Table 2

Characteristics of cases and controls by cohort participation

	1974			1989
		% cases (N = 235)	% controls (N = 235)	% cases (N = 105)	% controls (N = 105)
Age at donation
≤40	20.9	20.4	3.8	2.9
41–50	23.8	26.0	21.0	22.9
51–60	33.6	31.9	18.1	15.2
≥61	21.7	21.7	57.1	59.1
Education
<12 years	38.3	43.0	24.8	31.4
≥12 years	61.7	57.0	75.2	68.6
Family history of breast cancer
(define: mother, sister, grandmother)
No	79.2	91.1	73.3	87.6
Yes	20.9	8.9	26.7	12.4
Age at first birth
<20	18.7	19.2	22.9	22.9
20–29	40.4	35.7	51.4	49.5
≥30	6.8	4.3	1.0	3.8
Nulliparous	11.9	10.2	13.3	9.5
Missing	22.1	30.6	11.4	14.3
Age at menarche
<12	13.2	14.5	19.1	14.3
12–13	40.4	31.9	54.3	49.5
≥14	17.5	17.9	16.2	22.9
Missing	28.9	35.7	10.5	13.3
Lactation (months)
None	51.9	40.0	61.9	47.6
1–12	16.6	14.9	19.1	20.0
>12	6.0	9.8	5.7	17.1
Missing	25.5	35.3	13.3	15.2
Hormone replacement therapy
Never	58.3	48.5	65.7	54.3
Ever	16.6	14.9	20.0	24.8
Missing	25.1	36.6	14.3	21.0
Alcohol consumption
(no. of drinks/week)
Never	48.1	46.8	47.6	50.5
<1	12.8	8.1	17.1	12.4
1–3	7.7	8.1	14.3	15.2
≥4	13.2	7.2	14.3	7.6
Missing	18.3	29.8	6.7	14.3
Cigarette smoking (at donation)
Never	60.0	57.5	64.8	63.8
Former	16.6	15.7	23.8	21.0
Current	23.4	26.8	11.4	15.2
Time to diagnosis
<2			48.6
3–5 years	12.3	NA ^a	51.4	NA
6–10	17.9
11–15	28.5
≥16	41.3
Estrogen receptor status
ER-negative	11.5	NA	19.0	NA
ER-positive	33.2		66.7
Unknown	55.3		14.3