What seven days of sleep notes can tell you

Why clinicians use sleep diaries

When someone tells a doctor they are sleeping badly, the doctor needs more than a general impression, and a diary is the standard way to get it. The NHLBI suggests keeping one for one to two weeks before a visit about sleep.[3] The American Academy of Sleep Medicine’s guideline on chronic insomnia in adults recommends collecting diary data both before and during treatment.[21]

Sleep researchers have also agreed a standard format, the Consensus Sleep Diary. It was developed by insomnia experts with input from good sleepers and from people with insomnia or sleep apnea.[20] Its authors call it a living document that still needs testing and validation,[20] which is a fair description of sleep diaries in general: widely used, genuinely useful, and imperfect.

The word the researchers use is prospective.[20] A diary is filled in day by day as the week happens, not pieced together from memory at the end of it. That is the whole point of it, and it is why the habit matters more than the format.

What to record

Keep the core short enough that you will actually do it every day:

• roughly when you went to bed, and roughly when you got up
• about how long it took to fall asleep
• how many times you remember waking, roughly when, and for how long
• how rested you felt on waking, in a word or two

Then add a few lines about the day before, because that is where most of the useful context lives. Each of these is on the list for a reason:

• The time of your last caffeine. In a small trial, a large dose disrupted sleep even when it was taken six hours before bed.[13]
• Any alcohol, and when. In healthy volunteers it tends to settle the first half of the night and disrupt the second.[15]
• When you first saw daylight, and when screens went off. Light reaching the eyes is the main signal that keeps the body clock aligned with the day.[17]
• Anything stressful, and whether you were worrying about sleep itself at bedtime. Both are listed risk factors for insomnia.[1]
• For women in midlife, hot flashes or night sweats, which are linked to night waking around menopause.[18]
• Anything a partner noticed, such as loud snoring, gasping or pauses in breathing, which can be signs of sleep apnea.[19]

Leave a line at the bottom for anything else: a late meal, a hard workout, a sick child, a different bed. You won’t know in advance which detail turns out to matter.

Paper or phone is your choice, with one caution. A phone by the bed brings its own light, and in a lab study, evening reading on a light-emitting screen meant taking longer to fall asleep and a later body clock than reading a printed book.[16] That is one argument for a paper diary, or for filling in an app only once you are up.

Fill it in from memory, in the morning

Write the night down within an hour or so of getting up, while it is still fresh, and be content with estimates. “Around 3, maybe twenty minutes” is a perfectly good entry. So is “not sure”.

What you should not do is check the clock during the night so that the diary is more accurate. Watching the clock and worrying about how much sleep you are getting are themselves listed as risk factors for insomnia.[1] A diary that makes you more anxious about sleep is working against you. If you look at the time out of habit, write down that you looked, not what it said.

Fill in the daytime section before bed or the next morning, whichever you are more likely to keep up. Missing a day is fine. Guessing a missed day a week later is less useful than leaving it blank, since a blank is honest and a guess is just a guess.

Reading a week without over-reading it

At the end of the week, look across all the days before you look at any one of them. A few questions help:

• Did the rough nights cluster after particular evenings: late caffeine, a drink, a late screen?
• Did your bedtime and wake time move around a lot, especially between weekdays and the weekend?
• Were the wakings at a similar time each night, or scattered?
• Did the days match the nights, or were some poor nights followed by perfectly ordinary days?

Then apply some caution. Seven days is a small sample, which is one reason the NHLBI suggests one to two weeks.[3] Brief arousals are a normal part of sleep and become more frequent with age,[6] and time spent awake after first falling asleep also tends to rise as we get older.[5] So a night with two remembered wakings is not, on its own, a sign of anything.

Treat any pattern you spot as a lead, not a conclusion. If the worst nights all follow late coffee, that is worth testing. Change one thing at a time and keep the diary going for another week, so you can see whether the pattern actually moves. Changing three things at once will tell you very little, even if you feel better.

Here is how that might look in practice. Say your notes show three rough nights, and all three followed a drink with dinner. A reasonable next step is a week without the drink at dinner, still recording everything else. If the rough nights fade, you have something worth mentioning to a clinician. If they carry on regardless, you have learned something too, and you have crossed one possibility off the list.

What a diary can’t show

A diary is self-report. It records what you noticed and remembered, which is valuable and also partial. Brief arousals measured in a sleep lab are not the same thing as awakenings you remember,[6] so many of the night’s small events will never make it onto the page.

It also can’t see what happens while you are soundly asleep. Breathing that stops and starts, a sign of sleep apnea, is often noticed by someone else, and diagnosing sleep apnea needs a sleep study.[19] A sleep study can look for problems like this that no diary can pick up.[3]

And a diary says nothing about hormones. Cortisol disorders, for example, are diagnosed with a medical history, an exam and lab tests, usually more than one.[24] Seven pages of notes can’t stand in for that, and they shouldn’t be asked to. What they can do is describe your sleep and your days as you actually live them, which is something no lab test records.

Bringing it to a clinician

The NHLBI suggests talking to a doctor if poor sleep is affecting your daily activities.[3] You don’t need a finished diary to ask for help. If you notice loud snoring, gasping or strong daytime sleepiness,[19] don’t wait for the week to end.

If you have kept one, bring the pages along with a short summary on top:

• your usual bedtime and wake time, and how much they varied
• how many nights out of seven felt poor
• any pattern you think you saw, and how sure you are about it
• anything you changed during the week, and what happened

Some questions worth asking:

• Does anything here suggest I should have a sleep study?
• Could a health condition or a medication I take be involved?
• What would you like me to track next, and for how long?