Factors Associated With the Epidemic of Hospitalizations Due to Atrial Fibrillation.

Abstract

Recent reports have described that hospitalizations for atrial fibrillation (AF) are continuing to increase. Given that hospitalizations are responsible for most of the economic burden associated with AF, the aim of this study was to characterize the impact of age and how changing procedural practices may be contributing to the increasing rates of AF hospitalizations. The annual age- and gender-specific incidence of hospitalizations for AF, electrical cardioversions, electrophysiologic studies, and radiofrequency ablation procedures in Australia were determined from 1993 to 2007 inclusive. Over this 15-year follow-up period spanning almost 300 million person-years, a total of 473,501 hospitalizations for AF were identified. There was a relative increase in AF hospitalizations of 203% over the study period, in contrast to an increase for all hospitalizations of only 71%. Whereas the gender-specific incidence of hospitalizations remained stable, the age-specific incidence increased significantly over the study period, particularly in older age groups. AF hospitalizations associated with electrical cardioversions decreased from 27% to 14% over the study period. Electrophysiologic studies and radiofrequency ablation procedures contributed minimally to the overall increase in AF hospitalizations observed. In conclusion, in addition to the growing prevalence of AF because of the aging population, there is an increasing age-specific incidence of hospitalizations for AF, particularly in older age groups. In contrast, changing procedural trends have contributed minimally to the increasing number of AF-associated hospitalizations. Greater attention to older patients with AF is required to develop strategies to prevent hospitalizations and contain the growing burden on health care systems.

Full text

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Factors Associated With the Epidemic of Hospitalizations
Due to Atrial Fibrillation
Christopher X. Wong, MBBS*, Anthony G. Brooks, PhD, Dennis H. Lau, MBBS, PhD,
Darryl P. Leong, MBBS, MPH, PhD, Michelle T. Sun, Thomas Sullivan, BMaCompSci(Hons),
Kurt C. Roberts-Thomson, MBBS, PhD, and Prashanthan Sanders, MBBS, PhD
Recent reports have described that hospitalizations for atrial fibrillation (AF) are continu-
ing to increase. Given that hospitalizations are responsible for most of the economic burden
associated with AF, the aim of this study was to characterize the impact of age and how
changing procedural practices may be contributing to the increasing rates of AF hospital-
izations. The annual age- and gender-specific incidence of hospitalizations for AF, electri-
cal cardioversions, electrophysiologic studies, and radiofrequency ablation procedures in
Australia were determined from 1993 to 2007 inclusive. Over this 15-year follow-up period
spanning almost 300 million person-years, a total of 473,501 hospitalizations for AF were
identified. There was a relative increase in AF hospitalizations of 203% over the study
period, in contrast to an increase for all hospitalizations of only 71%. Whereas the
gender-specific incidence of hospitalizations remained stable, the age-specific incidence
increased significantly over the study period, particularly in older age groups. AF hospi-
talizations associated with electrical cardioversions decreased from 27% to 14% over the
study period. Electrophysiologic studies and radiofrequency ablation procedures contributed
minimally to the overall increase in AF hospitalizations observed. In conclusion, in addition to
the growing prevalence of AF because of the aging population, there is an increasing age-
specific incidence of hospitalizations for AF, particularly in older age groups. In contrast,
changing procedural trends have contributed minimally to the increasing number of AF-
associated hospitalizations. Greater attention to older patients with AF is required to develop
strategies to prevent hospitalizations and contain the growing burden on health care
systems.© 2012 Elsevier Inc. All rights reserved. (Am J Cardiol 2012;110:1496–1499)
A number of studies have suggested that the prevalence
of atrial fibrillation (AF) and subsequent utilization of
health care services are increasing.1–12From a sample of
hospitals in the United States, it has been estimated that
hospitalizations for AF increased twofold to threefold from
1985 to 1999 and that these have been increasing more so
than for any other heart rhythm disorder.3,13European re-
ports have likewise shown dramatic increases in the hospi-
talizations for AF, with Scotland also demonstrating a two-
fold to threefold increase between 1986 and 1996.4,5,9
Because most of the economic cost associated with AF is
borne by hospital systems, the factors driving these trends
are of paramount public health and clinical importance.14–16
We sought to explore how age and evolving interventional
procedures might be contributing to the increasing rate of
hospitalizations for AF.
