How to Keep a Sleep Diary That Shows What Is Really Going On

A sleep diary is a short daily record of when you went to bed, roughly when you fell asleep, when you woke and how you felt the next day. Kept for one to two weeks, it turns a vague sense of being tired into a pattern you can actually see. It costs nothing, takes a couple of minutes a day and is often the first thing a GP will ask for when someone mentions trouble sleeping.

Why bother writing it down?

Memory is a poor witness to sleep. A single bad night can colour how you remember a whole week, while a run of slightly short nights can go unnoticed. Writing entries close to the time removes some of that guesswork and helps with questions such as:

• Am I actually sleeping as little as I think, or just spending a long time in bed awake?
• Do late meals, evening workouts, alcohol or caffeine line up with worse nights?
• Is my bedtime drifting later on certain days of the week?
• How different are workdays and days off?

It also gives you something concrete to compare against general advice, such as the ranges in the guide on how many hours of sleep adults need.

What to record

Keep it simple enough that you will still be filling it in on day ten. Split the entries into a quick evening note and a slightly longer morning note.

How to keep it going

1. Choose one format and stick with it. A notebook on the bedside table, a printed grid or a notes app all work. Paper has the advantage of keeping your phone out of reach.
2. Fill in the morning part within an hour of waking, before the day blurs the details.
3. Estimate, do not measure, during the night. Checking the clock every time you stir tends to make wakefulness worse. A rough guess in the morning is good enough.
4. Keep going for at least a week, and two if you can, so that both workdays and days off are included.
5. Change nothing else at first. The first week is for observing. Experiments come afterwards.

Reading the results

At the end, lay the days side by side and look for a few things.

Time in bed versus time asleep

Subtract the time you think you fell asleep and any long wakings from the total time in bed. A large gap between the two, night after night, is worth mentioning to a GP, because there are structured approaches that help with it.

Regularity

Bedtimes and wake times that swing by several hours between weekdays and weekends can leave you feeling jet-lagged without ever leaving the city. Steadier times often help on their own.

Links with the day before

Do the poor nights follow late coffee, a heavy evening meal, alcohol or a late intense workout? Do the better ones follow a walk outdoors or an earlier finish at work? Patterns are clues, not proof, but they suggest what to try first.

Short or broken nights

If the totals show you are regularly well under seven hours, an earlier lights-out is usually the first thing to try. If the nights are long enough but broken, the notes in your "anything unusual" column often point to the reason. Early waking on bright mornings suggests looking at blackout curtains for better sleep, while repeated wakings on busy streets point towards the guide on sleeping through city noise.

Mistakes that blur the picture

• Filling in several days at once from memory
• Recording only the bad nights
• Treating a wearable's sleep score as more precise than it is; it can be a useful extra column, but it is still an estimate
• Letting the diary become a source of worry; if it starts to keep you up, simplify it or pause

Taking it to an appointment

Bring the diary if you see a GP about sleep. Mention any loud snoring or pauses in breathing a partner has noticed, low mood, pain, frequent trips to the toilet at night, strong urges to move your legs in the evening, or sudden sleepiness during the day. Those details, alongside two weeks of honest entries, make it far easier to work out what is going on and what to try next.