ABSTRACT

The purpose of the PhD dissertation was to analyse 1) the temporal changes in the population prevalence of atrial fibrillation (AF), 2) the temporal changes in hospital admission rates for AF, and 3) the impact of AF on the risk of stroke.

The dissertation is based on data from the Copenhagen City Heart Study. This is a population-based cohort study started in the mid 1970s, including an initial random population sample of nearly 20,000 people. Since the first examination in 1976-1978, the cohort has been reinvited to two additional examinations in 1981-1983 and in 1991-1994. A total of 17,826 individuals participated in one or more of the three examinations, and overall 37,056 person examinations have been performed. At the three examinations, each participant filled in a questionnaire concerning their medical history and underwent a physical examination program that included an ECG.

Prevalence: In men aged 50-89 years, the age-adjusted prevalence of AF, determined from ECGs, increased from 1.4% in 1976-1978 to 1.9% in 1981-1983 and further to 3.3% in 1991-1994. The increase was highly significant (p<0.01, adjusted for age). During the same period, the prevalence of AF in women remained largely constant at 1.5% in 1976-1978, 1.0% in 1981-1983 and 1.1% in 1991-1994 (p = 0.20, adjusted for age). After multivariate adjustment for co-morbidity, the increase in the prevalence of AF in men persisted. The reason for this gender-specific increase in the prevalence of AF is unknown.

Hospital admission: From the 1980s to the 1990s, a 60% increase in the rate of first hospital admission for AF was observed in men as well as in women without previous AF. The increase in the rate of admissions for AF was observed across all age groups and was independent of concomitant changes in co-morbidity, height, weight and smoking status. This increase may result from an increased focus on the arrhythmia leading to a shift in admission threshold or it may reflect a true population increase in the incidence of AF.

Stroke risk: AF was found to be an independent risk factor for stroke in men and in women, but the risk of stroke imposed by AF was more than 4-fold greater in women than in men. The greater impact of AF in women was independent of the presence of other known risk factors for stroke and death.

AF is a frequent arrhythmia with a substantial impact on the risk of stroke. For reasons yet unclear, there has been an age-independent increase in the prevalence of AF in the male population and the number of hospitalisations for AF has increased in both sexes. Due to the ageing of the population, a considerable age-dependent increase in the prevalence of AF during the next decades must be anticipated. A challenge will be to ensure proper stroke risk assessment and appropriate antithrombotic prophylaxis in the rising number of subjects with AF.