Table 4. Odds ratios (ORs) and 95% confidence intervals (CIs) for adenocarcinomas and squamous cell carcinomas of the cervix in relation to smoking.

	Adenocarcinoma			Squamous cell carcinoma			Squamous vs adenocarcinoma
	Cases/controls	ORa	95% CI	Cases/controls	ORb	95% CI	Squamous/adeno cases	ORc	95% CI
Smoking status
Never	72/394	1.00		121/394	1.00		121/72	1.00
Ever	108/529	0.80	0.56–1.13	270/529	1.05	0.79–1.40	270/108	1.50	0.99–2.27
Past	32/181	0.75	0.46–1.20	60/181	0.70	0.47–1.03	60/32	1.05	0.60–1.85
Current	76/348	0.82	0.56–1.21	210/348	1.26	0.93–1.71	210/76	1.74	1.11–2.71
Age started smoking
Never	72/394	1.00		121/394	1.00		121/72	1.00
10–16 years	60/300	0.71	0.47–1.08	165/300	1.07	0.77–1.47	165/60	1.68	1.04–2.72
17+ years	48/229	0.91	0.59–1.38	105/229	1.04	0.74–1.47	105/48	1.31	0.80–2.16
Heterogeneity between groups within ever smokers			P=0.1			P=0.8			P=0.06
Total duration for current smokers
Never/<1 month	72/394	1.00		121/394	1.00		121/72	1.00
⩽10 years	8/43	0.85	0.34–2.12	22/43	0.69	0.35–1.37	22/8	1.08	0.40–2.91
10–20 years	37/192	0.72	0.44–1.18	116/192	1.13	0.79–1.62	116/37	1.66	0.96–2.85
20+ years	31/113	0.80	0.46–1.39	72/113	2.05	1.29–3.26	72/31	2.44	1.26–4.72
Trend within current smokers			P=0.3			P=0.05			P=0.04
Intensity (cigarettes per day) for current smokers
Never	72/394	1.00		121/394	1.00		121/72	1.00
<15	39/194	0.72	0.45–1.15	109/194	1.28	0.90–1.82	109/39	1.92	1.13–3.25
15+	37/154	0.82	0.51–1.34	101/154	1.26	0.86–1.83	101/37	1.68	0.97–2.92
Heterogeneity between groups within current smokers			P=0.8			P=0.8			P=0.9

OR_a, odds ratio for adenocarcinoma vs controls; OR_b, odds ratio for squamous cell carcinoma vs controls; OR_c, odds ratio for squamous cell carcinoma cases vs adenocarcinoma cases; all adjusted for age, region, total number of sexual partners, age at first intercourse, duration of oral contraceptive use, number of negative screening results and education.