TABLE 2.

Distribution of gap time from menopause to first use of postmenopausal hormones among E+P^* users in the US Women’s Health Initiative clinical trial and observational study (enrollment, 1993–1998), according to prior use of postmenopausal hormone therapy ^†

	Gap time (years)
	No prior hormone therapy			Prior hormone therapy
	<5	5–15	>15	<5	5–15	>15
Clinical trial
% of women by prior hormone use	17	43	40	84	14	3
No. of women‡	952	2,338	2,160	1,864	302	63
Breast cancer cases(no.)	22	46	46	51	6	1
Observational study
% of women by prior hormone use	75	20	6	88	11	2
No. of women‡	4,257	1,115	338	916	113	17
Breast cancer cases (no.)	160	34	5	40	3	0

^*EþP, estrogen plus progestin.

^†Prior postmenopausal hormone therapy was defined relative to the ongoing E+P episode at Women’s Health Initiative enrollment in the observational study and relative to Women’s Health Initiative enrollment for women randomized to E+P use in the clinical trial.

^‡Excluded women for whom a gap-time value was missing.