Characters		Case group	Control group	t/χ²	p
Age		55.02 ± 0.82	49.95 ± 0.78	−1.815	>0.05
Gender	Male	157	142	1.599	0.206
Gender	Female	144	159	1.599	0.206
Nationality	Han	251	264	2.185	0.335
	Hui	39	28
	Other	10	9
Education	Primary and below	151	106	13.886	0.01
	Junior middle school	95	130
	High school and above	54	64
Smoking	Never	177	166	22.563	0.00
	Sometime	59	102
	Every day	49	28
	Quitted smoking	15	5
Drinking	Yes	66	68	0.017	0.896
Drinking	No	232	233	0.017	0.896