Research
Mixed
Consumer wearable sleep trackers generally overestimate total sleep time and sleep efficiency while underestimating wake after sleep onset compared to polysomnography, with high sensitivity but low specificity for wake detection.
Use wearable sleep trackers to observe long-term trends in your sleep habits, not to diagnose sleep disorders. Expect them to overestimate how much you slept and underestimate how much you were awake. For clinical concerns, rely on professional sleep studies (PSG).
GoodQualifiesHIGH confidence
The majority of studies report high sensitivity (ability to detect true sleep) and accuracy (overall ability to detect true wake and sleep), actigraphy is inherently impaired in detecting true wake (specificity) as it is unable to identify motionless wake... Fitbit... overestimated PSG TST (by 41 min) and SE (by 7.0%), and underestimated SOL (by 13.5 min) and WASO (by 27.1 min)
Why this rating
Based on a comprehensive review of multiple validation studies against gold-standard PSG.
Source
Wearable Sleep Technology in Clinical and Research Settings
Massimiliano de Zambotti et al. · Medicine & Science in Sports & Exercise · 2019
DOI 10.1249/mss.0000000000001947
narrative_reviewCited 511×
Read the paper DOI resolved against Crossref · corpus check 2026-06-10
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