UNDER THE MATTRESS
Withings Sleep Analyzer, £99.96, withings.com
CLAIM: Slip this sensor under your mattress to provide ‘clinically validated, sleep-lab results at home’ sent to an app.
It promises to track sleep duration, onset and waking; sleep apnoea (where breathing ceases for short periods) and its severity; sleep cycle phases, heart rate, snoring and provide a ‘sleep score’ using a pressure sensor and audio.
VERDICT: I feel like the princess and the pea. But I don’t notice a single lump or bump. If I can’t feel it through the mattress, though, can it really sense my heart rate and breathing?
‘Many of these trackers are very sensitive, and can sense movement and the vibration of the heart, and record the sound of breathing and snoring [a sign of sleep apnoea] quite well,’ says Dr O’Reilly. ‘This one does appear to be effective at sensing sleep apnoea, as the study that’s been done on it is by a respected researcher.’
My data the next morning looks believable — I slept for six hours and 34 minutes, between 11.50pm and 6.31am, with a seven-minute interruption from 6.18am to 6.25am. My average heart rate was 53 beats per minute, my level of sleep apnoea was ‘normal to mild’. However, my sleep cycle data says my sleep was ‘bad’, with a big red circle — I spent no time in deep sleep and just 5 per cent (21 minutes) in REM.
Dr O’Reilly says: ‘The problem is that your tracker hasn’t been able to distinguish between deep and light sleep because the heart rate in both is very similar and it’s only using that and movement to judge, not brain electrodes as in a sleep lab. And it’s only judging REM based on a lack of movement and an increase in heart rate, which is a little bit woolly at best, rather crude at worst.’
This is a problem faced by all the trackers here which claim to track sleep stages, apart from Muse.
If I woke up having had no deep sleep and a sliver of REM, ‘you wouldn’t need a tracker to tell you, you’d feel dreadful’, adds Dr Santhi, but I woke feeling refreshed.
MY SCORE: Good for sleep apnoea detection, bad for sleep cycles.
5/10
Beurer SE 80 SleepExpert sleep sensor, £79.99, chemist-4-u.com
CLAIM: A disc-shaped sensor the size of a side plate, which the maker says can ‘precisely’ record heart rate, respira
tory rate and movement; provide sleep phase analysis; detect interruptions to breathing, as well as having a ‘moon phase display’ and a function to help you wake up in the ‘right’ sleep phase.
VERDICT: I’m suspicious of the science behind the ‘moon phase display’ but Dr Santhi says some research has shown that the phases of the moon might affect our sleep — ‘these are emerging lines of research that need further enquiry.’
The promise to wake you in the right sleep phase is questionable, as the right phase to wake from is light sleep, but Dr O’Reilly says these trackers are generally poor at distinguishing between light and deep sleep.
I used this and the Withings tracker on the same night and the next morning the reports on the time I fell asleep and my heart rate were similar but, according to Beurer, I got more REM and deep sleep (17 and 16 per cent respectively). ‘That seems a bit more like a normal rate,’ says Dr O’Reilly.
On the downside, it seems I spent only five hours and six minutes asleep, rising at 5.44am — which wasn’t the case, although I do recall a brief period of wakefulness when I may have rolled out of the sensor’s range.
MY SCORE: Easy to use and relatively accurate.
7/10