Table 5.

Adjusted^a Hazard Ratios for Incident Invasive Breast Cancer, by Self-Reported Atrial Fibrillation and Glycoside Use at Baseline, Women's Health Initiative, 1994–1998

Mutually Exclusive Categories of Atrial Fibrillation and Cardiac Glycoside	Invasive Breast Cancerb					Colorectal Cancerc
	Total Sample Size	No. of Events	HR	95% CI	P Value	Total Sample Size	No. Events	HR	95% CI	P Value
No atrial fibrillation, no cardiac glycosides	61,794	3,513	1.00	Referent		72,062	1,178	1.00	Referent
Atrial fibrillation, no cardiac glycosides	2,281	121	1.01	0.85, 1.20	0.89	2,693	44	0.91	0.67, 1.23	0.54
Atrial fibrillation, cardiac glycosides	932	77	1.70	1.35, 2.13	<0.001	1,088	20	0.93	0.60, 1.46	0.76
No atrial fibrillation, cardiac glycosides	345	25	1.69	1.13, 2.50	0.01	409	9	1.18	0.61, 2.29	0.62

Abbreviations: CI, confidence interval; HR, hazard ratio.

^a The invasive breast cancer model was adjusted for baseline characteristics that were associated with both atrial fibrillation prevalence and incident breast cancer: age, race, educational level, income, marital status, physical activity level, parity, age at menopause, hormone therapy use, hysterectomy, diabetes, and history of cardiovascular disease (myocardial infarction, stroke, transient ischemic attack, angina, or revascularization). The colorectal cancer model was adjusted for baseline characteristics that were associated with both atrial fibrillation prevalence and incident colorectal cancer: age, race, income, marital status, physical activity level, parity, hormone therapy use, hypertension, diabetes, resting pulse rate, and history of cardiovascular disease (myocardial infarction, stroke, transient ischemic attack, angina, or revascularization).

^b The median follow-up time was 15.3 years.

^c The median follow-up time was 15.9 years.