Table 2. Odds ratios (OR) and 95% confidence intervals (95% CI) of first myocardial infarction (MI) after breast cancer diagnosis associated with subject characteristics and medical history.

Characteristics	# of cases/# of controls	Univariate OR (95% CI)	Multivariatea OR (95% CI)
Race/ethnicity
Black	19/45	0.8 (0.5–1.5)	0.6 (0.3–1.1)
White	97/191	1.0 (referent)	1.0 (referent)
Other/unknown	18/26	1.4 (0.7–2.6)	1.2 (0.6–2.5)
Body mass index at MI (kg/m2) b
<25	52/105	1.0 (referent)	1.0 (referent)
25–29.9	38/79	0.9 (0.6–1.6)	0.8 (0.4–1.4)
>30	31/58	1.1 (0.6–1.9)	0.8 (0.4–1.5)
Unknown	13/20
Oral contraceptive use ever
No	93/201	1.0 (referent)	1.0 (referent)
Yes	25/43	1.5 (0.8–3.0)	1.5 (0.7–3.0)
Unknown	16/18
Use of oestrogen and/or hormone replacement therapy ever
No	60/105	1.0 (referent)	1.0 (referent)
Yes	69/147	0.8 (0.5–1.2)	0.9 (0.5–1.4)
Unknown	5/10
Smoking status at MI b
Never	70/156	1.0 (referent)	1.0 (referent)
Ever	59/100	1.3 (0.8–2.0)	1.5 (0.9–2.4)
Unknown	5/6
History of hypertension
No	34/111	1.0 (referent)	1.0 (referent)
Yes, no medication	7/28	0.8 (0.3–2.1)	0.7 (0.3–2.0)
Yes, medication	93/123	2.5 (1.5–4.0)	2.1 (1.3–3.4)
History of diabetes
No	88/217	1.0 (referent)	1.0 (referent)
Yes, no medication	8/13	1.5 (0.6–4.2)	1.5 (0.6–4.2)
Yes, medication	38/32	3.2 (1.8–5.6)	3.0 (1.6–5.6)
History of hypercholesterolemia
No	68/150	1.0 (referent)	1.0 (referent)
Yes, no medication	34/76	1.0 (0.6–1.8)	1.1 (0.6–2.0)
Yes, medication	32/36	2.0 (1.1–3.7)	1.4 (0.7–2.7)

^aMultivariate model includes categorical items for the named characteristic, histories of hypertension and diabetes, smoking and a combined item for tamoxifen and radiation treatment.

^bAs control subjects had no MI, data are from the reference date that marks the end of control subjects' at-risk period, which began at control subjects' dates of breast cancer diagnosis and extended for the duration of the matched case patients' time from breast cancer to MI diagnoses.