eTable 3.

The number and percentage of all eligible participants from the original population that consented by baseline characteristics and randomization group

	Combined hormone therapy (n=7878 eligible)		Placebo (n=7530 eligible)
	N	%	N	%	P-Value
Overall	6545	83.1	6243	82.9	0.78
Age group at screening					0.86
50-59	2266	84.0	2128	83.8
60-69	3019	84.1	2887	84.3
70-79	1260	79.2	1228	78.5
Race/ethnicity					0.11
White	5616	85.0	5357	84.5
Black	406	80.2	401	77.1
Hispanic	291	65.1	261	66.9
American Indian	16	66.7	14	56.0
Asian/Pacific Islander	132	74.2	128	82.6
Unknown	84	72.4	82	82.0
Education					0.46
0-8 years	94	51.4	90	57.3
Some high school	230	71.4	238	72.6
High school diploma/GED	1254	83.7	1225	81.6
School after high school	2569	82.5	2329	82.7
College degree or higher	2363	86.8	2317	86.7
Gail 5 year risk					0.54
< 1.25	2117	80.2	2041	80.1
1.25 - < 1.75	2237	84.4	2125	85.0
≥ 1.75	2191	84.7	2077	83.7
Age at menarche					0.04
≤11	1372	85.5	1279	82.5
12-13	3539	83.4	3377	83.8
≥ 14	1617	80.4	1563	81.6
Years since menopause					0.54
< 5 yrs	1617	85.3	1563	84.6
5 - <10 yrs	1071	86.3	988	85.4
10 - <15 yrs	1199	83.2	1206	84.7
≥ 15 yrs	1267	81.2	1242	80.5
Number of term pregnancies					0.51
Never pregnant/Never had term pregnancy	661	83.0	627	82.8
Mean ± SD	529	83.0	488	80.1
Age at first birth, y (categories)					>0.99
Never pregnant/No term pregnant	661	83.0	627	82.8
< 20	825	80.6	820	80.0
20 - 29	3913	84.4	3702	84.1
30+	564	84.3	482	83.7
Number of months breastfed					0.70
Never brstfd	2912	82.7	2782	81.8
brstfd ≤ 1 year	2416	82.7	2285	83.0
brstfd > 1 year	1152	85.6	1103	85.5
Oral contraceptive use ever	2960	85.4	2789	85.7	0.50
Oral contraceptive duration					0.36
< 5 yrs	1564	84.4	1438	85.7
5 - < 10 yrs	669	86.0	667	86.1
≥ 10 yrs	726	86.9	681	85.2
Unopposed estrogen use ever	682	82.5	645	81.5	0.68
Unopposed estrogen use					0.59
Non-user	5863	83.3	5598	81.3
< 5 yrs	518	83.2	496	83.1
≥ 5 yrs	164	80.0	148	82.2
Estrogen + progesterone use ever	1215	85.0	1131	85.9	0.40
Estrogen + Progest Duration					0.67
Non-user	5330	82.6	5112	82.3
< 5 yrs	840	84.4	798	85.3
≥ 5 yrs	375	86.4	333	87.6
Number of first deg female relatives with breast cancer					0.74
None	5371	84.9	5149	84.7
1	715	83.1	633	82.8
2 or more	58	80.6	63	85.1
Benign breast disease					0.89
No	4904	83.1	4843	83.0
Yes, 1 biopsy	740	84.6	759	83.6
Yes, 2+ biopsies	222	82.2	218	81.3
Body-mass index (kg/m2), baseline					0.03
< 25	1998	84.4	1949	84.1
25 - < 30	2278	81.9	2215	83.6
≥ 30	2240	83.1	2038	80.9
Dietary energy (kcal)					0.96
≤ 1322 kcal	1996	80.8	1966	80.7
1322 < - 1841 kcal	2215	85.0	2117	85.2
> 1841 kcal	2130	83.6	1980	83.6
Percent energy from fat					0.78
≤ 29.6 percent	2157	85.5	2065	84.8
29.6 < - 37.2 percent	2114	82.8	2077	83.0
> 37.2 percent	2070	81.3	1921	81.6
Physical act (METS/wk)					0.85
≤ 3.5 METS/wk	1996	81.4	1913	80.5
3.5 < - 12.8 METS/wk	1940	83.7	1936	83.6
> 12.8 METS/wk	1987	84.7	2010	84.7
Alcohol use					0.54
Non Drinker	2671	80.5	2559	80.3
≤ 1 drink/day	3003	84.4	2832	84.7
> 1 drink/day	844	87.3	828	85.7
Smoking status					0.63
Never	3288	83.1	3139	83.3
Past	2597	84.1	2452	83.9
Current	600	79.4	577	77.3
NSAIDs	2194	83.5	2133	83.4	0.96

Due to information missing for some variables, category denominators do not always equal group total shown in column heading.

Gail risk score incorporates age, history of benign disease (atypia staus unknown in the Women's Health Initiative), age at menarche, age at first live birth, race/ethnicity, and numbers of mothers and sisters with breast cancer

NSAIDs = use of aspirin, ibuprofen, prescription NSAIDs, or the related analgesic, acetaminophen

Time from menopause was defined as previously described¹⁵, as the interval from the onset of menopause to first menopausal hormone therapy use or first use of study medication (hormone or placebo).

As seen, consent rates were comparable for demographic and risk factor distribution for the two randomization groups.