# What to trust on your wearable

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



## Takeaways

- Trust duration, distrust stages and composite scores.

- Use the device for accountability.



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

- Performance of seven consumer sleep-tracking devices compared with polysomnography (Chinoy ED, Cuellar JA, Huwa KE, et al., 2021)

- Wearable sleep technology in clinical and research settings (de Zambotti M, Cellini N, Goldstone A, Colrain IM, Baker FC, 2019)

- Orthosomnia: are some patients taking the quantified self too far? (Baron KG, Abbott S, Jao N, Manalo N, Mullen R, 2017)

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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.

SleepShred for iPhone: https://apps.apple.com/app/id6802040541