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ReSomnia

Guide · 8-minute read

Sleep restriction, explained step by step

Sleep restriction means limiting your time in bed to the time you actually sleep, so that sleep becomes deeper and more continuous again, then widening that window each week based on your sleep efficiency. It is one of the most effective components of CBT-I[6][7].

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By Andy Leleux, sleep technologist · Updated on 27 October 2026

Key points

  • You start by keeping a sleep diary for one to two weeks to find out how much you really sleep[2].
  • The sleep window sets a bedtime and a wake-up time, the same seven days a week[2].
  • It is adjusted each week: at 90% efficiency or more it widens; below 85% it shrinks[3].
  • The first two to three weeks are tiring; that is expected and temporary[3]. Not everyone should do it without medical advice[4][5].

The principle

When you sleep badly, it's natural to spend more time in bed to “catch up”: going to bed earlier, lingering in the morning. The result is long hours lying awake, and fragmented sleep.

Restriction turns the problem on its head: by cutting your time in bed down to the time you actually sleep, your drive to sleep builds and sleep becomes more compact, deeper and less broken. Once sleep has consolidated, the window is gradually extended[1][2].

Step 1: keep a sleep diary for one to two weeks

Each morning, note when you went to bed, how long it took you to fall asleep, any awakenings, and when you woke up and got up. After one to two weeks, you'll know your average sleep time and your sleep efficiency (time asleep divided by time in bed)[2].

Step 2: work out your sleep window

In the standard protocol, your starting time in bed matches the average sleep time in your diary[3][4]. Protocols set a minimum, most often 5 hours, to avoid cutting too far[2][3][9].

Example. You spend 8 hours in bed but sleep only 5 hours 30 minutes on average: your efficiency is 69%. With a 30-minute margin, your starting window is 6 hours. If you get up at 7 am, you don't go to bed before 1 am.

Before
8 h in bed · 5 h 30 of sleep · 69% efficiency
With a sleep window
6 h in bed · 5 h 20 of sleep · 89% efficiency
  • In bed
  • Asleep
The sleep window, before and after. With 6 hours in bed instead of 8, less time is spent awake in bed and sleep becomes more compact. Illustrative example, based on the calculation above.

The ReSomnia approach

The app adds a 30-minute margin to your average sleep time and never goes below 5 hours (5 hours 30 minutes with more cautious settings, for example from age 65 or during pregnancy). This is more flexible than the standard protocol, as a precaution, in line with the margin described by the method's authors[2] and the wider windows advised for people who are sleepy[3].

Step 3: stick to your times

  • A fixed wake-up time, seven days a week, weekends included: this is the anchor of the method[2].
  • No going to bed before your set time, even if you're tired: wait until that time, then go to bed if you feel sleepy.
  • No naps during the restriction phase, to save your drive to sleep for the night[2].
  • If sleep doesn't come, get up and go back when you feel sleepy again: that's stimulus control, which goes hand in hand with restriction.

Step 4: adjust each week

Each week, look at your sleep efficiency over the last seven nights[3]:

  • 90% or more: the window widens by 15 minutes.
  • 85 to 89%: it stays the same.
  • Below 85%: it shrinks by 15 minutes, without going under the minimum.

For older people, the method's authors suggest more flexible thresholds (85 and 80%)[2]. You stop widening once your sleep time and satisfaction are good enough[4]. A programme generally lasts six to eight weeks[3].

The first few weeks

The first two to three weeks are the hardest. In a small laboratory study (16 patients), measured total sleep fell by about 1 to 1.5 hours during sleep restriction, and daytime sleepiness and attention lapses increased. At three months, sleepiness and alertness had returned to their starting level[3].

In the largest trial in general practice (642 people), restriction did not lead to more accidents, falls or near misses than sleep hygiene advice, in patients without epilepsy, bipolar disorder, known sleep apnoea or shift work[8].

Take care when driving

If you feel sleepy, don't drive and avoid anything dangerous. Severe sleepiness is not “normal”: it is a reason to widen your window and talk to your doctor or clinician.

