Elsevier

Respiratory Medicine

Volume 107, Issue 11, November 2013, Pages 1740-1747
Respiratory Medicine

Functional and psychological variables both affect daily physical activity in COPD: A structural equations model

https://doi.org/10.1016/j.rmed.2013.06.002Get rights and content
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Summary

Background

Daily physical activity (DPA) level is reduced in patients with COPD. The aim of this study was to investigate the association of DPA with functional and psychological variables in these patients.

Methods

155 COPD patients (102 males, median (IQR) age 62 years (54–69 years), predicted FEV1 60% (40–75%) were included. We assessed DPA (DigiWalker SW-200), functional capacity and psychological factors.

Results

DPA level was significantly associated with all functional capacity variables and two psychological variables (Perceived Physical Ability Subscale, depression subscale of the Hospital Anxiety and Depression Scale). The six-minute walking distance and St. George Respiratory Questionnaire activity score explained 37% of the variance of DPA in a regression analysis. A structural equations model revealed that psychological variables indirectly explained DPA through functional capacity variables. DPA was stronger associated with functional capacity variables and weaker with psychological variables in patients with lower functional status than in patients with higher functional status.

Conclusions

Higher levels of DPA are associated with better functional capacity, but interestingly, DPA is also affected by psychological factors, though only indirectly, via functional capacity. The effect of specific treatment addressing psychological factors on DPA level and exercise tolerance needs further investigation. Clinical Trial Registration: ClinicalTrials.gov, NCT00614796.

Keywords

COPD
Physical activity
Functional capacity
Psychological capacity
Structural equations model

Abbreviations

6MWD
six-minute walking distance
CCQ
Clinical COPD Questionnaire
COPD
chronic obstructive pulmonary disease
DEFS
Dutch Exertion and Fatigue Scale
DPA
daily physical activity
FEV1
Forced Expiration Volume in one second
GARS
Groningen Activity and Restriction Scale
GOLD
global initiative for chronic obstructive lung disease
HADS
Hospital Anxiety and Depression Scale
IQR
interquartile range
PPAS
Perceived Physical Ability Subscale
PR
pulmonary rehabilitation
RMSEA
root mean square error of approximation
RV%TLC
residual volume as percentage of total lung capacity
SEM
structural equations modeling
SF-36
Short Form 36
SGRQ
St. George Respiratory Questionnaire
SPSS
Scientific Package of Social Sciences
SRQ-E
Self-Regulation Questionnaire for Exercise
VO2peak
peak oxygen uptake

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