Is it normal to wake up at night?

Yes. Short awakenings are a normal part of sleep in healthy people, and the time spent awake after first falling asleep rises with age. Night waking becomes a problem when it is frequent, hard to recover from, and comes with distress or daytime impairment. ^[1][5]

What the research says

Pooled recordings from 65 studies of 3,577 healthy people aged 5 to 102 show that some waking is simply part of adult sleep: time awake after falling asleep, and time to fall asleep, rise with age, while total sleep, sleep efficiency and deep sleep fall; how strictly participants were screened for health problems changed how large those effects looked. ^[1] An expert panel that reviewed 277 studies agreed that awakenings longer than five minutes, time awake after sleep onset, sleep latency and sleep efficiency are appropriate markers of sleep quality across the lifespan, with weaker agreement on sleep stages and naps. ^[2] Whether we were ever meant to sleep in one block is less clear. Three groups living without electricity slept for 6.9 to 8.5 hours a night, with 5.7 to 7.1 hours of actual sleep, "not interrupted by extended periods of waking". ^[3] Yet when healthy volunteers lived with 10-hour days instead of 16, their sleep expanded and usually split into two bouts, with one to three hours awake between. ^[4]

The studies behind this

• Normative sleep data (Ohayon, 2004): a meta-analysis of 65 studies, 3,577 healthy people aged 5 to 102, measured with overnight recordings or wrist actigraphy. In adults, wake after sleep onset and the time taken to fall asleep increased with age, while total sleep time, sleep efficiency and deep sleep decreased. The free sleep efficiency calculator shows what a few nights of waking do to the number. How strictly participants had been screened for health problems changed the size of the effects. ^[1]
• Sleep quality consensus (Ohayon, 2017): an expert panel reviewing 277 studies agreed that sleep latency, awakenings longer than 5 minutes, time awake after sleep onset and sleep efficiency are appropriate indicators of sleep quality across the lifespan. Agreement was weaker on sleep stages and naps. ^[2]
• Pre-industrial societies (Yetish, 2015): in three groups living without electricity, sleep periods lasted 6.9 to 8.5 hours with 5.7 to 7.1 hours of actual sleep, and were "not interrupted by extended periods of waking". ^[3]
• Photoperiod experiment (Wehr, 1992): when healthy volunteers lived with a 10-hour day length instead of 16, their sleep expanded and usually split into two bouts several hours long, with a 1 to 3 hour waking interval between. ^[4]

Why do we wake at all?

Recordings of healthy adults include some time awake after sleep onset, which is why researchers measure it as a normal variable of sleep rather than treating any waking as an error. ^[1][2] The amount tends to grow with age, which is covered in sleep and ageing.

What about "first sleep" and "second sleep"?

A popular idea says people once slept in two blocks with a waking period between, and that modern night waking is simply a return to that pattern. The research is more mixed than that:

• Lab evidence exists. Under a short day length, volunteers did sleep in two bouts. ^[4]
• Field evidence does not clearly support it. In three pre-industrial societies measured with modern tools, sleep was not interrupted by extended waking periods. ^[3]

We would not conclude either way from this. What both studies show is that natural sleep depends on light, temperature and timing, and that night waking can be shaped by the environment. ^[3][4]

When does waking at night become insomnia?

Insomnia disorder is defined by dissatisfaction with sleep, difficulty initiating or maintaining sleep, and distress or impairment during the day. ^[5] In a Canadian survey of 2,000 adults, 40.2% had at least one insomnia symptom (trouble falling or staying asleep, or waking too early) three or more nights a week, but 13.4% also had the distress or daytime impairment needed to meet full criteria. ^[6] So many people wake at night; far fewer have a disorder. What chronic insomnia is, and how it is assessed, has its own article.

Signs that it is worth talking to a doctor:

• You wake often and cannot return to sleep, for months.
• You feel unwell or impaired in the day because of it.
• You have symptoms such as loud snoring or breathing pauses. The European guideline names breathing-related and limb-movement disorders as ones to evaluate if suspected. ^[7]

What helps?

For persistent insomnia, CBT-I is the first-line treatment in the European guideline. ^[7] We do not publish scheduling rules here, because they depend on your own sleep records. For the night itself, what the research says about lying awake at 3am is covered separately.

Where the evidence is thin

• The normative data combine many small studies with different methods, and the apparent size of age effects depended on how carefully participants were screened for health problems. ^[1]
• The expert panel's consensus was about what makes a sleep-quality indicator appropriate, not a fixed number of awakenings you should have. We have not given a number for that reason. ^[2]
• The two-sleep question is unresolved. ^[3][4]

If night waking is affecting you, Small Hours can help you track it and work through CBT-I. You can sign up at trysmallhours.com.

General education, not medical advice.