Lee et al. 2025, Consumer wrist-worn sleep tracker accuracy vs polysomnography meta-analysis

Meta-analysis of 24 studies (798 participants) pooling accuracy data for Fitbit, Apple Watch, Garmin, WHOOP and other consumer wrist devices against polysomnography. Devices showed statistically significant deviations: total sleep time was on average 16.9 minutes lower than PSG (i.e. devices underestimated it), sleep efficiency was roughly 4.7% lower, and wake after sleep onset was 13.3 minutes higher. The authors concluded that wearables are useful for trend monitoring but that users and clinicians should interpret specific sleep parameters with caution, particularly staging. Moderate.