Table 1.

Characteristics of the Study Populations in the NHS and WHS.

	NHS		WHS
	Cases (N=943)	Controls (N=1221)	Cases (N=1919)	Non-cases (N=25981)
Mean age, yrs	57.3	58.3	55.6	54.6
Mean BMI, kg/m2	25.4	25.5	25.7	26.0
Mean physical activity, kcal/week	1024.4	1123.9	987.3	986.9
Mean alcohol consumption, gram/day	5.6	5.4	4.8	4.1
Current smoker, %	12	12	12	12
Age at menarche, ≥ 13 y, %	49	51	45	48
Nulliparous, %	7	7	16	13
Paritya, ≥ 3, %	34	31	54	56
Mean age at first birth, yrs	25.0	25.0	24.9	24.2
Postmenopausal women, %	71	73	59	54
Current PMH userb, %	54	39	74	71
Mean age at menopause, yrs	48.4	47.9	47.9	47.1
Family history of breast cancerc, %	23	16	7.7	6.2
History of benign breast diseasec, %	55	42	44.1	34.8
Median CRP (IQR), mg/L	1.6 (0.6-3.5)	1.4 (0.6-3.0)	2.0 (0.8-4.3)	2.0 (0.8-4.4)

^aAmong parous women.

^bAmong postmenopausal women.

^cUpdated every 2-year in the NHS but only baseline in the WHS.