PREVALENCE, INCIDENCE, PROGNOSIS, AND PREDISPOSING CONDITIONS FOR ATRIAL-FIBRILLATION - POPULATION-BASED ESTIMATES

Atrial fibrillation (AF) is the most common of the serious cardiac rhy thm disturbances and is responsible for substantial morbidity and mort ality in the general population. Its prevalence doubles with each adva ncing decade of age, from 0.5% at age 50-59 years to almost 9% at age 80-89 years. It is also becoming more prevalent, increasing in men age d 65-84 years From 3.2% in 1968-1970 to 9.1% in 1987-1989. This statis tically significant increase in men was not explained by an increase i n age, valve disease, or myocardial infarctions in the cohort. The inc idence of new onset of AF also doubled with each decade of age, indepe ndent of the increasing prevalence of known predisposing conditions. B ased on 38-year follow-up data from the Framingham Study, men had a 1. 5-fold greater risk of developing AF than women after adjustment for a ge and predisposing conditions. Of the cardiovascular risk factors, on ly hypertension and diabetes were significant independent predictors o f AF, adjusting for age and other predisposing conditions. Cigarette s moking was a significant risk factor in women adjusting only for age ( OR = 1.4), but was just short of significance on adjustment for of her risk factors. Neither obesity nor alcohol intake was associated with AF incidence in either sex. For men and women, respectively, diabetes conferred a 1.4- and 1.6-fold risk, and hypertension a 1.5- and 1.4-fo ld risk, after adjusting For other associated conditions. Because of i fs high prevalence in the population, hypertension was responsible for more AF in the population (14%) than any other risk factor. Intrinsic overt cardiac conditions imposed a substantially higher risk. Adjusti ng for other relevant conditions, heart failure was associated with a 4.5- and 5.9-fold risk, and valvular heart disease a 1.8- and 3.4-fold risk for AF in men and women, respectively. Myocardial infarction sig nificantly increased the risk factor-adjusted likelihood of AF by 40% in men only. Echocardiographic predictors of nonrheumatic AF include l eft atrial enlargement (39% increase in risk per 5-mm increment), left ventricular fractional shortening (34% per 5% decrement), and left ve ntricular wall thickness (28% per 4-mm increment). These echocardiogra phic features offer prognostic information for AF beyond the tradition al clinical risk factors. Electrocardiographic left ventricular hypert rophy increased risk of AF 3-4-fold after adjusting only for age, but this risk ratio is decreased to 1.4 after adjustment for the of her as sociated conditions. The chief hazard of AF is stroke, the risk of whi ch is increased 4-5-fold. Because of its high prevalence in advanced a ge, AF assumes great importance as a risk factor for stroke and by the ninth decade becomes a dominant factor. The attributable risk far str oke associated with AF increases steeply from 1.5% at age 50-59 years to 23.5% at age 80-89 years. AF is associated with a doubling of morta lity in both sexes, which is decreased to 1.5-1.9-fold after adjusting for associated cardiovascular conditions. Decreased survival associat ed with AF occurs across a wide range of ages. (C) 1998 by Excerpta Me dica, Inc.