eTable 2.

Baseline characteristics of trial participants that re-consented by randomization group (n=12788)

	Combined hormone therapy (n=6545)		Placebo (n=6243)
	N	%	N	%	P-Value
Age group at screening					0.75
50-59	2266	34.6	2128	34.1
60-69	3019	46.1	2887	46.2
70-79	1260	19.3	1228	19.7
Race/ethnicity					0.97
White	5616	85.8	5357	85.8
Black	406	6.2	401	6.4
Hispanic	291	4.4	261	4.2
American Indian	16	0.2	14	0.2
Asian/Pacific Islander	132	2.0	128	2.1
Unknown	84	1.3	82	1.3
Education					0.27
0-8 years	94	1.4	90	1.5
Some high school	230	3.5	238	3.8
High school diploma/GED	1254	19.3	1225	19.8
School after high school	2569	39.5	2329	37.6
College degree or higher	2363	36.3	2317	37.4
Gail 5year risk					0.91
< 1.25	2117	32.3	2041	32.7
1.25 - < 1.75	2237	34.2	2125	34.0
≥ 1.75	2191	33.5	2077	33.3
Age at menarche					0.79
≤11	1372	21.0	1279	20.6
12-13	3539	54.2	3377	54.3
≥ 14	1617	24.8	1563	25.1
Years since menopause					0.52
< 5 yrs	1071	18.0	988	17.0
5 - <10 yrs	1199	20.2	1206	20.8
10 - <15 yrs	1267	21.3	1242	21.4
≥ 15 yrs	2410	40.5	2370	40.8
Number of term pregnancies					0.37
Never pregnant/Never had term pregnancy	661	10.1	627	10.1
1	529	8.1	488	7.9
2	1480	22.7	1319	21.2
3	1573	24.1	1538	24.7
4	1104	16.9	1103	17.7
5+	1171	18.0	1140	18.3
Age at first birth, y (categories)					0.30
Never pregnant/No term pregnant	661	11.1	627	11.1
< 20	825	13.8	820	14.6
20 - 29	3913	65.6	3702	65.7
30+	564	9.5	482	8.6
Number of months breastfed					0.96
Never brstfd	2912	44.9	2782	45.1
brstfd ≤ 1 year	2416	37.3	2285	37.0
brstfd > 1 year	1152	17.8	1103	17.9
Oral contraceptive use ever	2960	45.2	2789	44.7	0.53
Oral contraceptive duration					0.47
< 5 yrs	1564	52.9	1438	51.6
5 - < 10 yrs	669	22.6	667	23.9
≥ 10 yrs	726	24.5	681	24.4
HRT use status					0.64
Never used	4798	73.3	4619	74.0
Past user	1282	19.6	1200	19.2
Current user	462	7.1	421	6.7
Unopposed estrogen use ever	682	10.4	645	10.3	0.87
Unopposed estrogen use					0.88
Non-user	5863	89.6	5598	89.7
< 5 yrs	518	7.9	496	7.9
≥ 5 yrs	164	2.5	148	2.4
Estrogen + progesterone use ever	1215	18.6	1131	18.1	0.51
Estrogen + Progest Duration					0.61
Non-user	5330	81.4	5112	81.9
< 5 yrs	840	12.8	798	12.8
≥ 5 yrs	375	5.7	333	5.3
Time since quitting HT					0.80
Current	462	7.1	421	6.7
Past, < 5 yrs	576	8.8	531	8.5
Past, ≥ 5 yrs	706	10.8	669	10.7
Never	4798	73.3	4619	74.0
Number of first deg female relatives with breast cancer					0.30
None	5371	87.4	5149	88.1
1	715	11.6	633	10.8
2 or more	58	0.9	63	1.1
Benign breast disease					0.79
No	4904	83.6	4843	83.2
Yes, 1 biopsy	740	12.6	759	13.0
Yes, 2+ biopsies	222	3.8	218	3.7
Body-mass index (kg/m2), baseline					0.19
< 25	1998	30.7	1949	31.4
25 - < 30	2278	35.0	2215	35.7
≥ 30	2240	34.4	2038	32.9
Dietary energy(kcal)					0.43
≤ 1322 kcal	1996	31.5	1966	32.4
1322< - 1841 kcal	2215	34.9	2117	34.9
> 1841 kcal	2130	33.6	1980	32.7
Percent energy from fat					0.44
≤ 29.6 percent	2157	34.0	2065	34.1
29.6 < - 37.2 percent	2114	33.3	2077	34.3
> 37.2 percent	2070	32.6	1921	31.7
Physical act (METS/wk)					0.46
≤ 3.5 METS/wk	1996	33.7	1913	32.7
3.5 < - 12.8 METS/wk	1940	32.8	1936	33.0
> 12.8 METS/wk	1987	33.5	2010	34.3
Alcohol use					0.76
Non Drinker	2671	41.0	2559	41.1
≤ 1 drink/day	3003	46.1	2832	45.5
> 1 drink/day	844	12.9	828	13.3
Smoking status					0.94
Never	3288	50.7	3139	50.9
Past	2597	40.0	2452	39.8
Current	600	9.3	577	9.4
NSAIDs	2194	33.5	2133	34.2	0.44

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).