Accelerometer- versus questionnaire-based assessment of physical activity and their changes over time in patients with COPD
Received 14 December 2016
Accepted for publication 19 February 2017
Published 10 April 2017 Volume 2017:12 Pages 1113—1118
Checked for plagiarism Yes
Review by Single-blind
Peer reviewer comments 4
Editor who approved publication: Dr Richard Russell
Noriane A Sievi,1 Thomas Brack,2 Martin H Brutsche,3 Martin Frey,4 Sarosh Irani,5 Jörg D Leuppi,6 Robert Thurnheer,7 Malcolm Kohler,1,8 Christian F Clarenbach1
1Pulmonary Division, University Hospital of Zurich, Zurich, 2Pulmonary Division, Cantonal Hospital of Glarus, Glarus, 3Pulmonary Division, Cantonal Hospital of St Gallen, St Gallen, 4Pulmonary Division, Clinic Barmelweid, 5Pulmonary Division, Cantonal Hospital of Aarau, Aarau, 6University Clinic of Internal Medicine, Cantonal Hospital Baselland, 7Pulmonary Division, Cantonal Hospital of Münsterlingen, Münsterlingen, 8Zurich Centre for Integrative Human Physiology, University of Zurich, Zurich, Switzerland
Background and objective: Physical activity (PA) is an important outcome parameter in patients with COPD regarding hospitalizations and mortality. Both objective assessment by accelerometers and self-evaluation by questionnaires were used in studies investigating PA in COPD. Whether self-reported questionnaires can adequately reflect PA and its changes over time compared to objective assessments has not been thoroughly investigated in COPD. In this COPD cohort study, we evaluated whether PA measured by accelerometer and its annual changes can also be assessed by self-reported questionnaires.
Methods: In 178 COPD patients with at least two assessments of PA, the agreement between objectively measured and self-reported activity was analyzed by Bland–Altman plots. Daily PA was assessed by a triaxial activity monitor over 1 week and by the self-reported German PA questionnaire 50+.
Results: Comparison between the two methods of measurement revealed no convincing agreement with a mean difference and limits of agreement (±1.96 standard deviation [SD]) of time spent in at least moderate PA (>3 metabolic equivalent of task [MET]) of -77.6 (-340.3/185.2) min/day, indicating a self-reported overestimation of PA by the questionnaire. The mean difference and limits of agreement (±1.96SD) in the annual change of PA was 1.2 min/day (-208.2/282.6 min/day), showing also a poor agreement on an individual level.
Conclusion: Evaluation of objectively measured and self-reported PA and their annual changes revealed no agreement in patients with COPD. Therefore, the evaluated questionnaire seems not helpful for measurement of PA and its changes over time.
Keywords: activity monitor, activity questionnaire, airflow limitation, COPD
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