Table 4:

Incidence of cholecystectomy and risk associated with use of oral estrogen menopausal hormone therapy

Variable	No. of women*	No. who had cholecystectomy*	Age-adjusted HR (95% CI)	Multivariate HR† (95% CI)
Never used menopausal hormone therapy	18 694	824	1.00 (ref)	1.00 (ref)
Ever used oral estrogen therapy	16 736	625	1.06 (0.96–1.16)	1.16 (1.06–1.27)
Estradiol alone	1 713	77	1.25 (0.99–1.57)	1.27 (1.01–1.60)‡
Estradiol with progestagen	15 261	533	1.03 (0.93–1,13)	1.10 (0.99–1.21)
Equine estrogen alone	585	44	1.48 (1.09–2.00)	1.53 (1.11–2.11)§
Equine estrogen with progestagen	599	23	0.95 (0.67–1.34)	0.68 (0.43–1.09)

Note: CI = confidence interval, HR = hazard ratio, ref = reference group.

^*Data on use of menopausal hormone therapy were missing for 6 250 women, including 211 who reported undergoing cholecystectomy during follow-up.

^†Adjusted for body mass index, parity, hypercholesterolemia, diabetes and education level.

^‡p = 0.2 for comparison of estradiol alone v. estradiol with progestagen; p = 0.4 for comparison of estradiol alone v. equine estrogen alone.

^§p = 0.01 for comparison of equine estrogen alone v. equine estrogen with progestagen.