Why Waking Up in the Middle of the Night Might Be Normal

Segmented sleep — characterized by two main sleep bouts per night — has fascinated researchers and sleep enthusiasts alike.

By Sasha Takoo 03.31.26 5 min read

Sleep scientists and historians have long debated whether the modern recommendation of a continuous 7–9 hours of sleep (called monophasic sleep) truly reflects how humans naturally sleep. One alternative pattern that has gained attention — both in academic literature and public discussion — is segmented sleep, a form of biphasic sleep in which sleep is spread across two distinct periods in a 24‑hour cycle.

In this article, we explore what segmented sleep is, what research suggests about its history and physiology, and whether it could align with modern health needs.

What Is Segmented Sleep?

Segmented sleep refers to sleeping in two separate bouts instead of one consolidated block during the night. Historically, this meant falling asleep after dusk, waking for a period in the middle of the night, and then returning to sleep until dawn. In academic literature, this pattern is often described as biphasic sleep — a subset of polyphasic sleep (sleep occurring in multiple bouts) with exactly two major sleep episodes per day. (Leviathan Encyclopedia)

This pattern is distinct from other sleep variations such as naps or fragmented sleep due to sleep disorders; segmented sleep is intended and structured rather than a sign of pathology.

Historical Perspectives: Was Segmented Sleep “Natural”?

The idea that segmented sleep was the historical norm stems largely from the work of historian Roger Ekirch. Drawing on medieval and early modern archival sources, Ekirch identified frequent references to “first sleep” and “second sleep,” with an intervening period where people reportedly engaged in quiet activities. (National Geographic)

These references appear in diaries, medical texts, and literature — often described matter‑of‑factly as a normal nightly pattern rather than an exception. (Google Sites) Supporters of this view suggest that segmented sleep may have been widespread before artificial lighting and industrial timetables enforced consolidated night rest.

However, not all evidence supports a universal historical pattern. Recent analysis questions whether segmented sleep was truly dominant in pre‑industrial times, arguing that distinctions in historical texts may reflect continuous sleep with interrupted phases rather than two clearly separated sleep periods. (Cambridge University Press & Assessment)

Moreover, anthropological studies of pre‑industrial societies near the equator — where night length changes little seasonally — have found that continuous sleep of around 6–7 hours is common, suggesting that strict segmented sleep may not have been human default globally. (ScienceDirect)

Taken together, historical and anthropological evidence suggests that sleep patterns were more diverse than once thought and likely influenced by geography, season, and cultural practice.

Physiology of Segmented Sleep

From a biological perspective, sleep is regulated by two key systems:

Circadian rhythms, driven by the body’s internal clock in the brain’s suprachiasmatic nucleus, which cycles with light‑dark cycles.
Homeostatic sleep pressure, a build‑up of physiological need for sleep the longer we remain awake.

Contemporary sleep science acknowledges that humans have flexible sleep architecture shaped by these systems. Electroencephalography (EEG) studies show that even during a typical night of consolidated sleep, REM and non‑REM phases fluctuate in a cyclical pattern. This suggests underlying ultradian rhythms that could support more than one sleep episode per 24‑hour cycle. (PubMed)

In segmented sleep, the middle period of wakefulness may align with natural low points in sleep pressure, allowing the body and brain to transition back into a second sleep period without major physiological conflict. However, evidence on its physiological advantage or disadvantage compared with consolidated sleep remains limited and mostly theoretical at this point.

Modern Research and Health Implications

A 2025 review in Sleep Medicine explored biphasic sleep as a potentially natural and culturally valid alternative to consolidated sleep in some individuals and contexts. (ScienceDirect) The authors highlighted that:

Biphasic sleep may help offset sleep loss in certain groups (e.g., shift workers, caregivers).
Mid‑night wakefulness — often seen as insomnia — could be normal for some chronotypes.
A more personalized sleep model might better accommodate individual needs.

However, the review also emphasized that more research is needed to understand how such patterns affect long‑term health outcomes like metabolism, cognitive function, and mood.

Importantly, many controlled sleep studies still recommend consolidated sleep for most adults, particularly because fragmentation of sleep due to disorders (e.g., sleep apnea) is known to reduce sleep quality. Segmented sleep that *emerges naturally — without significant sleep maintenance insomnia — may not carry the same risks, but distinguishing the two remains a challenge.

Is Segmented Sleep Right for You?

Given the current evidence:

Segmented sleep might be normal for some individuals and not inherently harmful.
Scientific support for improved health outcomes is limited and not conclusive.
Cultural and environmental context influences how individuals experience segmented patterns.

If you notice natural mid‑night wakefulness followed by restful second sleep without daytime impairment, this could reflect your personal chronotype rather than insomnia. However, if wakefulness leads to anxiety or poor sleep quality, consolidated sleep remains the standard clinical recommendation.

Key Takeaways

Segmented sleep divides nightly rest into two periods and is a form of biphasic sleep. (Leviathan Encyclopedia)
Historical records suggest segmented sleep was common in some pre‑industrial contexts, but evidence is nuanced. (National Geographic)
Biological rhythms support flexibility in sleep timing, but the benefits of segmented vs. consolidated sleep are not fully established. (PubMed)
Modern research encourages individualized approaches to sleep rather than a strict one‑size‑fits‑all model. (ScienceDirect)