SleepShred
Get the app

What to trust on your wearable

Total sleep time: yes. Deep/REM and 'sleep scores': no.

Wearables are awesome for awareness and accountability, and pretty good for total sleep time. They are really, really bad at predicting deep and REM sleep, and aggregate 'sleep quality' or 'readiness' scores won't be directionally reliable. Head-to-head against polysomnography, seven consumer devices tracked total sleep reasonably but misclassified stages.

That's why SleepShred shows total sleep time large, shows stage minutes small with a low-confidence caveat, and never computes an aggregate sleep score.

Sources · 3

Performance of seven consumer sleep-tracking devices compared with polysomnographyChinoy ED, Cuellar JA, Huwa KE, et al. · 2021Consumer devices estimated total sleep well but were poor at sleep stages — trust duration, not deep/REM.Wearable sleep technology in clinical and research settingsde Zambotti M, Cellini N, Goldstone A, Colrain IM, Baker FC · 2019Review of what wearables can and cannot measure; stage classification and 'sleep scores' lack validation.OrthosomniaBaron KG, Abbott S, Jao N, Manalo N, Mullen R · 2017Case series of people whose fixation on tracker data worsened their sleep — Galpin's health-anxiety warning has a name.

Related topics

Wearables & tracking

Frequently asked questions

What to trust on your wearable?

Total sleep time: yes. Deep/REM and 'sleep scores': no.

Is SleepShred free?

No. SleepShred Pro is $4.99 per month or $29.99 per year, with no free trial and no ads. Everything stays on your iPhone.

Track it, don't guess it

SleepShred turns this research into a 20-second daily habit: log your night, see which of your own behaviours move your sleep, and screen for the disorders nobody diagnoses.

Get SleepShred for iPhone

Educational summary of published research, not medical advice. Screening scores are not diagnoses. If a score is elevated or you feel unwell, talk to a clinician.