Table 1.

Socio-demographic distribution of cases and controls, Henan province, 2013

Variables		Case (287)		Control (291)		Total (578)
		n	%	n	%	n	%
Sex
	Female	58	20.21	89	30.58	147	25.43
	Male	229	79.79	202	69.42	431	74.57
Age (years)
	≤29	39	13.59	29	9.96	68	11.76
	30–59	64	22.3	68	23.37	132	22.84
	≥60	184	64.11	194	66.67	378	65.4
Nationality
	Han Nationality	251	87.34	241	82.75	492	85.12
	Other Nationality	36	12.66	50	17.25	86	14.88
Religion
	Christian	20	7.12	15	5.32	35	6.05
	Muslim	7	2.42	9	2.96	16	2.77
	No religion	260	90.46	267	91.72	527	91.18
Occupation
	Unemployed	182	63.41	151	51.89	333	57.61
	Employed	105	36.59	140	48.11	245	42.39
Education degree
	High school or lower	211	73.52	157	53.95	368	63.67
	University or higher	76	26.48	134	46.05	210	36.33
Marital status
	Married	185	64.57	179	61.39	364	62.98
	Single	76	26.48	72	24.83	148	25.61
	Divorced	20	6.84	31	10.52	51	8.82
	Widowed	6	2.11	9	3.26	15	2.59
Monthly income of the Family (RMB)
	≤3000	231	80.44	228	78.35	459	79.41
	3000–5000	45	15.57	40	13.89	85	14.71
	≥5000	11	3.99	23	7.76	34	5.88
Patient residence
	Rural	197	68.49	175	60.18	372	64.36
	Urban	90	31.51	116	39.82	206	35.64
Family size
	≤3	142	49.32	156	53.74	298	51.56
	≥4	145	50.68	135	46.26	280	48.44