Table 2. Regression model for CCQ total scorea .

Model	Independent variable	R	R 2	ANOVA		B	P value	95% CI for B
				F	P value			Lower	Upper
1b		0.44	0.19	30.84	<0.0001
	Constant					1.21	<0.0001	1.07	1.34
	Heart failure					1.06	<0.0001	0.68	1.43
2c		0.48	0.23	18.82	<0.0001
	Constant					1.17	<0.0001	1.03	1.30
	Heart failure					1.00	<0.0001	0.63	1.37
	Depression					0.51	0.02	0.09	0.93

R is the measure of the correlation between the observed value and the predicted value of the dependent variable. R ² indicates the proportion of the variance in the dependent variable which can be explained by the independent variables, Β indicates values for the regression equation for predicting the dependent variable from the independent variable.

Abbreviations: ANOVA, analysis of variance; CCQ, Clinical COPD Questionnaire; CI, confidence interval.

^aStepwise regression model with dependent variable: CCQ-total score; N=130 for model 1, N=93 for model 2.

^bPredictor in model 1: heart failure. Excluded during analysis: depression, FEV₁%predicted, gender, age.

^cPredictors in model 2: heart failure, depression. Excluded during analysis: FEV₁%predicted, gender, age.

P<0.05 is considered significant (two-tailed).