In lesson 1 you kept a sleep diary for one to two weeks. Now you will use it to set a "sleep window." This is a fixed span of time each night when you are allowed in bed.
Less time in bed to sleep better sounds odd. But it is one of the strongest parts of CBT for insomnia. It also needs the most care, so read the safety section first.
Key points
- Your sleep window starts at about the average sleep time from your diary, but never less than 5 hours.
- Keep the same wake-up time every day, including weekends. Go to bed only when your window opens.
- Each week, check your sleep efficiency (the share of time in bed you spend asleep) and adjust by about 15 minutes.
- Expect to feel more tired for the first one to three weeks. Do not drive or use risky tools when you feel drowsy.
- People with bipolar disorder, seizures, possible sleep apnea, or a job that needs full alertness should do this only with a clinician. Many older adults do better with the gentler "sleep compression" version.
Why this step matters
When sleep is poor, most people spend extra time in bed to catch up. The bed becomes a place for lying awake, and sleep gets thin and broken.
A sleep window does the opposite. It builds your sleep drive (the pressure to sleep that grows the longer you are awake). With more pressure, you fall asleep faster and wake less. Then you add time back, week by week.
The American Academy of Sleep Medicine suggests sleep restriction as a treatment on its own. It strongly recommends full CBT-I, which includes sleep restriction.1
Evidence: sleep restriction on its own Moderate evidence full CBT-I Strong evidence
A 2014 review found that it helps people fall asleep faster and spend less time awake at night. It added only a little to total sleep time.2
In a 2023 trial in England, 642 adults got either four short nurse sessions plus a sleep habits booklet, or the booklet alone. After six months, the nurse group scored about 3 points better on a 28-point insomnia scale, a medium-to-large effect.3 The gain held at 12 months.4
A 2025 guideline from Veterans Affairs and the Defense Department also strongly recommends CBT-I, ahead of sleep medicine.5
Before you start: is this safe for you?
Talk with a doctor or sleep specialist first, and do not try this alone, if any of these apply to you:
- Bipolar disorder. Losing sleep may set off mania or hypomania (periods of very high or irritable mood and energy).1 In one small trial, a version of CBT-I made for bipolar disorder eased insomnia and cut returns of mania or hypomania.6 It should be guided by your care team. See Living well with bipolar disorder.
- Seizures or epilepsy. Sleep loss can make seizures more likely.1,7
- Possible sleep apnea (loud snoring, gasping, or stopping breathing in sleep) or other sleep disorders. These should be checked and treated first.7 See Sleep apnea.
- Heavy daytime sleepiness already, such as dozing off while reading or watching TV.1
- A job where sleepiness is dangerous, such as driving for work or running heavy machinery.1,7
- You take sleep medicine. Keep taking it as prescribed. Talk with your doctor or pharmacist before changing anything.
Drowsy driving. In the first weeks, your reactions can be slower than usual.8 Very sleepy drivers can have "micro sleeps," blackouts of four or five seconds. If you cross lane lines or hit a rumble strip, pull over somewhere safe.9 Arrange rides when you can.
Falls. More than 1 in 4 older adults fall each year.10 Grogginess can add to that risk. Use a night light on the way to the bathroom, and sit on the bed edge a moment before standing. Ask your doctor or pharmacist whether any of your medicines can make you sleepy or dizzy.11 See also Preventing falls.
Two ways to set a window
Sleep restriction
Start the window close to your average sleep time right away. Faster results, but the first weeks are harder.
Sleep compression
Shrink your time in bed slowly, over about five weeks. Gentler and easier to stick with. Often a better fit for older adults and people with health problems.
In one trial of adults age 59 and older, all groups said they slept better, even a placebo (fake treatment) group. A year later, more people using sleep compression had a clear drop in time awake at night. Sleep lab tests showed no change.12 Sleep experts also suggest more flexible windows for older adults, and sometimes a short planned nap.7 For more on later life, see Sleep in later life.
How to set your sleep window
- Find your averages. From the diary in lesson 1, find your average total sleep time and your average time in bed. Use at least 7 nights, and up to 14.7
- Work out your sleep efficiency. Divide sleep time by time in bed, then multiply by 100. For example, 6 hours of sleep ÷ 8 hours in bed = 0.75, or 75%.
- Pick your wake-up time. Choose one you can keep all 7 days, and set an alarm. It does not move.7
- Set the window length. For sleep restriction, use your average sleep time, but never less than 5 hours.7 Some clinicians add 30 minutes to make the start easier.7
- Count back to find your bedtime. Wake at 6:30 a.m. with a 6-hour window? Your window opens at 12:30 a.m. Stay out of bed until then.
- Fill the evening. Plan calm activities for the extra time, out of bed. Staying up until your window opens can be hard.1 Try not to doze on the couch.
- Skip naps for now, unless your clinician has suggested a short, planned one.7
- Keep filling in your diary every morning. You will need it for the weekly check.
