearance of segmented sleep correlates with the spread of artificial lighting in European cities from the late 1600s onward. [Ekirch, 2005]
- Russell Foster’s research at Oxford on circadian biology supports the idea that light exposure is the primary driver suppressing the bimodal pattern in modern populations. [Foster, 2012]
The Industrial Revolution is what finally erased the two-sleep model from everyday life. When factory shifts required workers to be alert at fixed hours, sleep had to become a single, efficiently-compressed block. Artificial lighting extended the evening, pushing bedtime later and later until the “first sleep” had no room to begin early enough for the natural gap to exist. By the early 20th century, the idea of sleeping in two halves had become so foreign that doctors began pathologizing it.[1]
None of this is a prescription to start treating your 3 a.m. waking as virtuous. If it leaves you impaired the next day, if it’s driven by racing thoughts or anxiety, or if it’s recent and unexplained, speaking with your GP or a sleep specialist is still the right move. Genuine sleep disorders are real and treatable, and this history doesn’t change that.
But if you wake in the early hours feeling calm — alert in a quiet way, not distressed — and you lie there waiting anxiously for the second sleep that used to come naturally? It might help to know that the waiting itself was once the point. The night used to have a middle. Yours might simply remember it.
SOURCES & REFERENCES
- Ekirch, A.R. (2001). Sleep we have lost: Pre-industrial slumber in the British Isles. American Historical Review, 106(2), 343–386. / Ekirch, A.R. (2005). At Day’s Close: Night in Times Past. W.W. Norton & Company.
- Wehr, T.A. (1992). In short photoperiods, human sleep is biphasic. Journal of Sleep Research, 1(2), 103–107. doi:10.1111/j.1365-2869.1992.tb00019.x
- Foster, R.G. (2012). Circadian rhythms and sleep: A scientific overview. Philosophical Transactions of the Royal Society B, 367, 3221–3226.
Photo by Nubelson Fernandes on Unsplash
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