Table 3. Association between menstrual and reproductive characteristics and colorectal cancer risk by educational level.

		COLORECTAL CANCER
		Primary school or less							Secondary school or University
Variablea		controls	cases	ORb	95% CI			p-val	controls	cases	ORb	95% CI			p-val	P-int.c
Premenopausal status		99	27	0.86	0.51	-	1.46	0.575	357	42	0.65	0.42	-	1.01	0.054	0.360
Nulliparity		70	29	0.71	0.44	-	1.15	0.167	208	42	0.95	0.64	-	1.41	0.798	0.366
Parous women
	Age at first birth (years)
	<25	277	164	1.00					160	42	1.00
	25–29	276	136	0.77	0.57	-	1.04	0.091	257	52	0.72	0.45	-	1.15	0.168
	>29	117	57	0.75	0.51	-	1.11	0.152	229	37	0.68	0.41	-	1.13	0.138
	Five-year trend*			0.97	0.83	-	1.13	0.671			0.91	0.74	-	1.11	0.353	0.629
	No. of children
	1–2	420	184	1.00					482	106	1.00
	3–4	212	139	1.27	0.94	-	1.70	0.116	138	22	0.54	0.32	-	0.90	0.019
	> 4	46	35	1.33	0.81	-	2.20	0.262	26	5	0.49	0.18	-	1.38	0.180
	Trend per child*			1.10	0.99	-	1.21	0.072			0.77	0.63	-	0.94	0.012	0.001
	Lactation first child (months)
	None	137	65	1.12	0.77	-	1.63	0.548	104	27	1.13	0.68	-	1.88	0.646
	1–6	323	134	1.00					359	75	1.00
	>6	139	112	1.55	1.10	-	2.18	0.012	78	12	0.68	0.35	-	1.34	0.266
	Six-month trend*			1.17	1.01	-	1.34	0.031			0.82	0.59	-	1.15	0.249	0.040
No. of miscarriages
	None	584	317	1.00					647	132	1.00
	One or more	165	70	0.81	0.59	-	1.13	0.212	209	43	1.09	0.74	-	1.62	0.657	0.686
Age at menarche (years)
	<12	134	58	0.84	0.57	-	1.22	0.353	186	45	1.51	0.98	-	2.33	0.059
	12–13	317	161	1.00					432	66	1.00
	>13	289	166	0.99	0.75	-	1.32	0.972	234	61	1.57	1.06	-	2.34	0.026
	Trend per year*			1.03	0.96	-	1.11	0.430			1.04	0.94	-	1.16	0.444	0.861
Hormonal contraception use
	Never	475	305	1.00					334	85	1.00
	Ever	274	82	0.55	0.40	-	0.75	<0.001	522	90	0.75	0.53	-	1.06	0.099	0.179
	< = 5 years	105	34	0.59	0.38	-	0.92	0.019	210	41	0.82	0.53	-	1.26	0.368
	>5 years	78	25	0.66	0.40	-	1.10	0.111	171	21	0.51	0.30	-	0.87	0.014
	Not known	91	23	0.42	0.25	-	0.70	0.001	141	28	0.94	0.57	-	1.55	0.806
Postmenopausal women
Age at menopause (years)
	< = 45	142	64	0.80	0.54	-	1.20	0.283	103	33	1.22	0.69	-	2.15	0.494
	46–49	143	79	0.95	0.65	-	1.39	0.787	116	31	1.07	0.60	-	1.90	0.815
	50–52	164	102	1.00					130	33	1.00
	>52	138	74	0.88	0.60	-	1.30	0.528	74	20	0.91	0.48	-	1.73	0.774
	Five-year trend*			1.05	0.92	-	1.21	0.465			0.87	0.71	-	1.06	0.161	0.114
Fertility time (years)
	<33	137	79	1.00					99	30	1.00
	33–36	162	93	1.00	0.67	-	1.48	0.992	107	35	1.04	0.58	-	1.85	0.904
	37–39	144	74	0.85	0.56	-	1.28	0.428	119	28	0.74	0.40	-	1.34	0.317
	>39	138	72	0.86	0.57	-	1.30	0.477	95	23	0.68	0.36	-	1.28	0.231
	Five-year trend*			1.02	0.89	-	1.16	0.774			0.87	0.71	-	1.06	0.168	0.189
Hormone therapy use
	Never	585	350	1.00					440	121	1.00
	Ever	65	10	0.30	0.15	-	0.60	0.001	59	12	0.74	0.38	-	1.47	0.393	0.064

^a Totals do not add up because of missing values.

^b Odds ratios (ORs) and 95% confidence intervals (95% CI) adjusted for age, BMI 1-year prior to the interview, family history of colorectal cancer, tobacco, hormone therapy use and hormonal contraception use (the latter two variables were excluded as confounders when analyzing their association with colorectal cancer risk). Province was included as a random effect term.

^c P-int.: P value of the interaction term between educational level and the corresponding variable.

* In italics: ORs, 95% CI and P values obtained with the corresponding variable as a continuous term.