Risk of death and cardiovascular events in initially healthy women with new-onset atrial fibrillation.

Context: The risks associated with new-onset atrial fibrillation (AF) among middle-aged women and populations with a low comorbidity burden are poorly defined.

Objectives: To examine the association between incident AF and mortality in initially healthy women and to evaluate the influence of associated cardiovascular comorbidities on risk.

Design, Setting, And Participants: Between 1993 and March 16, 2010, 34,722 women participating in the Women's Health Study underwent prospective follow-up. Participants were 95% white, older than 45 years (median, 53 [interquartile range {IQR}, 49-59] years), and free of AF and cardiovascular disease at baseline. Cox proportional hazards models with time-varying covariates were used to determine the risk of events among women with incident AF. Secondary analyses were performed among women with paroxysmal AF.

Main Outcome Measures: Primary outcomes included all-cause, cardiovascular, and noncardiovascular mortality. Secondary outcomes included stroke, congestive heart failure, and myocardial infarction.

Results: During a median follow-up of 15.4 (IQR, 14.7-15.8) years, 1011 women developed AF. Incidence rates per 1000 person-years among women with and without AF were 10.8 (95% confidence interval [CI], 8.1-13.5) and 3.1 (95% CI, 2.9-3.2) for all-cause mortality, 4.3 (95% CI, 2.6-6.0) and 0.57 (95% CI, 0.5-0.6) for cardiovascular mortality, and 6.5 (95% CI, 4.4-8.6) and 2.5 (95% CI, 2.4-2.6) for noncardiovascular mortality, respectively. In multivariable models, hazard ratios (HRs) of new-onset AF for all-cause, cardiovascular, and noncardiovascular mortality were 2.14 (95% CI, 1.64-2.77), 4.18 (95% CI, 2.69-6.51), and 1.66 (95% CI, 1.19-2.30), respectively. Adjustment for nonfatal cardiovascular events potentially on the causal pathway to death attenuated these risks, but incident AF remained associated with all mortality components (all-cause: HR, 1.70 [95% CI, 1.30-2.22]; cardiovascular: HR, 2.57 [95% CI, 1.63-4.07]; and noncardiovascular: HR, 1.42 [95% CI, 1.02-1.98]). Among women with paroxysmal AF (n = 656), the increase in mortality risk was limited to cardiovascular causes (HR, 2.94; 95% CI, 1.55-5.59).

Conclusion: Among a group of healthy women, new-onset AF was independently associated with all-cause, cardiovascular, and noncardiovascular mortality, with some of the risk potentially explained by nonfatal cardiovascular events.