TABLE 3.

Hazard ratios for invasive breast cancer for E+P^* use by years from menopause to first use of postmenopausal hormones (gap time) and prior hormone therapy use in the US Women’s Health Initiative clinical trial (enrollment, 1993–1998)

	Gap time (years)†				HR* for interaction with gap time (<5 vs. ≥5 years) (p value)‡
	<5		≥5
	HR	95% CI*	HR	95% CI
No prior hormone therapy§	1.77	1.07, 2.93	0.99	0.74, 1.31	0.02
Prior hormone therapy§	2.06	1.30, 3.27	1.30	0.57, 2.99
HR for interaction with prior   hormone therapy   (no vs. yes) (p value) ¶	0.53

^*EþP, estrogen plus progestin; HR, hazard ratio; CI, con.dence interval.

^†HRs and 95% CIs were derived from Cox model analyses that strati.ed on baseline age (5-year categories) and included prior hormone therapy as a breast cancer risk factor.

^‡Controlled for HR dependence on prior hormone therapy.

^§Prior (postmenopausal) hormone therapy status was de.ned relative to enrollment in the Women’s Health Initiative clinical trial.

^¶Controlled for HR dependence on gap time (<5 vs. ≥5 years).