Table 4.

Multiple regression analysis of plasma GDF11 in the COPD patients

Variables	GDF11
	β*	p-value
Smoking	0.23	0.078
FEV1 % predicted	0.05	0.735
6MWD	0.02	0.908
Number of steps	0.20	0.045
IL-6	−0.01	0.909
QMVC % predicted	0.31	0.093

Notes:

^*β = regression coefficient. All data were log transformed. Data were analyzed by multivariate linear regression. R² =0.50 (adjusted R² =0.42).

Abbreviations: FEV₁, forced expiratory volume in 1 second; GDF11, growth differentiation factor 11; IL-6, interleukin-6; 6MWD, 6-minute walking distance; QMVC, quadriceps maximal voluntary contraction.