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Fitbit-Type Devices Useful for Coaching but Not Clinically Accurate in COPD


Activity trackers, like Fitbits, are not accurate enough for clinical use but may be helpful for coaching in conditions like COPD, a study says.

Consumer-based activity trackers are inaccurate as a tool to measure physical activity in patients with chronic obstructive pulmonary disease (COPD) but can be helpful as a coaching tool, according to a study published in PLoS One.

As more patients with COPD receive recommendations to increase physical activity as a nonpharmacological intervention, patients may want to use consumer-based trackers to monitor their daily activity as they are easy to use, provide real-time feedback, and can provide activity-related information including step counts, energy expenditure, intensity of activities, and heart rate. But the accuracy of these consumer devices for clinical use or as a coaching device is unknown. Investigators said the study is the first to evaluate the accuracy of consumer-based activity trackers as a coaching tool in patients with COPD.

This study evaluated the use of the hip-worn Fitbit Zip and the wrist-worn Fitbit Alta against the Dynaport Movemonitor, a medically validated activity monitor developed specifically for use in COPD.

The final analysis included 28 patients with COPD and 14 matched healthy controls, who wore all 3 devices simultaneously for 14 consecutive days. The Dynaport, worn on a belt across the lower back, served as the reference.

Researchers compared the mean daily step count as measured by the Fitbits with the Dynaport in COPD and healthy controls separately by use of a paired t-test. They tested the hypothesis that the accuracy of the trackers relates to walking speed by pooling the groups and using univariate linear analyses to examine the differences among the devices. In addition, they probed the agreement of mean step count with Bland-Altman plots.

In both patients with COPD and healthy subjects, the hip and wrist activity trackers were able to detect patterns of more and less active days similarly to the Dynaport, with the added benefit of giving real-time feedback to patients.

However, for patients with COPD, the hip-based Fitbit significantly underestimated the daily step count compared with the Dynaport by 23% (mean 1112 [–872]; P < .0001).

Compared with healthy participants, the Bland-Altman analysis showed that the hip tracker had a lower mean bias for physical activity in patients with COPD (95% CI, –1055 steps vs –391 steps)

Compared with the Dynaport, the mean daily step count measured by the wrist activity tracker was not significantly different for patients with COPD (mean 374 [1257] steps per day, P = .13).

Investigators found that the inaccuracy of the consumer-based trackers was related to movement intensity, with hip trackers having a tendency to lack accuracy in those who are less active and wrist trackers lacking accuracy in more active populations.

Patients with COPD are often less active than healthy subjects, having overall a smaller spectrum of daily life activities and are often slow walkers, they noted.


Blondeel A, Demeyer H, Janssens W, Troosters T. Accuracy of consumer-based activity trackers as measuring tool and coaching device in patients with COPD and healthy controls. PLoS One. Published online August 4, 2020. doi: 10.1371/journal.pone.0236676

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