Elsevier

The Lancet

Volume 386, Issue 9989, 11–17 July 2015, Pages 154-162
The Lancet

Articles
50 year trends in atrial fibrillation prevalence, incidence, risk factors, and mortality in the Framingham Heart Study: a cohort study

https://doi.org/10.1016/S0140-6736(14)61774-8Get rights and content

Summary

Background

Comprehensive long-term data on atrial fibrillation trends in men and women are scant. We aimed to provide such data through analysis of the Framingham cohort over 50 years.

Methods

We investigated trends in incidence, prevalence, and risk factors for atrial fibrillation and its association with stroke and mortality after onset in 9511 participants enrolled in the Framingham Heart Study between 1958 and 2007. We analysed trends within 10 year groups (1958–67, 1968–77, 1978–87, 1988–97, and 1998–2007), stratified by sex.

Findings

During 50 years of observation (202 417 person-years), 1544 cases of new-onset atrial fibrillation occurred (of whom 723 [47%] were women). Between 1958–67 and 1998–2007, age-adjusted prevalence of atrial fibrillation quadrupled from 20·4 to 96·2 cases per 1000 person-years in men and from 13·7 to 49·4 cases per 1000 person-years in women; age-adjusted incidence increased from 3·7 to 13·4 new cases per 1000 person-years in men and from 2·5 to 8·6 new cases per 1000 person-years in women (ptrend<0·0001 for all comparisons). For atrial fibrillation diagnosed by electrocardiograph (ECG) during routine Framingham examinations, age-adjusted prevalence per 1000 person-years increased (12·6 in 1958–67 to 25·7 in 1998–2007 in men, ptrend=0·0007; 8·1 to 11·8 in women, ptrend=0·009). However, age-adjusted incidence of atrial fibrillation by Framingham Heart Study ECGs did not change significantly with time. Although the prevalence of most risk factors changed over time, their associated hazards for atrial fibrillation changed little. Multivariable-adjusted proportional hazards models revealed a 74% (95% CI 50–86%) decrease in stroke (hazards ratio [HR] 3·77, 95% CI 1·98–7·20 in 1958–1967 compared with 1998–2007; ptrend=0·0001) and a 25% (95% CI −3–46%) decrease in mortality (HR 1·34, 95% CI 0·97–1·86 in 1958–1967 compared with 1998–2007; ptrend=0·003) in 20 years following atrial fibrillation onset.

Interpretation

Trends of increased incidence and prevalence of atrial fibrillation in the community were probably partly due to enhanced surveillance. Measures are needed to enhance early detection of atrial fibrillation, through increased awareness coupled with targeted screening programmes and risk factor-specific prevention.

Funding

NIH, NHLBI, NINDS, Deutsche Forschungsgemeinschaft.

Introduction

With ageing populations, atrial fibrillation was predicted to affect 6–12 million people in the USA by 2050 and 17·9 million in Europe by 2060.1, 2, 3 Atrial fibrillation is a major public health problem with high comorbidity,4 increased mortality risk,5 and soaring health-care costs.6 The reasons for the increase in the prevalence of atrial fibrillation is incompletely understood7, 8 but might be related to enhanced detection, rising incidence, improved survival in patients with cardiovascular conditions that predispose to atrial fibrillation, and greater survival after onset of atrial fibrillation.9 Many previous studies of trends in atrial fibrillation were based on administrative or hospital databases, which might be subject to ascertainment biases. Evidence1, 2, 7, 8, 9 for an increase in prevalence and reduced mortality after onset of atrial fibrillation exists. Results of some administrative data1, 8 suggest that the incidence of atrial fibrillation is increasing, whereas results of other investigations10, 11 show that the incidence and prevalence of atrial fibrillation vary widely. Although trends in the epidemiology of atrial fibrillation have been reported to be similar in direction for both sexes, the exact estimates have differed by sex, with higher prevalence in men and variable incidence estimates in women.1, 8

Increased awareness of atrial fibrillation and use of routine electrocardiographs (ECG) and extended electrocardiographic monitoring devices enhance the detection of atrial fibrillation, and thereby might identify more cases in the community, thus increasing incidence and prevalence because of enhanced surveillance.

Long-term trends for atrial fibrillation prevalence, incidence, risk factors, and for stroke and mortality after the onset of atrial fibrillation in community-based cohorts have not been investigated systematically. With routine assessment of atrial fibrillation and its risk factors, as well as cardiovascular outcomes over the course of 50 years, the Framingham Heart Study is a unique resource to monitor long-term trends in prevalence and incidence, risk factors, and outcomes of atrial fibrillation in the community and might provide insights to guide future prevention strategies.

Section snippets

Study design and participants

The Framingham Heart Study began in 1948 with enrolment of the original cohort (5209 participants).12 The offspring cohort (5124 participants) was enrolled in the early 1970s and comprised adult children of original cohort participants and their spouses.13 Individuals who were aged 50–89 years at the beginning of follow-up were eligible for analyses (4420 individuals from the original cohort and 5091 from the offspring cohort). Due to small numbers, we did not include atrial fibrillation cases

Results

The 50 year observation period extended from 1958 to 2007 and comprised 202 417 person-years of follow-up, during which 1544 individuals (821 men, 723 women) had new-onset atrial fibrillation, ascertained from routine Framingham clinic visits and outside medical records. Examination of atrial fibrillation ascertained from all sources indicated about a quadruple increase in age-adjusted period prevalence from 1958–67 to 1998–2007 (table 1). Similarly, the age-adjusted incidence of atrial

Discussion

Over the course of 50 years of observation of a community-based sample, we observed an increasing prevalence and incidence of atrial fibrillation accompanied by improved survival and reduced risk of stroke after onset of atrial fibrillation (panel). When we restricted our analyses to atrial fibrillation cases detected by ECG at routine Framingham Heart Study clinic visits (ie, uniform ascertainment), the increase in prevalence of atrial fibrillation persisted, but the trend in age-adjusted

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