Table 1.

Baseline Characteristics in the WHI E+P Trial by Breast Tenderness at Baseline and Year 1 (N=16608)¹

	Breast Tenderness (Baseline Status/Year 1 Status)
	No/No (N=10176)		No/Yes (N=3247)		Yes/No (N=717)		Yes/Yes (N=1037)
Characteristic	N	%	N	%	N	%	N	%	P1	P2
Age at screening, mean years (SD)	63.3	(7.1)	64.1	(6.9)	61.8	(7.2)	62.3	(7.1)	<0.001	<0.001
Treatment assignment
Placebo	5785	56.8	770	23.7	411	57.3	448	43.2	0.91	<0.001
CEE + MPA	4391	43.2	2477	76.3	306	42.7	589	56.8
Ethnicity
White	8840	86.9	2747	84.6	568	79.2	806	77.7	<0.001	0.001
Black	569	5.6	207	6.4	66	9.2	108	10.4
Hispanic	383	3.8	156	4.8	54	7.5	85	8.2
American Indian	27	0.3	10	0.3	4	0.6	8	0.8
Asian/Pacific Islander	229	2.3	75	2.3	11	1.5	21	2.0
Unknown	128	1.3	52	1.6	14	2.0	9	0.9
Alcohol intake
Non drinker	4186	41.3	1366	42.2	321	44.9	518	50.0	<0.001	0.25
≤ 1 drink/day	4560	45.0	1461	45.1	333	46.6	439	42.4
> 1 drink/day	1391	13.7	409	12.6	61	8.5	78	7.5
Smoking
Never smoked	5023	49.9	1636	50.9	351	49.6	518	50.4	0.88	0.03
Past smoker	3980	39.5	1306	40.6	284	40.2	400	38.9
Current smoker	1061	10.5	275	8.5	72	10.2	109	10.6
Body mass index (BMI), kg/m2 (collapsed categories)
<25	3203	31.7	1060	32.8	143	20.0	274	26.6	<0.001	0.04
25-<30	3528	34.9	1170	36.2	250	35.0	359	34.8
≤30	3386	33.5	1005	31.1	321	45.0	399	38.7
Quartiles of physical activity, MET hrs/week
< 1.5	2088	22.2	666	22.3	168	25.7	248	26.2	<0.001	0.47
1.5 ≥ to < 6.5	2181	23.2	734	24.6	164	25.1	250	26.5
6.5 ≥ to < 15.75	2461	26.2	740	24.8	156	23.9	238	25.2
≤ 15.75	2675	28.4	845	28.3	165	25.3	209	22.1
Parity
Never pregnant/Never had term pregnancy	1062	10.5	292	9.0	65	9.1	112	10.8	0.34	0.09
1	789	7.8	268	8.3	60	8.4	93	9.0
2	2217	21.9	693	21.4	154	21.5	248	24.0
3+	6064	59.8	1985	61.3	437	61.0	582	56.2
Age at first birth, years
Never pregnant/No term pregnancy	1062	11.5	292	9.9	65	10.4	112	12.1	<0.001	0.01
<20	1301	14.1	438	14.8	118	18.8	185	19.9
20 – 29	6015	65.0	1964	66.6	391	62.5	566	60.9
30+	871	9.4	256	8.7	52	8.3	66	7.1
Number of months breastfed
Never	4557	45.2	1439	44.9	331	46.6	513	49.9	0.001	0.85
≥ 1 year	3747	37.2	1190	37.1	270	38.0	379	36.8
> 1 year	1768	17.6	579	18.0	109	15.4	137	13.3
Years since menopause
<5	1564	16.7	398	13.3	153	23.8	187	19.8	<0.001	0.39
5 – 10 yrs	1799	19.2	540	18.1	134	20.9	213	22.5
10 – 15	1972	21.1	644	21.6	136	21.2	184	19.5
≤15 yrs	4023	43.0	1405	47.0	219	34.1	361	38.2
Quartiles of 5-year Gail model risk
< 1.1	1943	19.1	598	18.4	201	28.0	272	26.2	<0.001	0.05
1.1 ≥ 5 year risk< 1.44	2712	26.7	848	26.1	175	24.4	256	24.7
1.44 ≥ 5 year risk < 1.91	2818	27.7	881	27.1	149	20.8	239	23.0
5 year risk ≤ 1.91	2703	26.6	920	28.3	192	26.8	270	26.0
Prior hormone therapy use1
No	7572	74.4	2428	74.8	518	72.2	720	69.4	<0.001	0.73
Yes	2603	25.6	819	25.2	199	27.8	317	30.6

¹Of the 16608 WHI E+P trial participants, information regarding baseline and year 1 breast tenderness was available for 15177 participants. Thus, this table excludes participants for whom information regarding breast tenderness was missing from the baseline visit (N=95), the year 1 visit (N=1303), and both the baseline and year 1 visits (N=33).

^P1compares baseline characteristics of participants with versus without baseline breast tenderness (i.e., columns 1 and 2 vs. columns 3 and 4) based on chi-squared test of association for categorical variables and two sample t-tests for continuous variables.

^P2compares baseline characteristics in participants with versus without new-onset of breast tenderness (i.e., column 1 vs. column2) adjusted for age and treatment assignment. Tests of association for age and treatment assignment are unadjusted.

¹1045 (5%) of the 16,608 WHI E + P participants were current menopausal hormone therapy users at baseline, i.e. they underwent a hormone therapy “washout period” in order to participate in the WHI E + P trial.