Table 2.

Distribution of selected characteristics in the case-control study population.

Characteristics	Cases		Controls		p value
	n	%	n	%
Over all	544		550
Age (years)
Mean (±SD)	58 (±11)		58 (±11)		0.806a
≤40	29	5.3	28	5.1
41–50	99	18.2	114	20.7
51–60	193	35.5	189	34.4	0.77b
>60	223	41.0	219	39.8
Gender
Female	158	29.0	161	29.3
Male	386	71.0	389	70.7	0.93b
Family historyc
No	463	85.1	545	99.1
Yes	81	14.9	5	0.9	<0.0001b
Smoking duration
Never	196	36.0	294	53.5
≤20 (years)	96	17.6	91	16.5
>20 (years)	252	46.3	165	30.0	<0.0001b
Histology
Squamous cell carcinoma	232	42.6
Adenocarcinoma	223	41.0
Other	89	16.4

^aFor t-test.

^bFor χ² test (two-sided), boldface indicates statistical significance.

^cFamily history of cancer.