30-year nationwide trends in incidence of atrial fibrillation in Denmark and associated 5-year risk of heart failure, stroke, and death

Abstract

Background

Long-term nationwide trends in atrial fibrillation (AF) incidence and 5-year outcomes are rare.

Methods

We conducted a population-based cohort study using the Danish National Patient Registry covering all Danish hospitals. We computed standardized incidence rates during 1983–2012. We used Cox regression to estimate hazard ratios (HRs) of heart failure, stroke, and death within 5 years, comparing 5-year calendar periods with the earliest period (1983–1987) as reference.

Results

We identified 312,420 patients with first-time hospital-diagnosed AF. The incidence rate per 100,000 person-years increased from 98 in 1983 to 307 in 2012. The mean annual increase during the 30-year study period was 4%, with a 6% increase annually until 2000 and a 1.4% increase annually thereafter. The incidence trends were most pronounced among men and persons above 70 years. Among high-risk subgroups, AF incidence was consistently highest in patients with valvular heart disease or heart failure. The rate of heart failure following AF declined by 50% over the entire study period (HR: 0.49, 95% confidence interval (CI): 0.48–0.51) and the mortality rate declined by 40% (HR: 0.62, 95% CI: 0.61–0.63). Within the last two decades, the rate for ischemic stroke declined by 20% (HR 0.81, 95% CI: 0.78–0.84), but increased almost as much for haemorrhagic stroke (HR: 1.14, 95% CI: 1.01–1.29).

Conclusions

The long-term risk of heart failure, ischemic stroke, and death following onset of AF has decreased remarkably over the last three decades. Still, the threefold increased incidence of hospital-diagnosed AF during the same period is a major public health concern.

Introduction

Atrial fibrillation (AF) is the most common cardiac arrhythmia observed in clinical practice. Its prevalence in the European population over age 55 years is projected to double by 2060 [1]. Well-established risk factors include age, male sex, heart failure, valvular heart disease, myocardial infarction, hypertension, hypertrophic cardiomyopathy, cardiac surgery, diabetes mellitus, inflammation, and hyperthyroidism [2]. As AF is associated with reduced quality of life [3], morbidities (particularly embolic stroke [4] and heart failure [5]), and mortality [6], the increasing number of patients with AF has major public health implications and associated costs [7].

Although AF incidence and outcomes have been examined in community-based cohorts, such as the Rotterdam [1], [8], Copenhagen Heart [9], and Framingham Heart studies [10], long-term trends in AF incidence and 5-year outcomes remain to be investigated in nationwide settings. To provide updated long-term statistics in an era of changing anticoagulant therapies [11], we linked complete hospital, migration, and mortality data at the individual level to examine 30-year trends in incidence of diagnosed AF and associated 5-year risks of heart failure, stroke, and death in Denmark.