Table 1.

Demographics of study participants at time of recruitment to the Predicting Risk of Cancer At Screening (PROCAS) study*

	Study 1					Study 2					PROCAS
	Control subjects		Case subjects			Control subjects		Case subjects			(n = 57902)
	(n = 1098)		(n = 366)			(n = 1014)		(n = 338)
	Number	Percent	Number	Percent	P value	Number	Percent	Number	Percent	P value	Number	Percent
Age at consent (years)
< 50	117	10.7	40	10.9		50	4.9	17	5.0		7173	12.4
50–54	316	28.8	104	28.4		203	20.0	66	19.5		16962	29.3
55–59	157	14.3	53	14.5		179	17.7	61	18.0		11046	19.1
60–64	237	21.6	79	21.6		315	31.1	105	31.1		11223	19.4
65–69	197	17.9	66	18.0		210	20.7	70	20.7		8552	14.8
70+	74	6.7	24	6.6	1.000	57	5.6	19	5.6	1.000	2946	5.1
Median (IQR)	58	51–64	58	51–64	0.988	61	55–65	61	55–65	0.965	57	51–63
Menopausal status
Perimenopausal	170	15.5	57	15.6		145	14.3	49	14.5		10760	18.6
Postmenopausal	747	68.0	248	67.8		769	75.8	256	75.7		37201	64.2
Premenopausal	136	12.4	46	12.6		67	6.6	22	6.5		6869	11.9
Unknown	45	4.1	15	4.1	1.000	33	3.3	11	3.3	1.000	3072	5.3
HRT use
Never	699	63.7	250	68.3		518	51.1	177	52.4		36505	63.0
Previous	342	31.1	93	25.4		379	37.4	122	36.1		16438	28.4
Current	56	5.1	19	5.2		110	10.8	37	10.9		4421	7.6
Unknown	1	0.1	4	1.1	0.302a	7	0.7	2	0.6	0.972	538	0.9
BMI (kg/m2)
< 25	345	31.4	112	30.6		334	32.9	108	32.0		20774	35.8
25–29	353	32.1	122	33.3		346	34.1	118	34.9		18969	32.8
≥ 30	327	29.8	105	28.7		272	26.8	88	26.0		14256	24.6
Unknown	73	6.6	27	7.4	0.918	62	6.1	24	7.1	0.904	3933	6.8
Median (IQR)	27.2	24.0–31.2	27.8	24.0–30.8	0.581	26.6	23.9–30.5	26.6	23.9–30.5	0.517	26.4	23.6–30.3
Ethnic origin
White	1038	94.5	334	91.3		924	91.1	304	89.9		52689	91.0
Other/unknown	50	4.6	32	8.7	0.003	90	8.9	34	10.1	0.511	5213	9.0
Year of mammogram
2009	22	2.0	0	0.0							2372	4.1
2010	607	55.3	43	11.7		196	19.3	70	20.7		14761	25.5
2011	396	36.1	130	35.5		553	54.5	177	52.4		18350	31.7
2012	70	6.4	129	35.2		264	26.0	86	25.4		14214	24.5
2013	3	0.3	30	8.2		1	0.1	3	0.9		3499	6.0
2014	0	0.0	33	9.0		0	0.0	2	0.6		3804	6.6
2015	0	0.0	1	0.3	< 0.001b					0.769c	900	1.6
Initial Tyrer-Cuzick (10-year %)
Median (IQR)	2.72	2.18 – 3.52	2.95	2.29–3.90	0.003	2.63	2.10–3.47	2.91	2.25–4.02	< 0.001	2.67	2.12–3.47
Family history
None	803	73.1	249	68.0		754	74.4	229	67.8		42367	73.2
FDR only	104	9.5	42	11.5		107	10.6	47	13.0		5749	9.9
SDR only	147	13.4	51	13.9		126	12.4	42	12.4		7998	13.8
FDR and SDR	44	4.0	24	6.6	0.112	27	2.7	20	5.9	0.008	1788	3.1
Current alcohol use
No	283	25.8	89	24.3		273	26.9	93	27.5		15815	27.3
Yes	797	72.6	269	73.5		726	71.6	241	71.3		41130	71.0
Unknown	18	1.6	8	2.2	0.697	15	1.5	4	1.2	0.908	957	1.7
Any children
No	128	11.7	43	11.7		98	9.7	45	13.3		7384	12.7
Yes	970	88.3	323	88.3		915	90.2	290	85.8		50411	87.1
Unknown					0.963	1	0.1	3	0.9	0.023d	107	0.2
Prior biopsy of breast
No	910	82.9	284	77.6		837	82.5	252	74.6		47359	81.8
Yes	159	14.5	65	17.8		153	15.1	76	22.5		8911	15.4
Unknown	29	2.6	17	4.6	0.041	24	2.4	10	3.0	0.005	1632	2.8

^*In study 1 cases are women with breast cancer detected at first screen on entry to the PROCAS study and in study 2 cases are women with breast cancer detected within PROCAS at a subsequent screen or between screening rounds

IQR interquartile range, HRT hormone replacement therapy, BMI body mass index, FDR first-degree relative, SDR second-degree relative

^aExcludes unknown

^b2013-2015 combined

^c2012-2014 combined

^dUnknown combined with no children