Table 1.

Summary characteristics at time of mammogram and by breast case status for the eight participating studies

Characteristic	Category	Cases N = 3628		Controls N = 5126
		N	%	N	%
Study type	Population-based or cohort	2439	67.2	3895	76.0
	Hospital-based	1189	32.8	1231	24.0
Age (years)	< 50	432	11.9	553	10.8
	50–59	1150	31.7	1462	28.5
	≥ 60	2046	56.4	3111	60.7
Parity	Nulliparous	431	12.1	582	11.5
	Parous	3141	87.9	4459	88.5
	Unknown	56		85
Menopausal status	Pre-menopausal	540	15.0	878	17.4
	Post-menopausal	3058	85.0	4194	82.6
	Unknown	30		54
Postmenopausal HT use in post-menopausal women	Ever	1737	59.6	2116	57.4
	Never	1179	40.4	1568	42.6
	Unknown	142		510
BMI (kg/m2)	< 25	1542	42.9	2095	41.3
	≥ 25	2049	57.1	2982	58.7
	Unknown	37		49
Family history breast cancer in first degree relatives	No	2808	81.5	3944	85.1
	Yes	637	18.5	688	14.9
	Unknown	183		494

HT hormone therapy