Table 4.

Risk of breast cancer in HRT users stratified by established risk markers.

	Breast cancer
	e-case1	e-ctrl.1	Crude OR (95% CI)	Adj. OR (95% CI)
Age at diagnosis
<50 years	99	444	0.96 (0.7–1.2)	0.8 (0.6–1.1)
50+ years	1393	2698	1.1 (0.99–1.2)	1.3 (1.1–1.4)
Education			P eff = 0.0	P eff = 0.0
University level	455	1089	1.2 (0.96–1.6)	1.1 (0.7–1.5)
Lower education	1037	2053	1.2 (1.0–1.3)	1.3 (1.1–1.5)
Age at menarche			P eff = 0.0	P eff = 0.0
<13 years	764	1600	1.1 (0.9–1.3)	1.1 (0.9–1.3)
13+ years	728	1542	1.1 (0.9–1.3)	1.0 (0.8–1.3)
Child bearing history			P eff = 0.0	P eff = 0.0
0–1 child	678	1167	1.1 (0.9–1.3)	1.1 (0.8–1.4)
2+ children	814	1975	1.0 (0.9–1.2)	1.0 (0.9–1.2)
Age at first live birth			P eff = 0.0	P eff = 0.0
<= 22 years	593	1255	1.1 (0.9–1.3)	1.2 (0.9–1.5)
>22 years	700	1554	1.2 (0.97–1.4)	1.2 (0.95–1.5)
Breast-feeding			P eff = 0.0	P eff = 0.0
never	838	1552	1.1 (0.9–1.2)	1.1 (0.91–1.4)
1 month and more	654	1590	1.1 (0.96–1.4)	1.3 (1.0–1.6)
OC use			P eff = 0.0	P eff = 0.0
never	461	695	1.3 (0.99–1.6)	1.4 (1.0–1.8)
ever	1031	2447	1.2 (1.0–1.3)	1.1 (0.9–1.3)
Family history of breast cancer			P eff = 0.0	P eff = 0.0
No	1261	2871	1.1 (0.97–1.2)	1.1 (1.0–1.3)
Yes	231	271	5.3 (1.8–15.5)	6.4 (1.7–24.5)
Body mass index			P eff = 0.0	P eff = 0.0
<25	617	1546	1.2 (0.99–1.5)	0.99 (0.8–1.3)
25+	875	1596	1.0 (0.9–1.2)	1.2 (1.0–1.5)
			P eff = 0.0	P eff = 0.0

Conditional logistic regression: Odds ratios and 95% confidence intervals. Crude and adjusted for age, BMI, family history of breast cancer, childbearing history, age at first live birth, duration of breast-feeding, age at menarche, age at first OC use, education. Analyses for index date 0.5 year prior to cancer diagnosis.

¹ e-case, e-ctrl = number of observations for exposed case or exposed control respectively.

P eff = Significance for effect modification