Table 2.

Basic characteristics of the cases and controls

	case(N = 578)		control(N = 756)
Variables	No.	%	No.	%	P
Age (mean ± SD)	52.07 ± 18.01		52.85 ± 18.42		0.176
Gender					0.199
Male	417	72.1	569	75.3
Female	161	27.9	187	24.7
Education					< 0.001
Illiterate or semi-illiterate	164	28.4	89	11.8
Primary school	133	23	215	28.4
Junior high school	201	34.8	267	35.3
Senior high school or above	80	13.8	185	24.5
Smoking					0.003
Ever	299	52.5	336	44.4
Never	270	47.5	420	55.6
Drinking					< 0.001
Ever	101	17.9	215	28.4
Never	463	82.1	541	71.6