Validity and Acceptability of Wearable Devices for Monitoring Step-Count and Activity Minutes Among People With Multiple Sclerosis.
Grace Lavelle, Meriel Norris, Julie Flemming and 7 others
PMID 36188762WHAT IT FOUND
Commercially available activity monitors performed poorly for people with multiple sclerosis.
They gave inaccurate step counts and failed to measure activity time. Participants distrusted devices that seemed wrong, which reduced their motivation to use them. Do not rely on these specific consumer devices for clinical monitoring in this population.
Key findings
01All commercially available devices tested showed large percentage errors when compared to manually counted steps, with the Letscom having the largest error and the Yamax SW200 the smallest, though both were inaccurate.
02None of the devices provided valid estimates of time in physical activity, with the Garmin Vivofit 4 recording zero activity minutes for all participants and the Fitbit Alta recording zero for most, despite participants being active.
03Perceived accuracy was the most important factor for acceptability; participants rejected devices they believed were inaccurate, such as those recording steps during sitting or driving, which caused frustration and distrust.
STILL TO COME
How it was doneWhat they foundWhat it means for PTsWhat it means for OTs
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What it does not show
The study was conducted in a controlled environment for the validity phase, which may not fully replicate the variability of free-living conditions, although activities were chosen to mimic daily life. The sample size was small (19 participants), limiting the generalizability of the findings. The participants were ambulatory adults with MS; findings do not apply to wheelchair users or those with more severe mobility impairments. One of the devices tested (Fitbit Zip) has since been discontinued, which may limit the direct applicability of specific device recommendations to current market offerings. Perceived accuracy was assessed qualitatively and may not align perfectly with objective validity metrics, though both pointed to poor device performance.
Declared interests
The authors declared no conflicts of interest. The study was funded by the RCSI University of Medicine and Health Sciences STAR Programme and Brunel University London.
The easy way to misread this
Do not assume that a device being popular or 'smart' makes it accurate for people with multiple sclerosis. This study shows that even devices with good agreement in general populations performed poorly here, often recording steps during sitting or driving. Trusting these numbers could lead to incorrect clinical conclusions about a patient's activity level.