Methods
Data were obtained from the National Hospital Morbid-
ity Dataset, a source maintained by the Australian Institute
of Health and Welfare that includes inpatient information at
every hospital in Australia. The proportion of missing data
is negligible, representing ?0.004% of cases per year.
We identified hospitalizations with principal diagnoses
of AF across a 15-year period from 1993 through 2007
inclusive. The International Classification of Diseases,
Ninth Revision, Clinical Modification, and International
Classification of Diseases, Tenth Revision, Australian Mod-
ification, were used for coding hospitalization diagnoses
from 1993 to 1997 and from 1998 to 2007 respectively.
Codes were derived from physicians’ diagnoses by trained
clinical coders. AF was defined for patients with Interna-
Centre for Heart Rhythm Disorders, University of Adelaide and the
Royal Adelaide Hospital, Adelaide, Australia. Manuscript received May
24, 2012; revised manuscript received and accepted July 4, 2012.
Dr. Wong is supported by a Rhodes Scholarship from the Rhodes Trust.
Drs. Brooks, Roberts-Thomson, and Sanders are supported by the National
Heart Foundation of Australia. Drs. Lau and Leong are supported by a
postdoctoral fellowship from the National Health and Medical Research
Council of Australia. Dr. Leong is supported by the National Heart Foun-
dation of Australia and the Royal Australasian College of Physicians.
Dr. Roberts-Thomson has served on the advisory board of St. Jude
Medical, St. Paul, Minnesota. Dr. Sanders has served on the advisory board
of St. Jude Medical; Bard Electrophysiology, Lowell, Massachusetts; Bio-
sense Webster, Diamond Bar, California; Medtronic, Minneapolis, Minne-
sota; Sanofi-Aventis, Paris, France; and Merck, Whitehouse Station, New
Jersey. Dr. Sanders has received lecture fees from St. Jude Medical, Bard
Electrophysiology, Biosense Webster, Medtronic, and Merck. Dr. Sanders
has received research funding from St. Jude Medical, Bard Electrophysi-
ology, Biosense Webster, and Medtronic.
This study was presented in part at the European Society of Cardiology
Congress, Stockholm, Sweden, August 2010 and published in abstract form
(Eur Heart J 2010;31:S166).
*Corresponding author: Tel: 61-8-8222-2723; fax: 61-8-8222-2722.
E-mail address: c.wong@adelaide.edu.au (C.X. Wong).
0002-9149/12/$ – see front matter © 2012 Elsevier Inc. All rights reserved.
http://dx.doi.org/10.1016/j.amjcard.2012.07.011
www.ajconline.org

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tional Classification of Diseases, Ninth Revision, Clinical
Modification, code 4273, and International Classification of
Diseases, Tenth Revision, Australian Modification, code
I48, codes that include AF and atrial flutter. We also cal-
culated the total number of all hospitalizations for any
diagnosis to characterize the relative burden of AF. Hospi-
talization data are presented for the number of hospitaliza-
tions, age grouping, length of stay, and total hospital bed
utilization. We report data in age groupings of ?50, 50 to
59, 60 to 69, 70 to 79, and ?80 years. The prevalence of
hospitalizations are expressed as the number per 10,000
population, and midyear population estimates were sourced
from the Australian Bureau of Statistics.17
To ascertain the impact of procedures on hospitalization
trends for these conditions, we evaluated trends in direct-
current electrical cardioversion, electrophysiologic studies, and
radiofrequency ablation procedures to provide further insight
into the factors driving AF hospitalizations. Data for electrical
cardioversions, electrophysiologic studies, and radiofrequency
ablation procedures were available from 2000. Given that data
for radiofrequency ablation procedures were only available
separatelyfromotherelectrophysiologicstudiesfrom2004,we
studied trends in these procedures separately; electrophysi-
ologic studies were analyzed from 2000 to 2003 and radiofre-
quency ablation procedures from 2004 to 2007.
Time trends in the yearly number of hospitalizations
were assessed using negative binomial regression models.
