COMMENTARY

The Best Treatment for COPD

Nicholas Gross, MD, PhD

Disclosures

December 08, 2011

Physical Activity Is the Strongest Predictor of All-Cause Mortality in Patients With COPD: A Prospective Cohort Study

Waschki B, Kirsten A, Holz O, Müller KC, Meyer T, Watz H, Magnussen H
Chest. 2011;140:331-342

Study Summary

There have been previous indications from various studies that patients with chronic obstructive pulmonary disease (COPD) who undergo pulmonary rehabilitation have better outcomes than those who do not. Relevant outcomes included survival, frequency of acute exacerbations, and emotional status. But validation of that view requires a prospective longitudinal study. A related question is whether the level of physical activity of a patient is predictive of their survival. Waschki and colleagues conducted a prospective study of 170 patients with moderate or severe COPD according to GOLD criteria (Global Initiative on Obstructive Lung Disease).[1] Their daily physical activity level was measured with an accelerometer that was worn as an armband. Other baseline measurements included lung function, cardiovascular function, a standardized 6-minute walking test, body mass index (BMI), ankle-brachial index, nutritional status, and a variety of metabolic blood tests. The median follow-up time was 4 years.

The primary outcome was all-cause mortality, which was 15.4% overall. There was a clear and significant relationship between physical activity level and survival. After adjustments for cofactors, including age, disease severity, etc, physical activity level remained the strongest predictor of survival.

Viewpoint

Until about 2 decades ago, lung function as measured with the forced expiratory volume in 1 second (FEV1) test was taken to be the best indicator of survival and indeed it does correlate with mortality. However, it was clear that lung function alone was not a strong predictor and that other factors consistent with the highly variable phenotypes of COPD were also important. In 2004, Celli and colleagues devised and validated the BODE Index, a composite of BMI, airflow Obstruction, a Dyspnea index, and Exercise capacity as measured by the 6-minute walk.[2] This proved to be more predictive than the FEV1, and attempts to improve it have been only marginally successful.

The present study comes from a group that is renowned for its contributions to physical rehabilitation and the many components and comorbidities of COPD; its focus is correspondingly on physical activity level as a predictor or mortality. It overlaps the components of the BODE index, but is not intended to be used as an index akin to the BODE index.

What is the message? In a nutshell, it is that among COPD patients, physically active ones are less likely to die than those who are not physically active when all other factors are compensated for. Is that because physical activity prolongs life, or because healthier patients are capable of more physical activity?

If the answer is the former, one could promote physical activity as a disease-modifying treatment. Although that question is not answered by this study, it adds further support to the advice we give to our patients that physical activity is beneficial, especially for those who may be limited by COPD.

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