Chest
Volume 140, Issue 2, August 2011, Pages 331-342
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Original Research
COPD
Physical Activity Is the Strongest Predictor of All-Cause Mortality in Patients With COPD: A Prospective Cohort Study

https://doi.org/10.1378/chest.10-2521Get rights and content

Background

Systemic effects of COPD are incompletely reflected by established prognostic assessments. We determined the prognostic value of objectively measured physical activity in comparison with established predictors of mortality and evaluated the prognostic value of noninvasive assessments of cardiovascular status, biomarkers of systemic inflammation, and adipokines.

Methods

In a prospective cohort study of 170 outpatients with stable COPD (mean FEV1, 56% predicted), we assessed lung function by spirometry and body plethysmography; physical activity level (PAL) by a multisensory armband; exercise capacity by 6-min walk distance test; cardiovascular status by echocardiography, vascular Doppler sonography (ankle-brachial index [ABI]), and N-terminal pro-B-type natriuretic peptide level; nutritional and muscular status by BMI and fat-free mass index; biomarkers by levels of high-sensitivity C-reactive protein, IL-6, fibrinogen, adiponectin, and leptin; and health status, dyspnea, and depressive symptoms by questionnaire. Established prognostic indices were calculated. The median follow-up was 48 months (range, 10-53 months).

Results

All-cause mortality was 15.4%. After adjustments, each 0.14 increase in PAL was associated with a lower risk of death (hazard ratio [HR], 0.46; 95% CI, 0.33-0.64; P < .001). Compared with established predictors, PAL showed the best discriminative properties for 4-year survival (C statistic, 0.81) and was associated with the highest relative risk of death per standardized decrease. Novel predictors of mortality were adiponectin level (HR, 1.34; 95% CI, 1.06-1.71; P = .017), leptin level (HR, 0.81; 95% CI, 0.65-0.99; P = .042), right ventricular function (Tei-index) (HR, 1.26; 95% CI, 1.04-1.54; P = .020), and ABI < 1.00 (HR, 3.87; 95% CI, 1.44-10.40; P = .007). A stepwise Cox regression revealed that the best model of independent predictors was PAL, adiponectin level, and ABI. The composite of these factors further improved the discriminative properties (C statistic, 0.85).

Conclusions

We found that objectively measured physical activity is the strongest predictor of all-cause mortality in patients with COPD. In addition, adiponectin level and vascular status provide independent prognostic information in our cohort.

Section snippets

Study Population

In 2006, 170 stable outpatients with COPD (128 men, 42 women) with GOLD (Global Initiative for Chronic Obstructive Lung Disease) stages I (n = 34), II (n = 57), III (n = 43), and IV (n = 36) were investigated at the Pulmonary Research Institute at Hospital Grosshansdorf, Grosshansdorf, Germany. The patients were enrolled in a prospective observational study to investigate the role of extrapulmonary effects of COPD for disease severity and disease progression. The objective measurement of

Baseline Characteristics and Survival

Patient characteristics at baseline are shown in Table 1. Twenty-six (15.4%) patients died over a median follow-up of 48 months (range, 10-53 months). There were significant differences between survivors and nonsurvivors in FEV1, inspiratory to total lung capacity ratio (IC/TLC), PAL, step counts per day, 6-min walk distance, BMI, fat-free mass index, Tei index, NT-pro-BNP, ABI, adiponectin level, degree of dyspnea, SGRQ total score and activity subdomain, and mortality risk scores. Patient

Discussion

The main finding of our study is that objectively measured physical activity is the best predictor of all-cause mortality in patients with COPD. In addition, higher levels of adiponectin and an impaired vascular status provide independent prognostic information in our cohort.

Acknowledgments

Author contributions: Dr Waschki had full access to all of the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis.

Dr Waschki: contributed to the data collection, statistical analysis, and data interpretation and wrote the first draft of the manuscript.

Dr Kirsten: contributed to the data collection and interpretation and revision of the manuscript.

Dr Holz: contributed to the data collection and interpretation and revision of the

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    Drs Watz and Magnussen contributed equally to this work.

    Funding/Support: This study was supported by Deutsche Rentenversicherung Nord. Some baseline measurements for cross-sectional analyses were supported by an unrestricted research grant from AstraZeneca Germany.

    Reproduction of this article is prohibited without written permission from the American College of Chest Physicians (http://www.chestpubs.org/site/misc/reprints.xhtml).

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