Table 3.

—Multivariate Regression Models Predicting Physical Activity, Total Steps per Day (N = 148)

	Unstandardized Coefficients		Standardized Coefficients
Variable	β	SE	β	P Value	R2	∆R2
Model 1					0.20	0.20
Age, per y	−116	32	0.74	<.001
Male sex	955	668	0.11	.16
FEV1 % predicteda	76	19	0.32	<.001
O2 use	−547	608	−0.07	.37
Model 2b					0.32	0.12
Dyspnea, SOBQ	−79	16	−0.38	<.001
Model 3b					0.42	0.10
Dyspnea, SOBQ	−52	16	−0.25	.001
6MWT, ft	3	0.68	0.38	<.001
Model 4b					0.42	0
Dyspnea, SOBQ	−51	17	−0.24	.003
6MWT, ft	3	0.68	0.38	<.001
Depression, HADS-D	−23	65	−0.03	.73
Model 5b					0.47	0.04
Dyspnea, SOBQ	−57	16	−0.27	.001
6MWT, ft	3	0.65	0.39	<.001
Depression, HADS-D	−176	76	−0.19	.02
Anxiety, HADS-A	288	80	0.32	<.001
Model 6c					0.42	…
6MWT, ft	4	0.64	0.48	<.001
Depression, HADS-D	−228	77	−0.25	.004
Anxiety, HADS-A	257	83	0.29	.002

∆R² = change in R²; SOBQ = Shortness of Breath Questionnaire. See Table 1 legend for expansion of other abbreviations.

^aFor each 1% change in FEV₁.

^bModels 2-5 included age, sex, FEV₁% predicted, and supplemental O₂ use.

^cDyspnea excluded from model 6; comparing models 5 and 6 provides a test of mediation to examine whether dyspnea mediates the relationship between the anxiety and physical activity.