title: Determinants of annual change in physical activity in COPD.
abstract: Daily physical activity (PA) is reduced in patients with COPD. Previous cross-sectional analyses indicate various predictors for a low level of PA including airway obstruction, exacerbations and co-morbidities. However, information from longitudinal studies evaluating PA in the context of disease progression, survival and co-morbidities is scant.
  
  
  
  In a heterogeneous cohort of COPD patients, we annually assessed the number of steps per day over 1 week and potential determinants including lung function, exacerbations and co-morbidities. Univariable and multivariable mixed effect models were used to investigate associations between the change in steps per day (dependent variable) and possible predictors and their annual changes.
  
  
  
  A total of 177 COPD patients (46% GOLD (Global Initiative for Chronic Obstructive Lung Disease) stage 1/2, 38% stage 3 and 16% stage 4) with a mean (min/max) follow-up time of 2.7 (1/5) years were annually assessed. The number of steps per day decreased significantly over time (P < 0.001) with a mean annual change of -508 steps. The decrease in activity was significantly associated with forced expiratory volume in 1 s (FEV1) % predicted (P = 0.020) but not with annual changes in FEV1. Hyperinflation, exacerbations, co-morbidities and their annual changes, and survival did not significantly affect change in PA.
  
  
  
  COPD patients have a substantial decrease of PA over time. This decrease seems to be determined by the degree of airflow limitation. However, patients with a greater annual decline in lung function did not show a greater decrease in PA. The rate of decline in PA did not differ between survivors and non-survivors in this cohort.
authors.affiliation: Pulmonary Division, University Hospital of Zurich, Zurich, Switzerland.
authors.forename: Christian F
authors.initials: CF
authors.lastname: Clarenbach
authors.affiliation: Pulmonary Division, University Hospital of Zurich, Zurich, Switzerland.
authors.forename: Noriane A
authors.identifier: 0000-0003-1758-4586
authors.initials: NA
authors.lastname: Sievi
authors.affiliation: Epidemiology, Biostatistics and Prevention Institute, University of Zurich, Zurich, Switzerland.
authors.forename: Sarah R
authors.initials: SR
authors.lastname: Haile
authors.affiliation: Pulmonary Division, Cantonal Hospital of Glarus, Glarus, Switzerland.
authors.forename: Thomas
authors.initials: T
authors.lastname: Brack
authors.affiliation: Pulmonary Division, Cantonal Hospital of St. Gallen, St. Gallen, Switzerland.
authors.forename: Martin H
authors.initials: MH
authors.lastname: Brutsche
authors.affiliation: Pulmonary Division, Clinic Barmelweid, Barmelweid, Switzerland.
authors.forename: Martin
authors.initials: M
authors.lastname: Frey
authors.affiliation: Pulmonary Division, Cantonal Hospital of Aarau, Aarau, Switzerland.
authors.forename: Sarosh
authors.initials: S
authors.lastname: Irani
authors.affiliation: University Clinic of Internal Medicine, Cantonal Hospital Baselland and University of Basel, Basel, Switzerland.
authors.forename: Jörg D
authors.initials: JD
authors.lastname: Leuppi
authors.affiliation: Pulmonary Division, Cantonal Hospital of Münsterlingen, Münsterlingen, Switzerland.
authors.forename: Robert
authors.initials: R
authors.lastname: Thurnheer
authors.affiliation: Pulmonary Division, University Hospital of Zurich, Zurich, Switzerland.|Zurich Centre for Integrative Human Physiology, University of Zurich, Zurich, Switzerland.
authors.forename: Malcolm
authors.initials: M
authors.lastname: Kohler
mesh_terms: D000368:Aged; D015897:Comorbidity; D018450:Disease Progression; D015444:Exercise / Q000502:physiology*; D005260:Female; D005541:Forced Expiratory Volume; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D029424:Pulmonary Disease, Chronic Obstructive / Q000503:physiopathology*; D012720:Severity of Illness Index; D015996:Survival Rate; D013997:Time Factors
keywords: activity monitor; airflow limitation; chronic obstructive pulmonary disease; co-morbidities; physical activity level