Table 1. Characteristics at recruitment of cases and controls, Breakthrough Generations Study, United Kingdom.

	Cases		Controls
Characteristic	No.a	%	No.a	%
Age at entry (years)
<60	121	45.7	152	44.3
60–69	130	49.1	165	48.1
⩾70	14	5.3	26	7.6
Year of entry to the study
<2006	132	49.8	155	45.2
2006	71	26.8	103	30.0
2007	40	15.1	55	16.0
⩾2008	22	8.3	30	8.8
Days blood sample in post
0–1	216	82.1	278	81.3
2	23	8.8	28	8.2
⩾3	24	9.1	36	10.5
Age at mammogram (years)
<60	123	46.4	146	42.7
60–69	131	49.4	175	51.2
⩾70	11	4.2	21	6.1
Time of mammogram compared with diagnosis or index date
<1.0 year earlier	16	6.0	76	22.2
1–1.9 years earlier	39	14.7	101	29.5
2–2.9 years earlier	96	36.2	103	30.1
⩾3.0 years earlier	114	43.0	62	18.1
Timing of mammogram compared with blood draw
2–3 years earlier	61	23.0	46	13.5
1–1.9 years earlier	57	21.5	60	17.5
Within 12 months	99	37.4	149	43.6
1–1.9 years later	22	8.3	32	9.4
⩾2.0 years later	26	9.8	55	16.1
Age at menarche (years)
<13	94	39.2	143	46.4
13	67	27.9	74	24.0
⩾14	79	32.9	91	29.6
Age at first birth and parity
Nulliparous	27	10.2	36	10.5
<25 years/1–2 children	55	20.8	85	24.8
<25 years/⩾3 children	30	11.3	69	20.1
25–29 years/1–2 children	67	25.3	84	24.5
25–29 years/⩾3 children	39	14.7	29	8.5
⩾30 years/1–4 children	47	17.7	40	11.7
Age at menopause (years)
<50	51	28.7	81	35.7
50–54	99	55.6	123	54.2
⩾55	28	15.7	23	10.1
Former use of postmenopausal hormone therapy (years)
Never	144	56.7	160	50.2
<5	32	12.6	51	16.0
5–9	45	17.7	56	17.6
⩾10	33	13.0	52	16.3
Body mass index (kg m−2)
<25.0	120	45.8	162	47.8
25.0–29.9	97	37.0	128	37.8
⩾30.0	45	17.2	49	14.5
Alcohol consumption (g per day)
None	52	20.0	68	20.1
<5	36	13.9	48	14.2
5–14	88	33.9	91	26.9
⩾15	84	32.3	131	38.8
Family history of breast cancer (yes)	66	24.9	57	16.6
History of benign breast disease (yes)	93	35.4	86	25.2
Total	265	100.0	343	100.0

^aNumbers do not always add up to the total owing to missing values.