Temporal trends and patterns in atrial fibrillation incidence: a population-based study of 3.4 million individuals
Authors: Wu J , Nadarajah R , Nakao Y , Nakao K , Wilkinson C , Raveendra K , Mamas M A , Camm A J , Gale C P 
Published: October 2022

Abstract

Background
Atrial fibrillation (AF) is the most common sustained cardiac arrhythmia worldwide; confers an increased risk of adverse outcomes and once diagnosed most patients will require lifelong-treatment. Population-based studies of AF incidence are needed to inform health-service planning. However, few reports refer to a standard population and estimates of incidence in high income countries vary by over 12-fold.

Purpose
We aimed to assess trends in the crude and standardised atrial fibrillation incidence by sex, age, socioeconomic status and region in a large general population cohort from England. We also investigated the comorbidity profile of patients over almost two decades.

Methods
We used linked primary and secondary electronic health records of 3.4 million individuals from the Clinical Practice Research Datalink (CPRD). The CPRD database contains anonymised patient data from approximately 7% of the UK population and is broadly representative in terms of age, sex, and ethnicity. Eligible patients aged 16 years and older contributed data between Jan 1 1998 and Dec 31 2017. We defined incident AF diagnosis as the first record of AF in primary care or hospital admission records from any diagnostic position. For incidence calculations, we excluded all individuals who had a diagnosis of AF before the study start date, or within the first 12 months of registration with their general practice. For patients with incident AF, we extracted baseline characteristics, comorbidities, socioeconomic status and geographic region. We calculated standardised rates by applying direct age and sex standardisation to the 2013 European Standard Population. We inferred crude rates by applying year-specific, age-specific and sex-specific incidence to UK census mid-year population estimates.

Results
From 1998 to 2017 AF incidence (standardised by age and sex) increased by 30% (from 247 to 322 per 100,000 person-years; adjusted incidence ratio [IRR] 1.30, 95% CI 1.27–1.33) (Figure 1). Absolute number of incident AF increased by 72% (from 117,880 in 1998 to 202,333 in 2017), due to an increasing number of older people. Comorbidity burden at diagnosis of AF increased (2.58 [SD 1.83] vs 3.74 [2.29] conditions; adjusted difference 1.26, 95% CI 1.14–1.39). Age-standardised incidence was higher in men than women (IRR 1.49; 95% CI 1.46–1.52), and men were younger at diagnosis (adjusted difference 5.53 years; 95% CI 5.36–5.69). Socioeconomically deprived individuals had more comorbidities and were more likely to develop AF than the most affluent individuals (IRR 1.20; 95% CI 1.15–1.24). Over time, the age of AF diagnosis declined disproportionately in the most deprived individuals (Figure 2).

Conclusion
In England AF incidence has increased, and the socioeconomic gradient in age at diagnosis and comorbidity burden widened. This changing burden of AF requires policy-based interventions to prevent associated morbidity and mortality.

Funding Acknowledgement
Type of funding sources: Foundation. Main funding source(s): British Heart Foundation, National Institute of Health Research