Table 5. Adjusted odds ratio (95% CIs) of cervical cancer for quartiles of serum antioxidant vitamin concentrations by passive-smoking status in Chinese women.

	Quartiles of serum antioxidant vitamin concentrations				P-trend	P-interaction
	Q1	Q2	Q3	Q4
Serum retinol						0.002
N (case/control)	76/63	59/62	46/63	48/63
Passive smokers	1.00	0.88 (0.55, 1.40)	0.59 (0.36, 0.95)	0.46 (0.28, 0.76)	0.001
N (case/control)	55/119	57/119	56/119	60/119
Non-passive smokers	1.00	0.96 (0.60, 1.54)	1.04 (0.65, 1.67)	1.28 (0.81, 2.03)	0.249
Serum α-carotene						0.222
N (case/control)	67/62	66/63	54/63	33/63
Passive smokers	1.00	0.91 (0.57, 1.44)	0.78 (0.48, 1.26)	0.47 (0.28, 0.79)	0.005
N (case/control)	58/119	64/119	61/119	45/119
Non-passive smokers	1.00	1.13 (0.72, 1.78)	1.02 (0.65, 1.61)	0.76 (0.47, 1.24)	0.241
Serum β-carotene						0.002
N (case/control)	95/63	54/63	34/62	37/63
Passive smokers	1.00	0.54 (0.34, 0.87))	0.34 (0.21, 0.56)	0.36 (0.21, 0.61)	<0.001
N (case/control)	60/119	66/119	52/119	50/119
Non-passive smokers	1.00	1.07 (0.69, 1.66)	0.86 (0.54, 1.36)	0.96 (0.61, 1.51)	0.637
Serum vitamin E						0.001
N (case/control)	105/63	46/62	44/63	25/63
Passive smokers	1.00	0.44 (0.27, 0.70)	0.40 (0.25, 0.65)	0.27 (0.16, 0.46)	<0.001
N (case/control)	62/119	61/119	53/119	52/119
Non-passive smokers	1.00	0.98 (0.63, 1.53)	0.85 (0.54, 1.33)	0.81 (0.52, 1.28)	0.298
Serum vitamin C						0.004
N (case/control)	103/62	49/63	44/63	24/63
Passive smokers	1.00	0.47 (0.30, 0.74)	0.44 (0.27, 0.71)	0.23 (0.13, 0.41)	<0.001
N (case/control)	64/119	65/119	51/119	48/119
Non-passive smokers	1.00	1.01 (0.65, 1.56)	0.78 (0.50, 1.21)	0.72 (0.45, 1.14)	0.096

Adjusted ORs (95% CI): from unconditional logistic models; Covariates adjusted: see Table 3.