The Increasing Burden of Atrial Fibrillation Compared With Heart Failure and Myocardial Infarction: A 15-Year Study of All Hospitalizations in Australia FREE

In recent years, reports have suggested that the incidence of atrial fibrillation (AF) is increasing.¹ Importantly, it has been recognized that hospitalizations account for the majority of the economic cost associated with AF.² Trends in hospitalizations for this common condition have shown 2- to 3-fold increases in both North America and Europe through the 1980s and 1990s.^3- 5 Despite the limitations of representative data and modest-sized cohorts, these reports highlight a growing clinical and public health problem.

It is not known whether these increasing trends have continued in recent years and whether they are occurring elsewhere outside North American and Europe. The present study thus examined nationwide trends in AF hospitalizations across the entirety of Australia over a 15-year period (a follow-up period of almost 300 million person-years). In addition, we sought to contrast them with that of 2 other common cardiovascular conditions, myocardial infarction (MI) and heart failure (HF).

Data were obtained from the National Hospital Morbidity Data set, a source maintained by the Australian Institute of Health and Welfare that includes inpatient information at every hospital in Australia. We identified hospitalizations with a principal diagnosis of AF, MI, and HF from 1993 through 2007. Atrial fibrillation was defined for patients with International Classification of Diseases, Ninth Revision, Clinical Modification code 4273, and International Statistical Classification of Diseases and Related Health Problems, Tenth Revision, Australian Modification (ICD-10-AM) code I48. Myocardial infarction was defined for patients with ICD-9-CM code 410 and ICD-10-AM code I21. Heart failure was defined for patients with ICD-9-CM code 428 and ICD-10-AM code I50. Australian Bureau of Statistics population estimates were used to calculate hospitalization prevalence. Statistical analyses were performed using SAS version 9.2 software (SAS Institute Inc).

We identified a total of 473 501 AF hospitalizations, 208 305 MI hospitalizations, and 622 082 HF hospitalizations (Figure). There was an increase in the number of hospitalizations for AF of 203% (7.9% annually; rate ratio [RR], 1.079 [95% CI, 1.069-1.088]; P < .001). In contrast, the number of hospitalizations for MI and HF only demonstrated increases of 79% and 17%, or 4.5% (RR, 1.045 [95% CI, 1.040-1.050]; P < .001) and 0.7% (RR, 1.007 [95% CI, 1.004-1.009]; P < .001) annually, respectively (P < .001 for both compared with AF).

The prevalence of AF hospitalizations increased by 155% (6.5% annually; RR, 1.065 [95% CI, 1.056-1.075]; P < .001). The prevalence of MI hospitalizations only increased by 50% (3.2% annually; RR, 1.032 [95% CI, 1.027-1.037]; P < .001), and the prevalence of HF hospitalizations decreased by 2% (3.0% annually; RR, 0.970 [95% CI, 0.968-0.973]; P < .001). Though the prevalence of hospitalizations for HF showed a noticeable decline in both sexes and all age groups (P < .001 for all), the prevalence of hospitalizations for AF and MI increased in both sexes and all age groups (P < .001 for both).

While the mean length of stay for AF, MI, and HF hospitalizations fell (4.0 to 3.1 days, 8.2 to 5.4 days, and 10.4 to 7.8 days, respectively), there was a 125% increase in the total bed-days used for AF hospitalizations (5.9% annually; RR, 1.059 [95% CI, 1.055-1.063]; P < .001); in contrast, there was only an 18% increase (1.7% annually; RR, 1.017 [95% CI, 1.010-1.024]; P < .001), and a 15% decrease (1.1% annually; RR, 0.989 [95% CI, 0.985-0.993]; P < .001) in bed-days for MI and HF, respectively.

Over a 15-year period from 1993 through 2007 in Australia, we showed that the number of hospitalizations for AF nationwide had increased significantly compared with MI and HF. These differences were even more pronounced when the prevalence of these hospitalizations were examined. Furthermore, despite similar decreases in length of stay for all 3 conditions, there was a striking increase in the number of bed-days used for AF.

Our nationwide findings confirm previous reports using representative data that the epidemic of AF is continuing exponentially.^3- 5 It also highlights that the number of resultant hospitalizations has shown no sign of abating in recent years. Furthermore, comparing AF trends with that of 2 other common cardiovascular conditions puts the clinical and public health importance of these trends in context. While previous reports suggested that HF once accounted for twice as many hospitalizations,⁴ AF hospitalizations have since surpassed that for HF and are approaching that for MI.

A number of reasons are likely to be contributing to the rise in AF hospitalizations. The aging population is certainly in part responsible for these AF trends, though our data show that the age-specific prevalence is also increasing. Improving medical care has also resulted in individuals having a more prolonged exposure to traditional and newer risk factors for AF, such as obesity and obstructive sleep apnea.^6- 9

In conclusion, to our knowledge, this is the first report on nationwide trend in hospitalizations for AF outside North American and Europe. The public health burden of AF is enormous and is continuing to increase at a rate greater than that of other common cardiovascular conditions. These findings have important implications for health care planning and the need for better primary prevention and treatment of AF.