Table 1. Characteristics of subjects in this two-stage case-control study.

	Screening Stage			Validation Stage
	Controls (N = 525)	Cases (N = 298)	P	Controls (N = 557)	Cases (N = 413)	P
Age (mean ± SD) years	58.9 ± 12.9	60.3 ± 12.8	0.132	59.0 ± 13.3	58.6 ± 13.1	0.630
Gender
Male(%)	260(49.5)	164(55.0)	0.129	341(61.2)	254(61.5)	0.929
Female(%)	265(50.5)	134(45.0)		216(38.8)	159(38.5)
Smoking status
Never(%)	403(76.8)	192(64.4)	< 0.001	365(65.5)	241(58.4)	0.023
Ever(%)	122(23.2)	106(35.6)		192(34.5)	172(41.7)
Drinking status
Never(%)	412(78.5)	219(73.5)	0.104	376(67.5)	275(66.6)	0.763
Ever(%)	113(21.5)	79(26.5)		181(32.5)	138(33.4)