Table 1. Characteristics among the study population (N=1249).

	Controls (n=877)		LSIL (n=247)		HSIL (n=125)		P-valuea
	Mean	s.d.	Mean	s.d.	Mean	s.d.
Age (year)	50.4	0.3	49.3	0.6	45.4	0.7	0.00
Marriage (marriedb/othersc) %	94.2/5.8		92.7/7.3		92.8/7.2		0.63
Occupation (farmer/others) %	37.1/62.9		36.8/63.2		33.6/66.4		0.75
Education level (primary/junior/senior) %	24.3/4.6/34.1		28.3/38.1/33.6		13.6/59.2/27.2		0.00
Annual incomed(1/2/3)%	42.0/46.6/11.4		49.0/36.8/14.2		42.4/40.8/16.8		0.04
Smoking history (% yes)	2.2		2.8		2.4		0.83
Spouse smoking history (% yes)	56.0		65.6		60.0		0.02
Abortion history (% yes)	55.3		55.5		53.6		0.93
Gynecologic disease history (% yes)	23.1		22.7		14.4		0.09
Family history (% yes)	11.9		10.9		8.0		0.44
Age at menarche (% less than 16 years old)	47.0		47.8		67.2		0.00
Age at first intercourse (% less than 23 years old)	43.2		52.6		48.8		0.02
Gravidity (% less than 3 times)	37.6		34.0		47.2		0.04
Parity (% less than 3 times)	72.5		71.7		82.4		0.05
Menopausal status (% post)	58.8		53.4		22.4		0.00
IUD use ever (% yes)	53.7		39.7		59.2		0.00

Abbreviations: LSIL, low-grade squamous intraepithelial lesions; HSIL, high-grade squamous intraepithelial lesions; IUD, intrauterine device.

^aP-value based on analysis of variance for continuous variables and χ² for categorical variables.

^bReferred as currently married.

^cIncluding for single but having sexual activity, remarried, divorced, widowed and separated women.

^dAnnual income can be divided into three levels: 1=less than 10 000 CNY, 2=10 000–30 000 CNY and 3=more than 30 000 CNY.