Table 1.

Baseline Characteristics of the 435 Women in the Women's Health Initiative Mammogram Density Ancillary Study, CEE Trial Subsample, by Random Assignment

Characteristic	CEE(n = 209)		CEE Placebo(n = 226)		P
	No.	%	No.	%
Age group at screening, years					.36
50-59	74	35.4	94	41.6
60-69	87	41.6	89	39.4
70-79	48	23.0	43	19.0
Ethnicity					.21
White	91	43.5	84	37.2
Black	80	38.3	106	46.9
Hispanic	37	17.7	33	14.6
Asian/Pacific Islander	1	0.5	3	1.3
Education					.69
High school diploma/GED or less	66	32.0	79	35.4
School after high school	93	45.1	92	41.3
College or higher	47	22.8	52	23.3
Income, $					.73
< 35,000	119	60.7	131	62.4
≥ 35,000	77	39.3	79	37.6
Years since menopause					.14
< 5	24	13.7	18	9.7
5-< 10	23	13.1	20	10.8
10-< 15	27	15.4	19	10.2
≥ 15	101	57.7	129	69.4
Years since hysterectomy					.06
< 18	66	31.9	61	27.2
18-< 25	60	29.0	89	39.7
≥ 25	81	39.1	74	33.0
Age at menarche, years					.97
≤ 12	103	49.3	110	49.1
> 12	106	50.7	114	50.9
No. of term pregnancies					.22
Never pregnant/never had term pregnancy	20	9.8	22	9.8
1-2	53	25.9	72	32.1
3-4	88	42.9	75	33.5
5+	44	21.5	55	24.6
Duration of oral contraceptive use, years					.65
Nonuser	132	63.2	132	58.4
< 5	48	23.0	55	24.3
5-< 10	15	7.2	23	10.2
10+	14	6.7	16	7.1
Lifetime HRT duration, years					.84
Never used	128	61.2	137	60.6
< 5	41	19.6	49	21.7
≥ 5	40	19.1	40	17.7
Years since last HRT use					.55
Never used HRT	128	61.2	137	60.6
Current user/≤ 1	30	14.4	26	11.5
> 1	51	24.4	63	27.9
Family history of breast cancer (female)	31	16.1	28	13.1	.39
Prior bilateral oophorectomy	69	35.9	76	38.0	.67
BMI, kg/m2					.59
Normal (< 25.0)	36	17.2	36	16.1
Overweight (25.0-29.9)	74	35.4	71	31.7
Obese (≥ 30.0)	99	47.4	117	52.2
Physical activity (METs/wk)					.83
Lower tertile	98	51.9	109	52.4
Middle tertile	54	28.6	63	30.3
Upper tertile	37	19.6	36	17.3
Smoking					.06
Never smoked	116	55.5	128	57.4
Past smoker	73	34.9	60	26.9
Current smoker	20	9.6	35	15.7
Alcohol intake, g/d					.64
Nondrinker	125	62.8	128	59.8
< 2.7	38	19.1	49	22.9
≥ 2.7	36	18.1	37	17.3

NOTE. There were no statistically significant differences between treatment arms. Categories were chosen on the basis of distribution of the variable in the entire Women's Health Initiative data set.

Abbreviations: CEE, conjugated equine estrogen; GED, General Equivalency Diploma; HRT, hormone replacement therapy; BMI, body mass index; MET, metabolic equivalent tasks.