Daily step count predicts acute exacerbations in a US cohort with COPD.
COPD is the fourth most common cause of death in the US, affects 5% of US adults, and accounts for a large number of hospitalizations. Persons with COPD have significantly reduced exercise capacity, measured by clinic-based tests such as the 6-minute walk test (6MWT), and reduced physical activity (PA), directly measured with accelerometers or assessed by questionnaires. In addition, lower 6MWT distance and lower daily step count, a direct and novel measure of PA, are significant predictors of all-cause mortality in COPD. COPD is also characterized by acute exacerbations (AEs) which result in poorer health-related quality of life (HRQL), a faster decline in lung function, and increased mortality.
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.
The results provide evidence for the importance of daily step count as a determinant of health status and exacerbation risk in persons with COPD. Our results suggest that there is a subgroup of COPD patients with low daily step count who have significantly increased risk of AEs and COPD-related hospitalizations, regardless of their % predicted FEV1. We speculate that the ‘‘low walker’’ may be a novel COPD phenotype. In contrast to other proposed phenotypes defined by frequent exacerbations, radiologic differences, or persistent systemic inflammation, the PA phenotype is potentially amenable to behavioral modification > from Moy et al.; PLOS ONE 8 (2013) 10p. All rights reserved to the authors and plosone.org.
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