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. 2017 Jul 25;17(1):104.
doi: 10.1186/s12890-017-0444-0.

Prognosis and longitudinal changes of physical activity in idiopathic pulmonary fibrosis

Thomas Bahmer  1   2 , Anne-Marie Kirsten  3   4 , Benjamin Waschki  5   4 , Klaus F Rabe  5   4 , Helgo Magnussen  3   4 , Detlef Kirsten  5   4 , Marco Gramm  3   4 , Simone Hummler  6   7 , Eva Brunnemer  6   7 , Michael Kreuter  6   7 , Henrik Watz  3   4
Affiliations

Prognosis and longitudinal changes of physical activity in idiopathic pulmonary fibrosis

Thomas Bahmer et al. BMC Pulm Med. .

Abstract

Background: Physical activity (PA) is associated with disease severity in idiopathic pulmonary fibrosis (IPF), but longitudinal studies evaluating its prognostic value and changes over time are lacking.

Methods: We measured PA (steps per day, SPD) in a cohort of 46 IPF-patients (mean age, 67 years; mean FVC, 76.1%pred.) by accelerometry at baseline, recorded survival status during 3 years follow-up and repeated measurements in survivors. We compared the prognostic value of PA to established mortality predictors including lung function (FVC, DLCO) and 6-min walking-distance (6MWD).

Results: During follow-up (median 34 months) 20 patients (43%) died. SPD and FVC best identified non-survivors (AUROC-curve 0.79, p < 0.01). After adjustment for confounders (sex, age, therapy), a standardized increase (i.e. one SD) in SPD, FVC%pred. or DLCO%pred. was associated with a more than halved risk of death (HR < 0.50; p < 0.01). Compared to baseline, SPD, FVC, and 6MWD annually declined in survivors by 973 SPD, 130 ml and 9 m, resulting in relative declines of 48.3% (p < 0.001), 13.3% (p < 0.001) and 7.8% (p = 0.055), respectively.

Conclusion: While PA predicts mortality of IPF patients similar to established functional measures, longitudinal decline of PA seems to be disproportionally large. Our data suggest that the clinical impact of disease progression could be underestimated by established functional measures.

Keywords: Functional status (activity levels); Idiopathic pulmonary fibrosis; Longitudinal studies; Mortality; Physical exercise; Triaxial accelerometer.

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Conflict of interest statement

Ethics approval and consent to participate

The study was approved by the Ethics Committees of the Medical Association Schleswig-Holstein (AZ 038/12 II), and of the University of Heidelberg (S-200/2013), respectively. All participants provided written informed consent.

Consent for publication

Not applicable.

Competing interests

The authors declare that they have no competing interests.

Publisher’s Note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Figures

Fig. 1
Fig. 1
Kaplan-Meier survival curves for tertiles of baseline values of forced vital capacity (FVC %pred.) (a), diffusing capacity of the lung for carbon monoxide (DLCO %pred.) (b), 6-min walking distance (6MWD) (c) and steps per day (d) are displayed on the left. Longitudinal changes (i.e. baseline and follow-up values of survivors) of FVC %pred. (e), DLCO %pred. (f), 6MWD (g) and steps per day (h) are displayed as bar-charts on the right. In Kaplan-Meier survival curves solid lines represent the lowest tertile, dashed lines the mid tertile and dotted lines the highest tertile of the baseline values of FVC %pred. (a), DLCO %pred.(b), 6MWD (c) and steps per day (d), respectively. Censored data of surviving patients are represented as vertical dashes. P-values are presented within the single graphs. Bar-charts represent baseline (dark grey, left) and follow-up (light grey, right) data of FVC %pred. (e), DLCO %pred. (f), 6MWD (g) and steps per day (h). Comparissons between baseline and follow-up were made with paired t-tests and p-values were <0.001, 0.024, 0.055 and <0.001, respectively
Fig. 2
Fig. 2
Receiver operating characteristic (ROC) curves for the GAP score and the number of steps per day. The corresponding areas under the curves (AUROC) were 0.74 and 0.79, respectively
See this image and copyright information in PMC

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