Comparisons were made within and between conditions and
by age group and gender. Time trends in the yearly preva-
lence of hospitalizations, defined as the number of hospi-
talizations in a calendar year divided by midyear population
estimates, were analyzed as described previously but with
the logarithm of the population size included as an offset
variable in the models. Prevalence rates were also investi-
gated by directly standardizing yearly hospitalization counts
to the age and gender structure of the Australian population
in 2007. Finally, time trends in length of stay and bed days
used were assessed using negative binomial regression
models. All analyses were performed using SAS version 9.2
(SAS Institute Inc., Cary, North Carolina), and statistical
significance was set at p ?0.05.
Results
Over a 15-year period from 1993 to 2007, there were a
total of 93,029,656 hospitalizations for any diagnosis in
Australia (representing a follow-up period of almost 300
million person-years). There were a total of 473,501 hospi-
talizations for AF. There was a relative increase of 203% in
the number of AF hospitalizations (7.9% annually, rate ratio
[RR] 1.079, 95% confidence interval [CI] 1.069 to 1.088,
p ?0.001; Table 1). This was in contrast to a relative
increase in the number of all hospitalizations of only 71% or
an estimated 3.7% per year (RR 1.037, 95% CI 1.036 to
1.039, p ?0.001). As a result, AF as a percentage of all
hospitalizations increased by an estimated 4.0% per year
(RR 1.040, 95% CI 1.031 to 1.050, p ?0.001; Figure 1).
These trends were additionally associated with a decrease
in average length of stay (1.8% annually, RR 0.982, 95%
CI 0.978 to 0.987, p ?0.001) and an increase in total bed
Table 1
Table showing the number of hospitalizations, incidence of hospitalizations, average length of stay and total bed days used from 1993 to 2007 in Australia.
Year Number of
Hospitalizations
Incidence of Hospitalizations
(per 10,000 Population)
Average Length
of Stay (days)
Total Bed Days
Used (days)
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
Relative increase, 1993–2007* (%)
15,555
17,995
19,601
22,055
25,096
27,245
31,109
32,248
36,156
36,654
36,191
38,286
41,510
45,618
47,164
203.2
8.8
10.1
10.9
12.0
13.6
14.6
16.4
17.4
18.6
18.6
18.2
19.0
20.4
22.0
22.4
155.0
4.2
4.0
3.8
3.6
3.5
3.3
3.2
3.1
3.1
3.3
3.3
3.2
3.2
3.2
3.1
64,608
71,367
74,496
80,263
87,536
90,520
99,867
104,152
112,984
119,285
117,723
122,193
134,405
144,476
145,200
?26.2124.7
* Calculated as (2007 value ? 1993 value)/1993 value ? 100.
Figure 1. Relative burden of AF hospitalizations as a percentage of total
hospitalizations from 1993 to 2007 inclusive.
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days used (5.9% annually, RR 1.059, 95% CI 1.055 to
1.063, p ?0.001).
The proportions of AF hospitalizations for men and
women were relatively steady over the study period, with
men accounting for an average of 54.8% of hospitalizations
and women for an average of 45.2%. Figure 2 shows the
age- and gender-specific incidence of hospitalizations for
AF from 1993 to 2007. The incidence of hospitalizations
was higher in older age groups for every year. The propor-
tion of patients hospitalized with AF and aged ?80 years
increased from 10% to 16% in men and from 25% to 34%
in women.
From 2000 to 2007, the percentage of AF hospitaliza-
tions for which electrical cardioversion was used decreased
from 27% to 14%. Trends in electrophysiologic studies from
2000 to 2003 and radiofrequency ablation procedures from
2004 to 2007 were similarly analyzed as a percentage of all
AF hospitalizations respectively. From 2000 to 2003, elec-
trophysiologic studies as a percentage of AF hospitaliza-
tions increased from 15% to 17%. From 2004 to 2007,
radiofrequency ablation procedures as a percentage of AF
hospitalizations increased from 9% to 11%.
Discussion
We examined nationwide trends in hospitalizations for
AF in Australia over a 15-year period to determine factors
that might be contributing to the increasing rates of hospi-
talizations for this prolific condition. Our findings highlight
that the age-specific incidence of hospitalizations for AF is
continuing to increase. Not only are aging population struc-
tures resulting in a growing prevalence of AF, but elderly
patients in particular are being hospitalized for AF at an
increasing rate. Our data additionally suggest that AF-re-
lated procedures, such as electrical cardioversions, electro-
physiologic studies, and radiofrequency ablation proce-
dures, were unlikely to have contributed significantly to the
increasing rates of AF hospitalizations.
