Second sleep refers to the second portion of a two-part sleep pattern that was common across Europe before the industrial era. People would fall asleep a couple of hours after dark, wake up around midnight for one to two hours, then go back to sleep until dawn. That return to sleep was “second sleep,” and the earlier portion was “first sleep.” This wasn’t a sleep disorder or an unusual habit. For centuries, it was simply how humans slept.
How the Two-Sleep Pattern Worked
The typical schedule looked something like this: people went to bed around 9 or 10 p.m., slept for three to four hours, then woke naturally around midnight. They stayed awake for an hour or two before drifting back into their second sleep, which lasted until morning. Bedtime wasn’t dictated by the clock but by whether there was anything left to do after dark. Without electric light, the answer was usually no.
The wakeful period in between, sometimes called “the watch,” wasn’t spent lying in bed frustrated. People used it productively or peacefully. They prayed, reflected on dreams, talked with a bed partner, tended the fire, or even visited neighbors. It was a recognized, structured part of the night, not a disruption to it.
Centuries of Evidence
Historian A. Roger Ekirch was the first to piece together the widespread practice of segmented sleep in pre-industrial Europe. He found references spanning more than two thousand years. The earliest comes from Homer’s Odyssey, written in the 8th century BC. From there, the trail runs through works by the Roman historian Livy, the Roman poet Virgil, the Greek biographer Plutarch in the first century AD, and the Greek traveller Pausanias in the second century AD.
The references keep appearing through the medieval period and beyond. Geoffrey Chaucer mentions first sleep in The Canterbury Tales, written between 1387 and 1400. William Baldwin’s Beware the Cat from 1561 includes it. Even folk ballads reference the pattern casually, like “Old Robin of Portingale,” which instructs: “And at the wakening of your first sleepe, You shall have a hot drink made, And at the wakening of your next sleepe, Your sorrows will have a slake.” These weren’t explanations of an exotic custom. They were offhand mentions, the kind of language people use when describing something everyone already knows about.
What Happens in the Body During the Gap
The wakeful period between sleeps isn’t just a cultural artifact. It has a hormonal signature. People who sleep in two segments release a surge of prolactin before waking in the middle of the night. Prolactin is a hormone most associated with breastfeeding, but it plays a broader role in regulating mood, immune function, and reproductive hormones. That prolactin surge triggers a cascade that ends with the release of progesterone, which brings on the drowsiness that pulls you into second sleep.
In people who sleep in a single consolidated block, this prolactin surge is much smaller. Instead, the body distributes smaller amounts of prolactin throughout the day. Some researchers have suggested this trickle pattern is less ideal than the concentrated nighttime release, though how much this matters for long-term health is still debated.
Why We Stopped Sleeping This Way
The shift from two sleeps to one tracks closely with the spread of artificial lighting in the late 19th century. As gas lamps and then electric lights made cities bright after dark, the night became useful. People stayed up later, filled the evening hours with socializing and work, and compressed their sleep into a single block to fit the demands of industrial schedules. The Victorian era saw night increasingly treated as productive space rather than a long, quiet stretch to be divided between two sleeps.
By the early 20th century, references to “first sleep” and “second sleep” had essentially vanished from everyday language. Within a few generations, the concept was forgotten entirely, replaced by the assumption that healthy sleep means one unbroken stretch of seven to nine hours.
Second Sleep vs. Insomnia
Here’s where the history gets personally relevant. The appearance of sleep maintenance insomnia as a medical concept in the late 19th century coincides almost exactly with the disappearance of two-sleep references from daily life. Sleep maintenance insomnia is the kind where you fall asleep fine but wake up in the middle of the night and can’t get back to sleep for a while. That description sounds a lot like the gap between first and second sleep.
Some sleep researchers now believe that for certain people, waking in the middle of the night isn’t a malfunction. It may reflect a natural preference for split sleep that modern society no longer accommodates. The expectation that you should sleep straight through from 11 p.m. to 7 a.m. can create anxiety when you wake at 2 a.m., and that anxiety makes it harder to fall back asleep. Knowing that your body might simply be following an older pattern can itself reduce the stress enough to make the wakeful period feel normal rather than alarming.
That said, there’s an important distinction between waking calmly for an hour and returning to sleep easily versus lying awake for hours feeling wired, anxious, or unable to function the next day. The first pattern resembles historical second sleep. The second pattern is more likely genuine insomnia worth addressing.
Is Segmented Sleep a Good Idea Today?
The appeal of reclaiming second sleep is understandable, but modern life creates a practical problem: most people don’t have a 10- to 12-hour window available for sleep. If you go to bed at 9 p.m., stay awake from midnight to 1 a.m., then sleep again until 6 a.m., you can get a full night’s worth of rest in two pieces. But if your schedule only allows you to be in bed from 11 p.m. to 6:30 a.m., splitting that into two segments with a wakeful gap in between means you’re simply not sleeping enough.
This is the core concern raised by sleep scientists studying polyphasic and biphasic schedules in modern contexts. When segmented sleep compresses total sleep time below what your body needs, the consequences are real: impaired memory and reaction time, worsened mood, increased irritability, and steeper declines in performance throughout the day. A National Sleep Foundation consensus panel found that chronic sleep deficiency from fragmented schedules is associated with higher risk of cardiovascular disease, diabetes, accelerated cognitive decline, and shortened lifespan. Depression ratings increased the longer people stayed on reduced polyphasic schedules, and sleep inertia (that groggy, disoriented feeling after waking) became worse and more frequent with each sleep episode on a background of insufficient rest.
The key variable isn’t whether sleep is split into one block or two. It’s total sleep time. Pre-industrial people could afford two sleeps because they spent 10 or more hours in bed. If you can do the same and still get seven to nine hours of actual sleep across both segments, splitting the night likely poses no problem. If splitting the night means sleeping less overall, it will cost you.