When not to do it on your own

Guidelines advise against restriction without medical supervision if you have epilepsy, bipolar disorder or a tendency to mania, excessive daytime sleepiness, or a job where alertness is critical (professional driving, machinery)[4][5]. Untreated sleep apnoea, pregnancy or night work also call for medical advice before you start.

With ReSomnia

  • The app calculates your starting window from your diary, then suggests an adjustment each week based on your efficiency.
  • Before you start, a few safety questions pick up situations where medical advice is needed.
  • During restriction, you are asked a question about sleepiness each morning: if you are sleepy, the window is extended by 30 minutes, and it is paused if the sleepiness keeps happening or occurs while driving.
  • If you wish, your clinician can follow your diary and your window between sessions.

Frequently asked questions

How long does sleep restriction last?

Usually six to eight weeks, long enough to consolidate your sleep and then widen the window to a satisfactory length. After that, you keep adjusting with the diary if needed.

What if I can't fall asleep at my set time?

Don't lie there battling it: get up, do something quiet in dim light, and go back when you feel sleepy again. Keep your wake-up time, even after a bad night.

Can I nap?

During the restriction phase, it is best avoided: a nap reduces your drive to sleep in the evening. If you are really sleepy, don't drive and talk to someone about it: it's a sign your window needs widening.

Why keep the same hours at weekends?

Because a regular wake-up time resets your body clock and keeps your drive to sleep building at the same hour. A lie-in on Sunday pushes the next night back.

Is sleep restriction dangerous?

It is tiring at first, temporarily, and calls for care when driving. Without medical supervision, it isn't suitable if you have epilepsy, bipolar disorder, excessive sleepiness or a high-risk job.

Read and do next

Sources

  1. [1] Spielman AJ, Saskin P, Thorpy MJ. Treatment of chronic insomnia by restriction of time in bed. Sleep. 1987;10(1):45-56. PubMed
  2. [2] Spielman AJ, Yang CM, Glovinsky PB. Sleep Restriction Therapy. In: Behavioral Treatments for Sleep Disorders. Academic Press; 2011. Link
  3. [3] Kyle SD, et al. Sleep restriction therapy for insomnia is associated with reduced objective total sleep time, increased daytime somnolence, and objectively impaired vigilance. Sleep. 2014;37(2):229-237. PubMed
  4. [4] Edinger JD, et al. Behavioral and psychological treatments for chronic insomnia disorder in adults: an AASM clinical practice guideline. J Clin Sleep Med. 2021;17(2):255-262. PubMed
  5. [5] Riemann D, et al. The European Insomnia Guideline: an update on the diagnosis and treatment of insomnia 2023. J Sleep Res. 2023;32(6):e14035. PubMed
  6. [6] Furukawa Y, et al. Components and delivery formats of cognitive behavioral therapy for chronic insomnia in adults. JAMA Psychiatry. 2024;81(4):357-365. PubMed
  7. [7] Steinmetz L, et al. Network meta-analysis examining efficacy of components of cognitive behavioural therapy for insomnia. Clin Psychol Rev. 2024;114:102507. PubMed
  8. [8] Kyle SD, et al. Clinical and cost-effectiveness of nurse-delivered sleep restriction therapy for insomnia in primary care (HABIT). Lancet. 2023;402(10406):975-987. PubMed
  9. [9] Kyle SD, et al. Towards standardisation and improved understanding of sleep restriction therapy for insomnia disorder: A systematic examination of CBT-I trial content. Sleep Med Rev. 2015;23:83-88. PubMed

This guide provides information and does not replace advice from a doctor or psychologist. If you are in distress, call your local crisis line at any hour: 1813 or 0800 32 123 in Belgium, 116 123 in the UK and Ireland, 988 in the US. In immediate danger, call 112 in Europe or your local emergency number.

Your sleep window, worked out for you.

ReSomnia calculates your window from your diary, adjusts it each week and looks out for your safety during the first few weeks. Free, with your clinician if you wish.

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The app itself is in French for now. English is on the way.