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After the week · Lesson 10 of 11

Sleep Trackers and Sleep Aids: What They Can and Can't Do

See how sleep trackers guess, why weekly patterns beat nightly scores, and why you should ask a pharmacist or doctor before any sleep aid.

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Cover picture for lesson 10: Sleep Trackers and Sleep Aids: What They Can and Can't DoVideo coming soon
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Sleep trackers and sleep aids are everywhere. In this lesson you see what they can tell you, and what they cannot do. This is general information, not medical advice, and it names no products.

How trackers guess

A watch or a ring does not measure sleep directly. It guesses from your movement and your heart rate. So if you lie awake but stay still, it may count that as sleep.

A watch with a line graph and two labels, Movement and Heart rate. On the right, a person lying awake in bed, labelled Awake, but very still, and a watch showing Asleep with a red question mark and the label Counted as sleep?(opens the full-size picture)
A tracker sees stillness and heart rate, not whether you are awake.

How accurate they are

In one study of seven devices, they caught at least 93 percent of sleep, but only 18 to 54 percent of the time people were awake. Most also missed a lot of deep and dream sleep, calling it light sleep. That is one lab study, so take the exact figures lightly. The message is that trackers are good at saying “asleep” and weak at saying “awake”.

A tall green bar labelled At least 93% for sleep caught and a shorter red bar labelled 18 to 54% for awake time caught, with the note 7 devices, one lab study. Two labels on the right say Deep and dream sleep missed and Often logged as light sleep.(opens the full-size picture)
Sleep caught: at least 93%. Awake time caught: 18 to 54%.

Patterns, not scores

So use a tracker for patterns, not scores. Look at your weekly average bedtime and wake time. Skip the nightly split of light, deep and dream sleep. And if checking your score makes you anxious, judge your night by how you feel during the day.

Seven navy bars for Monday to Sunday, labelled Weekly pattern and Bedtime to wake time, each night. On the right a card called Last night with a deep sleep time and Light, Deep and Dream bars, crossed in red. A yellow label says Anxious about the score? Judge by your day.(opens the full-size picture)
Keep the weekly pattern. Skip the one-night score.

Magnesium and melatonin

What about supplements? Magnesium is not a proven sleep aid. The studies are few and small, and reviews rate the evidence as low.

A supplement bottle labelled Magnesium beside a scale tipping toward the heavier side, under the heading Evidence: low. Labels say Few and small studies and Not a proven sleep aid, the second crossed in red.(opens the full-size picture)
Few and small studies, and low-rated evidence.

US and European sleep guidelines do not recommend melatonin for long-term insomnia. The rules differ by country. In the UK, for example, it is prescription-only.

A supplement bottle labelled Melatonin. Beside it, under the heading US and European guidelines, a red label Not recommended for long-term insomnia, a yellow label Rules differ by country, and a UK card with a pill packet and the words Prescription only.(opens the full-size picture)
Not recommended for long-term insomnia, and the rules differ by country.

Ask first

Over-the-counter sleep aids cannot cure insomnia, and the NHS says to use them for no more than one to two weeks. Before you take any sleep aid, ask a pharmacist or a doctor, especially if you are pregnant, take other medicines, or have a health condition.

A pill packet beside a calendar that says 1 to 2 weeks, with the labels Cannot cure insomnia and 1 to 2 weeks at most. On the right, a smiling pharmacist with a speech bubble Ask first and three labels: Pregnant, Other medicines and Health condition.(opens the full-size picture)
Ask a pharmacist or doctor first, and never for more than 1 to 2 weeks.

Rules differ around the world

Which sleep aids you can buy, and which need a prescription, depends on your country. A local pharmacist can tell you what applies where you live.

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Read the full lesson script

Sleep trackers and sleep aids are everywhere. In this lesson, you'll see what they can tell you, and what they can't do.

A watch or a ring doesn't measure sleep directly. It guesses from your movement and your heart rate. So if you lie awake but still, it may count that as sleep.

In one study of seven devices, they caught at least 93 percent of sleep, but only 18 to 54 percent of the time people were awake. Most also missed a lot of deep and dream sleep, calling it light sleep.

So use a tracker for patterns, not scores. Look at your weekly average bedtime and wake time. Skip the nightly split of light, deep and dream sleep. And if checking your score makes you anxious, judge your night by how you feel during the day.

What about supplements? Magnesium is not a proven sleep aid. The studies are few and small, and reviews rate the evidence as low.

US and European sleep guidelines don't recommend melatonin for long-term insomnia. The rules differ by country. In the UK, for example, it's prescription-only.

Over-the-counter sleep aids can't cure insomnia, and the NHS says to use them for no more than one to two weeks. Before you take any sleep aid, ask a pharmacist or a doctor, especially if you're pregnant, take other medicines, or have a health condition.

So remember: trackers guess, so use them for weekly patterns, not nightly scores. Magnesium and melatonin are not proven fixes for poor sleep. And ask a pharmacist or a doctor before any sleep aid. Before the next lesson, if you use a tracker, look only at this week's average bedtime and wake time. In the last lesson, you'll learn when to see a doctor, and you'll put your plan together.