Original article
Incidence of chronic atrial fibrillation in general practice and its treatment pattern

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Abstract

The object of this article was to estimate the incidence rate of chronic atrial fibrillation (AF) in a general practice setting, to identify factors predisposing to its occurrence, and to describe treatment patterns in the year following the diagnosis. The method used was a population-based cohort study using the General Practice Research Database (GPRD) in the UK. We identified patients aged 40–89 years with a first ever recorded diagnosis of AF. The diagnosis was validated through a questionnaire sent to the general practitioners. A nested case–control analysis was performed to assess risk factors for AF using 1,035 confirmed incident cases of chronic AF and a random sample of 5,000 controls from the original source population. The incidence rate of chronic AF was 1.7 per 1,000 person-years, and increased markedly with age. The age adjusted rate ratio among males was 1.4 (95% CI 1.2–1.6). The major risk factors were age, high BMI, excessive alcohol consumption, and prior cardiovascular comorbidity, in particular, valvular heart disease and heart failure. Digoxin was used in close to 70% of the patients, and close to 15% did not receive any antiarrhythmic treatment. Close to 40% did not receive either warfarin or aspirin in the 3 months period after the diagnosis. Among the potential candidates for anticoagulation only 22% of those aged 70 years or older were prescribed warfarin in comparison to 49% among patients aged 40–69 years. Chronic AF is a disease of the elderly, with women presenting a lower incidence rate than men specially in young age. Age, weight, excessive alcohol consumption, and cardiovascular morbidity were the main independent risk factors for AF. Less than half of patients with chronic AF and no contraindications for anticoagulation received warfarin within the first trimester after the diagnosis.

Section snippets

Background

Atrial Fibrillation (AF) is the most common chronic arrhythmia, occurring most frequently in the presence of other cardiovascular disease [1], and is now recognized as the most common cardiac disorder leading to systemic emboli [2].

AF incidence and prevalence is known to increase steeply with advancing age. Incidence at age 50 varies between 0.4 and 0.7 per 1,000 person-years, while at the age of 80 it lies between 1 and 2%. The corresponding prevalence goes from 1.1 per 1,000 patients at age

Source population

We performed a retrospective cohort study using data from the General Practice Research Database (GPRD). The source population includes approximately three million residents in the UK registered with general practitioners (GPs), which provide data to the GPRD. The information recorded includes demographics, medical diagnoses, referrals to consultant and hospital, and a register of written prescriptions. In addition, the GP may record laboratory results and other medical data in a free text

Results

The incidence rate of chronic AF was estimated to be 1.7 per 1,000 person-years. The incidence increased markedly with age. We found a rate of 0.05 among patients aged 40 to 49 years, while among patients aged 80–89 this was 8.6 (Fig. 1). Women presented a lower incidence rate than men, specially in young age. The overall age-adjusted relative risk among males was 1.4 (95%CI 1.2–1.6).

Table 1 shows the distribution of health-related characteristics in both cases and controls. Age was the major

Discussion

We observed an overall incidence rate of chronic AF of approximately 3 per 1,000 person-years among patients older than 60 years in the UK, an estimate lower than that reported by other authors in the United States 4, 15. Different methods of case identification and varying operational definitions of AF make comparisons between studies difficult. In the Cardiovascular Heart Study [4], the majority of incident AF patients were identified in the hospital, with only 7% whose AF was still present

Acknowledgements

We thank the staff at EPIC and the participating general practitioners for their collaboration. We also thank the Boston Collaborative Drug Surveillance Program (BCDSP) for providing access to the database. This study was supported by a research grant of AstraZeneca.

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