Table 1.

Distribution of potential and established risk factors for breast cancer among cases and controls

	Cases n = 731	(%)	Controls n = 1 669	(%)	Chi-square testa
Ageb (years)					p = 0.002
45–49	95	13.0	333	20.0
50–54	110	15.1	258	15.5
55–59	208	28.5	411	24.6
60–64	170	23.3	365	21.9
65–69	86	11.8	181	10.8
70–74	62	8.5	121	7.3
Parity					p = 0.153
0	101	14.2	211	12.8
1	139	19.5	360	21.9
2	311	43.7	665	40.4
3	125	17.6	292	17.7
≥ 4	36	5.1	118	7.2
Age at first-term pregnancy					p = 0.690
< 20	63	8.9	170	10.3
20–24	248	34.8	557	33.9
25–29	200	28.1	479	29.1
30–34	75	10.5	181	11.0
35+	25	3.5	46	2.8
No children	101	14.2	211	12.8
Months of breastfeeding/child					p = 0.002
0	24	3.5	83	5.2
1–5	343	50.3	890	55.8
6–12	205	30.1	399	25.0
≥ 13	9	1.3	11	0.7
No children	101	14.8	211	13.2
Hormone replacement therapy					p < 0.001
No treatment	508	70.5	1325	81.1
Estrogen	52	7.2	119	7.3
Progesterone	4	0.6	8	0.5
Estrogen + Progesterone	157	21.8	181	11.1
Physical activity (percentile)					p = 0.588
0–25	182	25.0	391	23.5
25–50	201	27.6	434	26.1
50–75	176	24.2	419	25.2
75–100	169	23.2	419	25.2
Alcohol (g/day)
0	35	4.9	121	7.4	p = 0.002
1–14	559	77.4	1259	76.6
15–30	101	14.0	236	14.4
> 30	27	3.7	27	1.6
Height (cm)					p = 0.289
< 160	157	21.5	407	24.4
160–169	460	62.9	1008	60.5
≥ 170	114	15.6	250	15.0
BMI					p = 0.095
< 18.5 Underweight	8	1.1	12	0.7
18.5–24.9 Normal weight	323	44.2	825	49.6
25–29.9 Overweight	276	37.8	570	34.2
≥ 30 Obese	124	17.0	258	15.5

Italic values are statistically significant at p < 0.05

^aChi-square test comparing the distribution of potential and established risk factors for breast cancer among the cases and controls

^bAge at baseline