How to set a gentler window (sleep compression)
Find the gap between your average time in bed and your average sleep time. Divide it by 5. Each week, shorten your time in bed by that amount.12
Example: You spend 8 hours in bed but sleep 6. The gap is 120 minutes. Divided by 5, that is 24. So each week you cut about 25 minutes until you reach about 6 hours. Then use the weekly check below.
How to adjust your window each week
Once a week, average your sleep efficiency for the last 7 nights. Then follow this guide:7
| Your sleep efficiency | Most adults | Older adults (gentler cutoffs) |
|---|---|---|
| High | 90% or more: add 15 minutes | 85% or more: add 15 minutes |
| In the middle | 85% to 89%: keep the same window | 80% to 84%: keep the same window |
| Low | Under 85%: cut 15 minutes (never under 5 hours) | Under 80%: cut 15 minutes (never under 5 hours) |
Add time by going to bed earlier, not by sleeping later. Repeat each week until you feel rested by day and are mostly asleep while in bed.7
Try it this week
- Write your wake-up time and window start time on a card by the bed.
- Keep the same wake-up time all 7 days.
- At the end of the week, work out your sleep efficiency and use the table above.
What the first week feels like
Most people feel worse before they feel better. In one small study of 16 adults, people slept about 1 to 1½ hours less in the first weeks of a new window. They were sleepier in weeks 1 to 3, with slower reactions. By three months, alertness was back to normal and their insomnia had improved.8
This first week, you may feel tired, foggy or short-tempered. You may also fall asleep faster and lie awake less. Some nights will still be bad, and that is normal. The tiredness usually eases as your window grows.1
Common problems
I am so sleepy in the evening that I cannot stay up until my window starts.
Keep the lights on and do something mildly active, like folding laundry or a phone call. If you still cannot stay awake, ask your clinician about a longer window or sleep compression.
I fell asleep fast but woke up at 4 a.m. anyway.
Keep your wake-up time and give it a few weeks. If you lie awake and frustrated, get up and come back when sleepy. Lesson 3 explains this rule.
Can I sleep in on the weekend to catch up?
No. Sleeping in weakens your sleep drive for the next night. A steady wake-up time, 7 days a week, is the anchor of this program.7
I am at 5 hours and my sleep efficiency is still low.
Do not go below 5 hours. Some people sleep more than they think, so the diary looks worse than reality.7 A sleep specialist can check for other sleep problems.
My mood is getting worse, or I feel unusually high and wired.
Stop shortening your window and contact your doctor soon. A sharp rise in energy with little need for sleep can be a sign of mania. If you are thinking about suicide or harming yourself, call or text 988 any time. In an emergency, call 911.
Next step
In lesson 3: retraining bed for sleep, you will learn simple rules that teach your brain to link bed with sleep again. You can also return to lesson 1 or the CBT-I overview.
Sources
- Edinger JD, et al. Behavioral and psychological treatments for chronic insomnia disorder in adults: an American Academy of Sleep Medicine clinical practice guideline. J Clin Sleep Med, 2021. PMC
- Miller CB, et al. The evidence base of sleep restriction therapy for treating insomnia disorder. Sleep Med Rev, 2014. University of Oxford
- Kyle SD, et al. Clinical and cost-effectiveness of nurse-delivered sleep restriction therapy for insomnia in primary care (HABIT): a pragmatic, superiority, open-label, randomised controlled trial. Lancet, 2023. PubMed
- Kyle SD, et al. Nurse-delivered sleep restriction therapy to improve insomnia disorder in primary care: the HABIT RCT. Health Technol Assess, 2024. DOAJ
- US Department of Veterans Affairs and Department of Defense. The management of chronic insomnia disorder and obstructive sleep apnea: VA/DoD clinical practice guideline, provider summary (version 3.0). VA/DoD, 2025. VA (PDF)
- Harvey AG, et al. Treating insomnia improves mood state, sleep, and functioning in bipolar disorder: a pilot randomized controlled trial. J Consult Clin Psychol, 2015. eScholarship
- Spielman AJ, Yang CM, Glovinsky PB. Sleep restriction therapy. In: Behavioral Treatments for Sleep Disorders. Elsevier, 2011. Chapter (PDF)
- 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. University of Glasgow
- National Highway Traffic Safety Administration. Drowsy driving: avoid falling asleep behind the wheel. NHTSA. NHTSA
- Centers for Disease Control and Prevention. Facts about older adult falls. CDC, 2026. CDC
- Centers for Disease Control and Prevention. Preventing falls and hip fractures. CDC, 2026. CDC
- Lichstein KL, et al. Relaxation and sleep compression for late-life insomnia: a placebo-controlled trial. J Consult Clin Psychol, 2001. Full text (PDF)
Education only. This page is general information written from the sources listed. It is not medical, legal or financial advice and does not replace a doctor, therapist or lawyer who knows your situation. How we write and check pages.