Chest
Volume 142, Issue 2, August 2012, Pages 338-346
Journal home page for Chest

Original Research
COPD
Prognostic Value of the Objective Measurement of Daily Physical Activity in Patients With COPD

https://doi.org/10.1378/chest.11-2014Get rights and content

Background

Subjective measurement of physical activity using questionnaires has prognostic value in COPD. However, their lack of accuracy and large individual variability limit their use for evaluation on an individual basis. We evaluated the capacity of the objective measurement of daily physical activity in patients with COPD using accelerometers to estimate their prognostic value.

Methods

In 173 consecutive subjects with moderate to very severe COPD, daily physical activity was measured using a triaxial accelerometer providing a mean of 1-min movement epochs as vector magnitude units (VMUs). Patients were evaluated by lung function testing and 6-min walk, incremental exercise, and constant work rate tests. Patients were followed for 5 to 8 years, and the end points were all-cause mortality, hospitalization for COPD exacerbation, and annual declining FEV1.

Results

After adjusting for relevant confounders, a high VMU decreased the mortality risk (adjusted hazard ratio [HR], 0.986; 95% CI, 0.981-0.992), and in a multivariate model, comorbidity, endurance time, and VMU were retained as independent predictors of mortality. The time until first admission due to COPD exacerbation was shorter for the patients with lower levels of VMU (adjusted HR, 0.989; 95% CI, 0.983-0.995). Moreover, patients with higher VMU had a lower hospitalization risk than those with a low VMU (adjusted incidence rate ratio, 0.099; 95% CI, 0.033-0.293). In contrast, VMU was not identified as an independent predictor of the annual FEV1 decline.

Conclusion

The objective measurement of the daily physical activity in patients with COPD using an accelerometer constitutes an independent prognostic factor for mortality and hospitalization due to severe exacerbation.

Section snippets

Subjects

We included 173 consecutive patients with COPD: postbronchodilator FEV1/FVC < 0.7 and postbronchodilator FEV1 < 80% predicted,1 cigarette smoking history of > 20 pack-years, stable condition for at least 2 months, and optimal medical therapy for at least 8 weeks. Exclusion criteria were history of asthma, depression, neuromuscular, or disabling cognitive problems; engagement in any exercise training program in the last 3 months; and other pathologic conditions or severe pain syndromes that

Results

One hundred fifty-seven men and 16 women with stable COPD were included in the study. Patient characteristics are given in Table 1.

Discussion

Our study provides an integrated evaluation of the impact of the objective measurement of daily physical activity on the prognosis of the COPD. Using a clinical cohort of patients with moderate to very severe COPD, treated according to current guidelines, we identify a linear dose-response relationship between levels of physical activity measured by an accelerometer and mortality or hospital admission. In addition to confirming that the reduction in daily physical activity is associated with a

Acknowledgments

Author contributions: Dr Garcia-Rio is the guarantor of the entire manuscript. The authors vouch for the veracity and completeness of the data and the data analyses.

Dr Garcia-Rio: contributed as the primary author, reviewing all data and writing the article.

Dr Rojo: contributed to developing the study protocol, interpreted data, contributed to and reviewed drafts of the manuscript, and approved the final version of the manuscript.

Dr Casitas: contributed to developing the study protocol, was a

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    Funding/Support: This work was supported by the Sociedad Española de Neumología y Cirugía Torácica (SEPAR) and Sociedad Madrileña de Neumología y Cirugía Torácica (NEUMOMADRID) grants.

    Reproduction of this article is prohibited without written permission from the American College of Chest Physicians. See online for more details.

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