“At the risk of making a pun, this has got legs,” was one response to the exciting new research that Valerie J Block, PT, DPTSc, presented at a recent (2018) meeting of the American Academy of Neurology. Block, a physical therapist, has been studying the use of wrist-worn accelerometry (step counters) to track daily mobility in MS patients. She is one of a new generation of researchers trying to close the gap between the potential and actual use of today’s wearable technology in medicine.
Wearable technology is well seated in the public mainstream; people are tracking their steps, their sleep, their blood pressure, their location and much more. While this information can be anecdotally very interesting, it’s hard to say whether it is accurate and reliable enough to be used as part of an evidence-based medical approach. But that is starting to change, and Block’s work is a great example of this.
Multiple Sclerosis can have a devastating impact on ambulation. This is, of course, well known, and it’s why most of the functional assessment tools used in the clinic on MS patients contain some measure of ambulation. These tools include the Expanded Disability Status Scale (EDSS), the Timed 25-Foot Walk (T25-FW) test, the Two-Minute Walk Test (2MWT), and the Timed Up and Go (TUG) test. Function is also assessed using Patient Reported Outcomes (PROs) which may include information related to walking.
The problem says Block is that PROs aren’t always reliable and the assessments done in clinic are just “snapshots of function. They don’t really tell us how people are doing in their everyday lives.”
The EDSS, mentioned above, offers a good case in point. The EDSS rates functional mobility on a scale of one (no disability) to ten (death). An EDSS score of six means the individual requires a walking aid such as a cane. But, as Block points out, “We don’t know whether this person can walk many miles a day with their cane, or whether they’re essentially home bound because of the need to use this cane.”
In other words, clinicians and researchers need more nuanced ways to capture patients’ function as they are living their lives between visits to their neurologist. The latest generation of wearable step trackers may provide a solution.
Are Step Trackers Viable?
As part of her doctoral thesis and continuing into her postdoc work at University of California at San Francisco (UCSF), Block has been looking at the best ways to measure daily functional ability in neurological patients. In 2016 she was first author of a systematic review of a variety of neurological diseases (MS, stroke, PD, and ataxia) and remote physical activity monitoring. For MS alone, she and her coauthors found almost 140 studies that met their inclusion criteria. They concluded, “In MS, decreased ambulatory activity assessed via remote monitoring is associated with greater disability and lower quality of life.”
This led her to design another study looking more closely at the remote monitoring of ambulation in MS patients. Nearly a hundred men and women, aged 24–74, with either progressive or relapsing MS were enrolled. The cohort was assessed at baseline and one year using the clinical measures mentioned above, like the EDSS, and intermittently using PROs.
Each patient was outfitted with a wrist-worn accelerometer to measure daily step count. The device Block and her team chose was the Fitbit Flex. “Actually the Fitbit One, which is clipped onto the waist, seems to be the most accurate measure,” said Block after her talk at AAN. “But for a study that’s going to be a year long and the amount of times that Fitbit’s going to end up in the wash,” it just wasn’t practical or economical.
The cohort was followed for a year with the aim of answering two primary questions:
- Is it feasible for these MS patients to use the Fitbit Flex for a year?
- Will the data collected by the Fitbit Flex correlate with clinic-based and patient reported outcomes over the year?
The short answer to both those questions turned out to be, yes. Study retention was high. Block enrolled 95 patients into her study and 79 made it to the end of the year—that’s a retention rate of 83 percent. Further, there was a clear correlation between step count and the more traditional measures of disability like the EDSS; as step count went down, disability went up.
In other words, the Fitbit Flex was both feasible for MS patients to use, and the data it returned was in line with other verified tests of function.
But the data revealed much more.
The next question is whether a wrist-worn accelerometer can do a BETTER job than established tools. Stay tuned for that in Part Two.