How to keep a sleep diary (and what to write in it)

The GP asks how many nights a week it happens. You say most, probably. They ask how long you're awake for, and you hear yourself say an hour, maybe two, and realise you're guessing.

The nights blur. Tuesday was bad, but was Wednesday? The one where you got up for the loo at 4am, or was that the week before?

Ten minutes later you're back in the car park with a leaflet. The leaflet says to keep a sleep diary.

You're not vague; nobody remembers sleep well. A 2012 review in Psychological Bulletin found that people with insomnia tend to overestimate how long they took to fall asleep and underestimate how long they slept. The lab instruments disagree with them, consistently.

A diary won't fix that. But it stops the nights blurring into one, and that's the half a GP needs.

Without one, the ten-minute appointment goes nowhere, and the next is three weeks away.

What a sleep diary is

It's a record you write each morning about the night before, in your own estimates. A sleep log is the same thing; some are grids you shade, some are columns you fill, and the questions underneath are identical.

It isn't a tracker. A wrist tracker guesses sleep from movement and pulse, and can call lying still asleep. The diary records what you experienced, and clinics regard it as the standard for that, which is why the leaflet asks for one.

The standard research version comes from a 2012 paper in the journal Sleep. A group of insomnia researchers agreed nine core questions, then tested the form on focus groups: good sleepers, people with insomnia and people with sleep apnoea.

What to record

You don't need a printed form. Rule a sheet into these columns tonight, one row per night, and it will do everything a clinic's version does.

1. Time you got into bed. Not the time you meant to. The gap between this and the next column is reading and scrolling, and it all counts as time in bed.
2. Time you turned the light off to sleep. This is the moment you actually tried. Everything after it is the night proper.
3. How long it took to fall asleep. An estimate, in round minutes. Five, twenty, forty, an hour. Nobody can time this and nobody should try.
4. How many times you woke. Count the ones you remember. A quick turn-over doesn't count; a trip to the loo does.
5. How long you were awake in total. Add the wakings up roughly. This is the number you've been guessing at in appointments.
6. Time of your final waking. The moment you were awake for good, whether the alarm did it or not.
7. Time you got out of bed. The gap between this and the last column matters too; forty minutes of lying awake under the duvet is forty minutes of lying awake.
8. Naps and dozes. When and how long. The sofa at 9pm counts, and it's the one people forget.
9. Caffeine and alcohol. What, when and roughly how much. The NHS lists both among the common causes of broken sleep, and the timing is often the whole story.
10. How you feel. A quality mark out of five for the night, and a word for the day: fine, foggy, wrecked, or one of your own. The NHS asks for how you felt the next day, and the Royal College of Psychiatrists says to judge your sleep by the day, not the hours.
11. A comments line. The line that explains the night: a cold, an argument, the neighbour's party, a late shift. The people who tested the standard diary insisted on this box.

How to fill it in

Do it in the morning, within an hour of getting up, with a cup of something in reach. The standard diary's instructions say the same. By evening you'll have rewritten the night in your head.

Estimate; don't measure. The diary is not a reason to check the clock at 3am, and clock-watching makes getting back to sleep harder. If you wake and think "about half an hour", write half an hour.

Keep the sheet out of the bedroom, in the kitchen or by the kettle. The Mental Health Foundation's diary gives the same instruction, and the reason is simple: the sheet is a small piece of homework, and homework belongs in the kitchen.

If you miss a morning, leave the row blank. A gap is more honest than a guess filled in on Thursday.

How long to keep it

Two weeks. One bad week proves nothing; two catches the weekend, the late nights, the ordinary nights and the pattern between them. The Mental Health Foundation's diary runs for 14 days, and the standard form fits a week to a page, so that's two pages.

Then stop, unless a clinic asks for more. The pattern is usually clear by then.

How a GP uses it

First, to see which problem you have. Taking an hour to fall asleep, waking at 3am and waking at 5am for good are three different problems. We've set out why falling asleep and staying asleep differ.

Second, to do one sum: hours asleep divided by hours in bed. That's your sleep efficiency, and it's one of the numbers a sleep clinic watches most.

The Royal College of Psychiatrists describes a bedtime method with a target: asleep within about 20 minutes, and awake for no more than about 20 minutes in the night. Your diary tells you if you're there.

Third, to find the cause hiding in the columns. The 4pm coffee two days running, the wine on the nights with three wakings, the nap that pushed bedtime back, the Sunday lie-in that spoiled Monday. We've written about how late caffeine can go and why 3am is such a common waking time.

The NHS says to see a GP if changing your habits hasn't helped and the trouble has gone on for months. Arrive with the two pages and the appointment starts in the middle rather than the beginning.

What the diary gets wrong

The diary records the night as you experienced it, not the night as it was. That 2012 review weighed 13 explanations for the gap; the best supported were brief wakings, worry, and sleep that feels like being awake. So your diary may say less sleep than you got.

That's fine, and clinics know it. Your experience of the night is what they're trying to change. But if two weeks of writing it down leaves you more anxious about sleep rather than less, say so at the appointment; that's useful information too.

The sheet by the kettle is the real work, and it starts tomorrow morning.