Table 1– Demographic characteristics, lung function and muscle function measurements in chronic obstructive pulmonary disease (COPD) and control groups

	COPD patients	Control subjects	p-value
Subjects n	104	100
Demographics
Age yrs	65 (56–74)	63 (54–72)	0.18
Sex M/F n	60/44	59/41	0.85
BMI kg·m⁻²	24.1±4.3	25.9±4.7	0.04
FFM index	15.8±2.0	17.6±3.3	<0.001
Smoking pack-yrs	42 (30–60)	2 (0–14)	<0.001
Daily vitamin D intake iu	199 (60–906)	254 (89–1458)	0.10
Yale physical activity score	47.7±25.9	70.9±26.4	<0.001
Yale energy expenditure kcal·week⁻¹	5176±3874	7919±4381	<0.001
Lung function
FEV₁ % pred	44±22	102±16	<0.001
FVC % pred	85±22	105±17	<0.001
T_L,CO % pred	39±16
P_a,O₂^# kPa	9.4±1.4
P_a,CO₂^# kPa	5.2±0.7
Strength measurements
QMVC kg	29.3±12.5	41.2±13.9	<0.001
TwQ kg	8.5±3.4^¶	9.5±3.1⁺	0.09
Handgrip kg	32.7±11.0	36.5±10.6	0.02
SNIP cmH₂O	64.0±20.0	80.5±24.0	<0.001

Data are presented as median (range) or mean±sd, unless otherwise stated. M: male; F: female; BMI: body mass index; FFM: fat-free mass; FEV₁: forced expiratory volume in 1 s; % pred: % predicted; FVC: forced vital capacity; T_L,CO: transfer factor of the lung for carbon monoxide; P_a,O₂: arterial oxygen tension; P_a,CO₂: arterial carbon dioxide tension; QMVC: quadriceps maximum voluntary contraction; TwQ: twitch quadriceps force; SNIP: sniff nasal inspiratory pressure. ^#: n=56; ^¶: n=71; ⁺: n=68.