Measuring activity in COPD and other less active populations


Measuring free-living physical activity in COPD patients

This article presents a review of the research literature to identify the methodology used and outcome measures derived in the use of accelerometers to measure free-living activity in patients with COPD. 

In many clinical trials, improvements in physical activity and mobility are important secondary outcomes. These are often estimated using in-clinic controlled assessments of exercise capacity such as treadmill tests and corridor circuits including the six minute walking test.  Many drug treatments that improve symptoms, may also enable increased activity and mobility with corresponding improvements in quality of life. These improvements may be better examined by measuring free-living activity, and in less active patient populations this may include measuring increased participation in discretionary non-essential tasks requiring levels of physical activity. While activity monitors have been used in clinical trials, some researchers consider a number of perceived barriers limiting their use. These include:

  1. Regulatory acceptance of the validity of devices and the data management assumptions made
  2. Scientific understanding of the data recorded and how to derive meaningful summary outcome measures; and
  3. A lack of standards for implementing activity data collection in clinical trial protocols. 

Working with Dr. David Rowe (School of Psychological Sciences and Health, University of Strathclyde, Glasgow, UK) we have developed a set of recommended standards for activity measurement in patients with COPD that also apply to other less active patient populations.

Implementation standards
In our review we identified a huge variation in methodology practices across the 76 COPD studies examined. Based on this, and other key scientific work, we derived a set of recommended implementation standards that are supported by solid scientific rationale to study activity changes in COPD and other less active patient populations. These include:

  • Activity monitor type, characteristics and placement location
  • Wear interval and valid day definition
  • Definition of a non-wear episode
  • Missing data methodology.

Derived health outcome measures
We have defined a set of pertinent outcome measures important in characterizing activity in less active patients, that may be sensitive to detecting treatment-related changes. These include measures of sedentary behaviour, light to moderate activity and overall activity. We grade our recommendations based on the strength of research evidence that support them, and indicate where additional research would be valuable.  The outcome measures we recommend are described in full in our journal article

The aim of this work is to attempt to take a positive step forward in defining acceptable standards for the use of activity monitors in regulatory clinical trials and is aimed at eliminating the perceived barriers to wide scale adoption.

Read full details of our review and recommendations in the published article in the Contemporary Clinical Trials

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  • Medical Device