In recent years, wearable technology has gained traction in the realm of digital health, particularly for monitoring sedentary behavior among patients with cardiovascular conditions. This validation study, published in JMIR Cardio, assesses the accuracy of a consumer-grade wrist-worn activity tracker, specifically the Fitbit Inspire 3, in comparison to a research-grade waist-worn accelerometer, the ActiveStyle Pro HJA-750C.
The study involved 51 outpatients diagnosed with heart failure or ischemic heart disease, with a mean age of 78.4 years. Each participant wore both devices simultaneously for a period of seven days, during which their sedentary time was recorded within a standardized 12-hour window from 9 AM to 9 PM.
Results indicated that the mean sedentary time recorded by the waist-worn accelerometer was 497.9 minutes, while the Fitbit reported a higher average of 559.9 minutes. The correlation between the two devices was strong, with a Pearson correlation coefficient of 0.905. However, the Fitbit exhibited a fixed bias, overestimating sedentary time by approximately 62 minutes.
To assess the agreement between the two devices, various statistical methods were employed, including Bland-Altman analysis and Lin concordance correlation coefficient (CCC). The uncorrected concordance was moderate (CCC=0.71), but after applying a constant bias correction, the concordance improved significantly to approximately 0.90.
Despite the promising results, the study highlighted that the wide limits of agreement between the two devices could limit the precision of individual-level assessments. The authors emphasized that while the calibrated use of consumer wearables could be beneficial for monitoring in ambulatory cardiac care, the population-specific correction factor necessitates further validation before being applied in different settings.
What this study does not show
This study does not demonstrate the effectiveness of the wrist-worn tracker in improving health outcomes for patients with cardiovascular disease.
Evidence scorecard
- Analytic validity: Established
- Clinical validity: Established
- Clinical utility: Not established
The evidence is based on a validation study involving human participants.