Table 2

Characteristics of subjects with chronic obstructive pulmonary disease (COPD) in the early-onset group and the low exposure group^*

	Early-onset group (age <60)			Low exposure group (pack-years <20)
	Male	Female	p Value	Male	Female	p Value
	n=177 (56%)	n=139 (44%)	p Value	n=118 (49%)	n=123 (51%)	p Value
Pack-years, median (25, 75^†)	28.4 (20.4, 39.0)	24.0 (17.2, 33.2)	0.003	15.0 (10.0, 17.5)	13.1 (8.3, 17.2)	0.112
Self-reported asthma, %	39.6	64.5	<0.001	44.9	70.7	<0.001
Bronchodilator response	5.8 (11.7)	8.8 (14.0)	0.036	9.8 (16.8)	7.5 (13.6)	0.235
Occupational exposure, %	81.2	51.2	<0.001	81.0	43.9	<0.001
Educational level, %
Primary	22.0	21.6	0.194	33.9	33.9	0.003
Secondary	59.3	66.9		47.5	61.2
University	18.6	11.5		18.6	5.0
FEV₁% predicted	56.0 (17.2)	50.6 (16.9)	0.006	55.8 (16.2)	48.7 (17.6)	0.001
GOLD 3 or 4, %	31.1	41.7	0.050	35.6	50.4	0.020

Unless otherwise noted, data are presented as means (SD).
↵* 88 subjects are present in both groups.
↵† 25th and 75th percentiles.
FEV₁, forced expiratory volume in 1 s; GOLD, Global Initiative for Chronic Obstructive Lung Disease.