Recent reports have highlighted the increasing public
health burden of AF.2,11Importantly, it has been recognized
that hospitalizations account for most of the cost associated
with AF.14,15,18,19A Scottish study on AF-related hospital
activity found that from 1986 to 1996, the number of AF
hospitalizations had increased threefold, from 1,869 to
5,757.4This was accompanied by an 80% increase in bed
days used, despite a decreasing median length of stay (from
6 to 3 days). An analysis of Danish data additionally re-
vealed that hospitalizations had increased by 60% over a
similar period, from 163 to 216 cases.7Another study used
survey data to estimate hospitalizations in the entire United
States.13From 1985 to 1999, these investigators estimated
that hospitalizations for AF had increased from 154,086 to
376,487.13Similarly, Canadian investigators have also de-
scribed an increase in hospitalizations from 1997 to 2000.6
Despite the limitations of representative data and modest-
sized cohorts, these studies highlighted a growing clinical
and public health problem.
Given the increasing prevalence of AF with age, the
aging population structures seen in developed countries
around the world are clearly in part responsible for the
increasing number of hospitalizations for AF. In addition to
this, however, our data highlight that the age-specific inci-
dence of hospitalizations for AF is also increasing. The
reasons for this are multifactorial, but improving medical
care in recent years has resulted in patients’ having more
prolonged exposure to traditional and newer risk factors,
such as obesity and obstructive sleep apnea; this exposure is
likely to be contributing significantly to the increasing in-
cidence and resultant hospitalizations for AF.20–23
Other investigators have suggested that emerging inter-
ventional procedures may have accounted for part of the
recent trends.19,24,25We were unable to link procedural data
with AF hospitalizations in our study. However, when pro-
cedures were considered as a percentage of AF hospitaliza-
tions (a conservative approach given many of these would
Figure 2. Separate graphs showing age- and gender-specific prevalence of hospitalizations for AF from 1993 to 2007 inclusive.
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Page 4

have been for other arrhythmias), they would have ac-
counted for an increasing but very small proportion of AF
hospitalizations. A previous report also noted that major
“rate versus rhythm” trials were followed by a slowing in
AF hospitalizations in the United States and a decrease in
cardioversions.19Our finding that cardioversions were as-
sociated with a significantly smaller proportion of AF hos-
pitalizations in Australia confirms that rhythm control with
cardioversion is no longer used as frequently. Thus, the
observed increases in total AF hospitalizations occurring
despite a decrease in AF hospitalizations for cardioversions
are even more striking.
The growing AF hospitalizations show no sign of abating
and in the context of the aging population represent a
staggering economic burden. Hospitalizations have repeat-
edly been confirmed as the major cost driver associated with
AF.14–16,18Health care planning and practitioner education
are warranted to ensure that efficacious and cost-effective
management strategies are used to minimize the risk for
hospitalization in patients with AF, particularly in older age
groups. Greater attention on primary prevention strategies
will also be required to contain this growing epidemic.
Similar to other retrospective analyses using administra-
tive coding data, there were a number of limitations. It was
not possible to determine whether cases were de novo or
repeat hospitalizations. Although each hospitalization still
represents additional burden on the health care system, this
information may have provided insights into potential strat-
egies to reduce repeat hospitalizations. Similarly, hospital
demographic information was not available; such data may
have provided further insights into the factors driving hos-
pitalizations. Previous investigators have speculated that
increasing hospitalizations for AF may be due in part to
changes in admission thresholds and increases in related
procedures.4In our study, not all procedures were able to be
linked with an AF hospitalization. However, our conserva-
tive approach, assuming that all procedures were associated
with AF, suggested that they constitute a small percentage
of total AF hospitalizations. An increased awareness of AF
could certainly have influenced physician practice and ex-
plain the observed trends in part by reducing admission
thresholds rather than reflecting true increases in preva-
lence. It should be pointed out, however, that if this is the
case, the true prevalence of may have been substantially
underestimated in the past. Furthermore, from a health sys-
tem perspective, the increasing hospitalizations still repre-
sent a significant economic burden regardless of potentially
changing admission reasons.
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