Whoop
Whoop 4.0 validation studies
2 peer-reviewed studies in the CircaTest corpus that validated this device against polysomnography or another reference standard.
Read CircaTest's Whoop 4.0 review →A performance validation of six commercial wrist-worn wearable sleep-tracking devices for sleep stage scoring compared to polysomnography
Schyvens et al., 2025 · Sleep Advances
Single most editorially important study in the CircaTest corpus. Six commercial wearables tested against PSG in a uniform protocol means the kappa values are directly comparable in a way most validation studies are not. Drives the head-to-head accuracy figures across CircaTest's comparison content. Limitations: tested previous-generation models (Series 8 not 10, Charge 5 not 6, original ScanWatch not 2) so the results are upper bounds for current models, not direct evidence.
A validation study of the WHOOP strap against polysomnography to assess sleep
Miller et al., 2020 · Journal of Sports Sciences
The only published independent PSG validation of a WHOOP device. CircaTest cites this as the canonical Whoop accuracy reference. The 64% four-stage agreement and the 8.2 ± 32.9 min TST overestimation are both editorially load-bearing.