Table 1.

Characteristics of myocardial infarction cases and matched controls

Total	Cases		Controls		P‡
	183 (N)	100 (%)∗	182† (N)	100 (%)∗
Age at breast cancer diagnosis§
Median age (IQR) in years	50.2	45.8-54.7	50.2	45.5-54.6
<40 (22-39) y	9	4.9	10	5.5
40-49 y	78	42.6	78	42.9
50-59 y	77	42.1	75	41.2
≥60 (60-70) y	19	10.4	19	10.4
Year of breast cancer diagnosis§
1970-1979	41	22.4	41	22.5
1980-1989	95	51.9	92	55.6
1990-1999	29	15.9	34	18.7
2000-2009	18	9.8	15	8.2
Time to MI/cutoff date§,¶
Median time (IQR) in years	13.6	10.3-18.2	13.7	10.3-18.2
<5 (1-4) y	13	7.1	13	7.1
5-9 y	31	16.9	31	17.0
10-14 y	60	32.8	59	32.4
15-19 y	48	26.2	48	26.4
≥20 (20-29) y	31	16.9	31	17.0
Age at MI diagnosis/cutoff date¶
Median age (IQR) in years	64.2	58.5-70.2	63.9	58.5-70.2
<50 (40-49) y	7	3.8	8	4.4
50-59 y	51	27.9	50	27.5
60-69 y	74	40.4	74	40.7
70-79 y	45	24.6	44	24.2
≥80 (83-89) y	6	3.3	6	3.3
Laterality of breast cancer
Right	85	46.4	81	44.5
Left	98	53.6	101	55.5	.72
Nodal status
Negative	106	57.9	107	58.8
Positive	75	41.0	74	40.7
Unknown	2	1.1	1	0.5	.91
Tumor size∗
<2 cm	58	31.7	76	41.8
2-5 cm	88	48.1	72	39.6
≥5 cm	6	3.3	10	5.5
Unknown	31	16.9	24	13.2	.09

Abbreviations: BC = breast cancer; IQR = interquartile range; MI = myocardial infarction.

^∗Percentages may not total 100 because of rounding.

^†Cases and controls were selected with replacement. When an individual appeared as a control twice within the same stratum, it was included only once in the analysis (n = 1).

^‡P value for difference between tumor characteristics of cases and controls, calculated within strata (defined by matching variables) and excluding the unknown category.

^§Matching variables.

^¶Derived from matching factors. Cutoff date for controls was defined as the date of BC diagnosis plus a time interval equal to the time between BC diagnosis and MI diagnosis for the paired case.