Lifetime risk of atrial fibrillation according to optimal, borderline, or elevated levels of risk factors: cohort study based on longitudinal data from the Framingham Heart Study

Abstract

Objective: To examine the association between risk factor burdens-categorized as optimal, borderline, or elevated-and the lifetime risk of atrial fibrillation.

Design: Community based cohort study.

Setting: Longitudinal data from the Framingham Heart Study.

Participants: Individuals free of atrial fibrillation at index ages 55, 65, and 75 years were assessed. Smoking, alcohol consumption, body mass index, blood pressure, diabetes, and history of heart failure or myocardial infarction were assessed as being optimal (that is, all risk factors were optimal), borderline (presence of borderline risk factors and absence of any elevated risk factor), or elevated (presence of at least one elevated risk factor) at index age.

Main outcome measure: Lifetime risk of atrial fibrillation at index age up to 95 years, accounting for the competing risk of death.

Results: At index age 55 years, the study sample comprised 5338 participants (2531 (47.4%) men). In this group, 247 (4.6%) had an optimal risk profile, 1415 (26.5%) had a borderline risk profile, and 3676 (68.9%) an elevated risk profile. The prevalence of elevated risk factors increased gradually when the index ages rose. For index age of 55 years, the lifetime risk of atrial fibrillation was 37.0% (95% confidence interval 34.3% to 39.6%). The lifetime risk of atrial fibrillation was 23.4% (12.8% to 34.5%) with an optimal risk profile, 33.4% (27.9% to 38.9%) with a borderline risk profile, and 38.4% (35.5% to 41.4%) with an elevated risk profile. Overall, participants with at least one elevated risk factor were associated with at least 37.8% lifetime risk of atrial fibrillation. The gradient in lifetime risk across risk factor burden was similar at index ages 65 and 75 years.

Conclusions: Regardless of index ages at 55, 65, or 75 years, an optimal risk factor profile was associated with a lifetime risk of atrial fibrillation of about one in five; this risk rose to more than one in three a third in individuals with at least one elevated risk factor.

Fig 1

Selection of study sample with index age 55 years

Fig 2

Cumulative risk (%) for atrial fibrillation according to risk factor burden (optimal, borderline, or elevated) at index age 55 years. Shading=95% confidence intervals. Participants entered the study sample between ages 55 and <60 years; therefore, the number at risk increased from age 55 years to <60 years

Fig 3

Predicted lifetime risk (%) of atrial fibrillation at index age 55 years across 16 risk profiles, in men and women. Profiles were defined according to treatment for hypertension (yes or no), body mass index (25 or 35), alcohol (elevated (E) or optimal (O)), and history of myocardial infarction or heart failure (yes or no). For each profile, participants with an average blood pressure level (mean systolic blood pressure 128 mm Hg and 124 mm Hg and mean diastolic blood pressure 80 mm Hg and 76 mm Hg for men and women, respectively), who never smoked, and who had no diabetes were considered