Consumer wearable devices to track health status and progress are commonly used and part of a growing trend of mobile health technology. However, how to interpret data from wearable devices, including step count, is at times unclear and there is a lack of guidance on how to use this data. For instance, patient-reported outcomes for heart failure are endorsed by the Food and Drug Administration for reporting symptoms, function and quality of life to support regulatory approval, but this does not include such data from wearable devices.
“Given the increasing availability of wearable technology to monitor physical activity, there is a pressing need to understand the clinical significance of changes in activity,” said Jessica Golbus, MD, MS, first author of the study and clinical instructor in the Division of Cardiovascular Diseases and the Department of Internal Medicine at the University of Michigan in Ann Arbor, Michigan. “[Our research showed] increased step counts were significantly associated with improvements in health status, suggesting that increases in step count over time as assessed by a wearable device may be clinically meaningful.”
The authors of the study sought to determine the relationship between activity measurement, specifically daily step count and floors climbed, and patient outcomes for people with heart failure. Researchers used data from the CHIEF-HF trial (Canagliflozin: Impact on Health Status, Quality of Life and Functional Status in Heart Failure), which was a randomized controlled trial that provided all participants with a Fitbit and asked them to complete serial Kansas City Cardiomyopathy Questionnaires (KCCQ) through a smartphone application.
The study cohort included 425 people with heart failure, including 44.5% female and 40.9% with heart failure with reduced ejection fraction. Researchers evaluated the relationship between daily step count and floors climbed and KCCQ total symptom and physical limitation scores at two weeks as well as their changes over 12 weeks. The KCCQ asks questions in four domains: physical limitation, symptom frequency, quality of life, and social limitation, and individual items are scored on a scale of zero to 100 with higher scores indicating better health. Changes in KCCQ scores of five points or more are considered clinically significant and have previously been shown to be associated with heart failure outcomes.
At two weeks, the mean KCCQ-physical limitation score was 55.7 and the KCCQ-total symptom score was 62.7. Physical limitation scores increased by four points on average through 12 weeks and total symptom scores increased by 2.5 points.
Researchers saw higher daily step counts with increased KCCQ scores for both physical limitation and total symptom scores. People with KCCQ-total symptom scores of zero-24 averaged 2,473 steps per day and those with scores of 75-100 averaged 5,351 steps per day. Participants climbed a mean of 2.7 floors per day, but daily floors climbed was not significantly different across different KCCQ score ranges.
Daily step count between 1,000 and 5,000 was significantly associated with symptoms and physical limitations based on KCCQ total symptom and physical limitation scores. Little association was seen once step counts reached higher than 5,000 steps per day. When comparing results to differing step counts, people who walked 1,000 steps per day had KCCQ-total symptom scores that were 3.11 points lower than people who walked 2,000 steps per day. And people who walked 3,000 steps per day had KCCQ-total symptom scores that were 2.89 points higher than those who walked 2,000 steps per day.
Changes in step count over time were also significantly associated with changes in KCCQ scores, suggesting that step count data from a wearable device may be leveraged to inform clinical care, or in the future, as clinical trial endpoints. The study found participants whose step counts increased by 2,000 steps per day saw a 5.2-point increase in their KCCQ-total symptom scores and a 5.33-point increase in their KCCQ-physical limitation scores when compared to participants with no change in step count.
People who saw a decline in their step count had numerical declines in their KCCQ-physical limitation score that were not statistically significant, when compared to participants with no change in step count.
“What does this mean at the end of the day? If providers see improvements in step counts, then that is a good thing and reflects that patients’ health status is likely improving,” Golbus said. “However, seeing a decrease in step counts does not necessarily mean the converse and would not necessarily require an intervention. It might mean following up with a patient though.”
In a related editorial comment, Mitchell Psotka, MD, PhD, section chief of heart failure and transplant at Inova Schar Heart and Vascular Institute in Falls Church, Virginia, discusses how actigraphy, or a way to quantify physical movement using step counts, is a promising but not completely realized tool for clinical and research purposes.
“These data are part of a large body of necessary and incremental work that will be required for actigraphy to attempt to achieve its potential as a patient-centered and efficient measure of functional status,” he said. “The authors have thankfully moved our understanding of actigraphy forward, though it is still the new kid on the block and will require substantial further testing and validation prior to widespread reliable clinical and research use.”
Limitations of the study include that the findings are from a randomized clinical trial and that commercially available wearable devices, like the ones used in the trial, may not be optimal for monitoring functional performance in patients with chronic diseases like heart failure because these devices have been shown to have poorer performance in patients with slower gait speeds. Also, patients were required to own a smartphone, which may bias study results toward those who are able to own smartphones. However, a 2021 study showed an estimated 85% of Americans across age, race and socioeconomic groups owned smartphones.
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