WORN ON THE BODY

Muse S headband, £329.99, choose muse.com

CLAIM: ‘Using advanced EEG [electroencephelography] technology to respond to your mind, heart and breath, the Muse S is a comfy brain-sensing headband that helps you track how well you focus, sleep and recharge.’

It comes with an app full of guided meditations to use day or night. EEG uses sensors placed on the head to detect brainwaves.

VERDICT: This is the only product I tried that could provide accurate data on my sleep cycles, says Dr Santhi — because the sensors come into contact with areas of the head from which you can actually measure brainwaves.

‘This is most likely measuring activity only in the frontal area of the brain, and usually we measure multiple areas of the scalp as different stages of sleep are associated with brainwaves in different areas.

‘But they could argue you would get some information about REM and deep sleep from that in combination with an accelerometer [that senses movement].’

Dr O’Reilly adds: ‘They’ve included some meditation designed to help reduce stress and anxiety, which contribute to sleep disturbance. But it’s very hard to pick out what the contribution of the Muse band is to better sleep, over and above a sleep diary and meditation exercises.’

I used the Muse on the same night I slept next to the Google Nest (see box,

left) and it has me asleep for two hours and 40 minutes longer than the Nest (six hours and 20 minutes), which feels similar to the amount of time I was in bed. But it doesn’t pick up me waking at 4am, which I know happened because I looked at the clock. The graphs it provides show that I spent time in all the right stages of sleep in 90-minute cycles.

MY SCORE: The most likely to work, say the scientists — yet it misses me waking in the early hours. 6/10

Amazfit ZenBuds, £109, amazfit.com

CLAIM: These block noise and mask it by playing ‘soothing sounds’ to help you ‘fall asleep at night effortlessly’. The earbuds’ sensors ‘monitor your average resting heart rate, your sleep stages, sleeping positions and provide a sleep quality score’, which you check on an app.

VERDICT: ‘Environmental noise can disturb sleep, and dampening it with earbuds should be useful,’ says Dr Santhi.

Earplugs have helped my sleep in the past — yet I find these soft silicone buds distracting as they create a vacuum sensation in my ear. At 4am, I wake fully and have had enough — ripping them out of my ears.

The next day, they have tracked that well enough. But they failed to record anything for my heart rate, and insist I spent all four hours of my ‘sleep’ in light sleep — never entering deep or REM.

And despite the promise, they said nothing about my sleep position, though as Dr O’Reilly says ‘these trackers are not diagnostic’ and sleep position doesn’t really tell you much.

MY SCORE: Irritating and unreliable.

3/10

Whoop 3.0, from £288, whoop.com

CLAIM: This wristworn activity tracker focuses on ‘quality’ of sleep, promising to ‘track everything you’d need to know about your sleep . . . from sleep stages, cycles, disturbances and more’.

VERDICT: ‘Compared to the under-the-mattress sensors, a watch [or wrist-worn tracker] will always struggle that little bit more to define onset of sleep and wake, as there will be all sorts of “false alarms” throughout the day — if you are sitting in a movie theatre, unmoving for several hours in an evening, it could think you’re asleep, for example,’ says Dr Santhi.

Dr O’Reilly says he finds that wrist-worn trackers and other sleep trackers tend to overestimate sleeping time — as lying in bed staring at the ceiling while suffering terrible insomnia can register as sleep.

‘Your heart rate and movement levels can be very similar when trying to get to sleep to what they would be when you actually are asleep,’ he says.

For the first three nights, Whoop cannot over- or underestimate my sleep, because it won’t switch on or pair with my Bluetooth. On my fourth try, it does. The graphs look accurate and reassuring — six hours and five minutes of sleep, 23.9 per cent of it in deep sleep, which it tells me is ‘optimal for healthy adults’.

This was the one night I didn’t use any other trackers

as a point of comparison, but the experts agree the study supporting the device’s accuracy, published in the journal of clinical Sleep Medicine last year, is legitimate. MY SCORE: Points for a supporting study — and the good news that my sleep was ‘healthy’. 7/10

Garmin Venu Sq, £179.99, garmin.com

CLAIM: As well as tracking activity and exercise during the day, Garmin says this device provides ‘advanced sleep monitoring’, including a breakdown of your light, deep and ReM sleep stages as well as breathing data using a pulse oximeter. VERDICT: I was disappointed with this as a sleep tracker, which is a shame because as an activity tracker (its prime function) it’s great. I tested it on the same night as the Withings and Beurer devices, and it has me in light sleep at 11.37pm when I know for a fact I was in the bathroom. According to Garmin, I spend seven hours 42 mins asleep — including three hours eight minutes in ReM, compared with just 21 minutes on the Withings; in fact, the sleep stages and durations on all three trackers on the same night are wildly different.

Dr o’Reilly — who has a Garmin watch himself but uses it to track his golf performance rather than his bedtimes — is positive about the pulse oximeter function, which measures blood oxygen levels with lights on the back of the device via your wrist (although a fingertip reading would be better).

‘If you have sleep apnoea, your airway blocks for about ten seconds and in about half of people, their oxygen level will fall,’ says Dr o’Reilly. ‘This won’t measure it with sufficient accuracy but if it does show a drop in levels, it’s a helpful prompt to see your GP.’

MY SCORE: Not convinced by the sleep stages, but it does lots of other things well.

6/10