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. 2013 Apr 4;8(4):e60400.
doi: 10.1371/journal.pone.0060400. Print 2013.

Daily step count predicts acute exacerbations in a US cohort with COPD

Marilyn L Moy  1 , Merilee Teylan, Nicole A Weston, David R Gagnon, Eric Garshick
Affiliations

Daily step count predicts acute exacerbations in a US cohort with COPD

Marilyn L Moy et al. PLoS One. .

Abstract

Background: COPD is characterized by variability in exercise capacity and physical activity (PA), and acute exacerbations (AEs). Little is known about the relationship between daily step count, a direct measure of PA, and the risk of AEs, including hospitalizations.

Methods: In an observational cohort study of 169 persons with COPD, we directly assessed PA with the StepWatch Activity Monitor, an ankle-worn accelerometer that measures daily step count. We also assessed exercise capacity with the 6-minute walk test (6MWT) and patient-reported PA with the St. George's Respiratory Questionnaire Activity Score (SGRQ-AS). AEs and COPD-related hospitalizations were assessed and validated prospectively over a median of 16 months.

Results: Mean daily step count was 5804±3141 steps. Over 209 person-years of observation, there were 263 AEs (incidence rate 1.3±1.6 per person-year) and 116 COPD-related hospitalizations (incidence rate 0.56±1.09 per person-year). Adjusting for FEV1 % predicted and prednisone use for AE in previous year, for each 1000 fewer steps per day walked at baseline, there was an increased rate of AEs (rate ratio 1.07; 95%CI = 1.003-1.15) and COPD-related hospitalizations (rate ratio 1.24; 95%CI = 1.08-1.42). There was a significant linear trend of decreasing daily step count by quartiles and increasing rate ratios for AEs (P = 0.008) and COPD-related hospitalizations (P = 0.003). Each 30-meter decrease in 6MWT distance was associated with an increased rate ratio of 1.07 (95%CI = 1.01-1.14) for AEs and 1.18 (95%CI = 1.07-1.30) for COPD-related hospitalizations. Worsening of SGRQ-AS by 4 points was associated with an increased rate ratio of 1.05 (95%CI = 1.01-1.09) for AEs and 1.10 (95%CI = 1.02-1.17) for COPD-related hospitalizations.

Conclusions: Lower daily step count, lower 6MWT distance, and worse SGRQ-AS predict future AEs and COPD-related hospitalizations, independent of pulmonary function and previous AE history. These results support the importance of assessing PA in patients with COPD, and provide the rationale to promote PA as part of exacerbation-prevention strategies.

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Conflict of interest statement

Competing Interests: The authors have declared that no competing interests exist.

Figures

Figure 1
Figure 1. Distribution of mean daily step count.
Median is 5,232 steps per day, N = 169.
See this image and copyright information in PMC

References

    1. Mannino DM, Braman S (2007) The epidemiology and economics of chronic obstructive pulmonary disease. Proc Am Thorac Soc 4: 502–506. - PubMed
    1. Rabe KF, Hurd S, Anzueto A, Barnes PJ, Buist SA, et al. (2007) Global Initiative for Chronic Obstructive Lung Disease. Global strategy for the diagnosis, management, and prevention of chronic obstructive pulmonary disease: GOLD executive summary. Am J Respir Crit Care Med 176: 532–555. - PubMed
    1. Kocks JW, Asijee GM, Tsiligianni IG, Kerstjens HA, van der Molen T (2011) Functional status measurement in COPD: a review of available methods and their feasibility in primary care. Prim Care Respir J 20: 269–725. - PMC - PubMed
    1. Puhan MA, Chandra D, Mosenifar Z, Ries A, Make B, et al. (2011) The minimal important difference of exercise tests in severe COPD. Eur Respir J 37: 784–790. - PMC - PubMed
    1. Moy ML, Matthess K, Stolzmann K, Reilly J, Garshick E (2009) Free-living physical activity in COPD: assessment with accelerometer and activity checklist. J Rehabil Res Dev 46: 277–286. - PMC - PubMed

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