Table 2.

Baseline characteristics of breast cancer cases and controls.

	Cases		Controls		P value#
	n	%	n	%
Overall	398		372
Age*
≤ 40	79	19.8	69	18.6	0.08
41–45	106	26.6	98	26.4
46–50	144	36.2	113	30.4
51–55	69	17.3	91	24.5
Missing	0	-	1	-
Mean (SD)	44.8	(6.2)	45.2	(6.6)	0.37
BMI
<18.5	7	2.2	4	1.1	0.05
18.5 – 25	178	55.1	166	46.0
25 – 30	81	25.1	116	32.1
> 30	57	17.6	75	20.8
Missing	75	-	11	-
Mean (SD)	25.7	(5.4)	26.3	(5.5)	0.14
Education
Up to high school	122	35.4	101	27.2	0.06
Technical school	27	7.8	34	9.2
Some college/University	196	56.8	236	63.4
Missing	53	-	1	-
Smoking status
Ever smoked	184	53.2	209	56.3	0.40
Never smoked	162	46.8	162	43.7
Missing	52	-	1	-
Family History
Yes‡	86	21.6	34	9.2	<10-5
No	312	78.4	337	90.8
Missing	0	-	1	-
Menopausal status
Pre-menopausal	296	84.0	261	82.1	0.42
Post-menopausal	56	16.0	57	17.9
Missing†	46	-	54	-
Age at menarche
Age ≤ 12	154	45.2	177	48.1	0.43
Age > 12	187	54.8	191	51.9
Missing	57	-	4	-
Age period stopped
Pre-menopausal	296	84.6	261	82.1	0.68
Age ≤ 49	39	11.1	42	13.2
Age > 49	15	4.3	15	4.7
Missing	48	-	54	-
Parity (# of live births)
Nulliparous	68	19.6	63	17.0	0.85
1 child	56	16.1	57	15.4
2 children	145	41.8	157	42.3
≥ 3 children	78	22.4	94	25.3
Missing	51	-	1	-
Age at 1st live birth
Nulliparous	68	19.7	63	17.0	0.63
≤ 24 years	126	36.4	136	36.7
> 24 years	152	43.9	172	46.4
Missing	52	-	1	-

*Age of first breast cancer diagnosis for cases and age at interview for controls

^†Uncertain or missing data

^‡ Women with first-degree relatives with breast cancer

^# χ² test for categorical variables or Student's t test (equal variance) for continuous variables