Nature and science of sleepMar 7, 2023

Comparing Fitbit Inspire 2 Sleep Tracking to Standard Sleep Tests in Adults, Including Adjustment for Use

Circadian Biology Weekly Brief ↗PubMed ↗DOI ↗OA ↗

Updated Apr 3, 2026

Abstract

Fitbit Inspire 2™ (FBI2) showed high (93.9%) but low (13.1%) in tracking sleep compared to (PSG).

Significant differences were observed between FBI2 and PSG in total sleep time (TST), deep sleep, and rapid eye movement (REM) sleep.
FBI2 overestimated TST, deep sleep, and REM, while underestimating light sleep, although these differences were not statistically significant.
Accuracy for overall sleep measurement using FBI2 was recorded at 76%.
Specificity and sensitivity for light sleep were 62.3% and 54.3%, respectively; for deep sleep, they were 50.1% and 84.8%; and for REM sleep, 59.1% and 86.4%.

Simplified

PURPOSE: The commercialization of sleep activity tracking devices has made it possible to manage sleep quality at home. However, it is necessary to verify the reliability and accuracy of wearable devices through comparison with (PSG), which is the standard for tracking sleep activity. This study aimed to monitor overall sleep activity using Fitbit Inspire 2™ (FBI2) and to evaluate its performance and effectiveness through PSG under the same conditions.

PATIENTS AND METHODS: We compared the FBI2 and PSG data of nine participants (four male and five female participants; average age, 39 years) without severe sleeping problems. The participants wore FBI2 continuously for 14 days, considering the period of adaptation to the device. FBI2 and PSG sleep data were compared using paired-tests, Bland-Altman plots, and epoch-by-epoch analysis for 18 samples by pooling data from two replicates. t

RESULTS: The average values for each sleep stage obtained from FBI2 and PSG showed significant differences in the total sleep time (TST), deep sleep, and rapid eye motion (REM). In the Bland-Altman analysis, TST (= 0.02), deep sleep (= 0.05), and REM (= 0.03) were significantly overstated in FBI2 compared to PSG. In addition, time in bed, sleep efficiency, and wake after sleep onset were overestimated, while light sleep was underestimated. However, these differences were not statistically significant. FBI2 showed a high (93.9%) and low (13.1%), with an accuracy of 76%. The sensitivity and specificity of each sleep stage was 54.3% and 62.3%, respectively, for light sleep, 84.8% and 50.1%, respectively, for deep sleep, and 86.4% and 59.1%, respectively for REM sleep. P P P

CONCLUSION: The use of FBI2 as an objective tool for measuring sleep in daily life can be considered appropriate. However, further research is warranted on its application in participants with sleep-wake problems.

Key numbers

17.91 minutes

Overestimation of Total Sleep Time

Difference in total sleep time between FBI2 and .

93.9%

Total Sleep

High indicates effective detection of sleep periods.

13.1%

Total Sleep

Low reflects challenges in accurately detecting wakefulness.

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Comparing Fitbit Inspire 2 Sleep Tracking to Standard Sleep Tests in Adults, Including Adjustment for Use

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