Fitbit Sense 2 in hospitalized general medicine patients: A pilot study assessing feasibility and validity of specific measures.

INTRODUCTION Reduced sleep and mobility in acute care contribute to post-hospital syndrome, yet they are rarely monitored in this setting. Wearable devices like Fitbits can passively track these factors, but their validity in hospitalized patients remains uncertain.

Objectives

To assess the validity of Fitbit Sense 2-derived heart rate, step counts, sleep and oxygen saturation in hospitalized internal medicine patients compared with validated reference devices; the secondary aim was to examine patient perceptions of continuous wearable device monitoring.

Methods

A prospective cohort pilot study was conducted over 24 h among internal medicine patients at a large academic hospital (Toronto, Canada). Fitbit data were compared against Nox T3s (sleep quality, heart rate, oxygen saturation) and StepWatch (step count) using Bland-Altman analysis and intraclass correlation coefficient (ICC). Sensitivity and positive predictive value (PPV) were calculated to detect sedentary, light and moderate activity (<40, 40-400, >400 steps/hr). Patient perceptions were collected via questionnaires.

Results

Of 33 patients enrolled (mean age 52.6 years), Fitbit data completeness varied: heart rate and step count 100 %, total sleep time and sleep efficiency 91 %, REM 56 %, oxygen saturation 41 %. Heart rate tracked closely with the reference (-0.3 bpm, ICC 0.998). Step counts were overestimated (bias + 29.4 steps/hr, ICC 0.64) but showed promise for sedentary detection (sensitivity 75 %; PPV 91 %). Total sleep time (bias -0.1 hrs; ICC 0.65) and sleep efficiency (bias -2.0 %; ICC 0.69) showed moderate agreement with wide limits of agreement (±4 hrs and ± 36 %, respectively). REM was overestimated (+29.4 min; ICC 0.41). Oxygen saturation showed modest agreement (bias + 1.7 %; ICC 0.47). Device usability was rated positively.

Conclusion

In hospitalized internal medicine patients, the validity of wearables varied considerably by measure: heart rate and sedentary detection appeared promising, whereas absolute step count, sleep and oxygen saturation showed greater variability and higher rates of missing data. Patient perceptions of wearables were highly positive. These findings inform the design of larger validation studies. TRIAL IDENTIFIER NCT07229833.