Prevalence of atrial fibrillation in Asia and the world

Abstract

Atrial fibrillation (AF) is the most common arrhythmia in persons of advanced age, and it is a potent risk factor for cardiogenic ischemic stroke. The overall prevalence of AF is less than 1%, but in people aged 80 years or older the rate is approximately 7–14% in Western countries and 2–3% in Japan. The number of people with AF has been increasing worldwide as the population has aged, and continued increases in the prevalence and incidence of AF are expected with the aging of society. It is predicted that 5–16 million in the United States and more than 1 million in Japan will be affected by 2050. Therefore, AF is one of important diseases that needs to be managed because it is a common disease in aged populations.

Full text

Review
Prevalence of atrial fibrillation in Asia and the world
Eitaro Kodani, MD, PhD
n
, Hirotsugu Atarashi, MD, PhD
Department of Internal Medicine and Cardiology, Nippon Medical School Tama-Nagayama Hospital, 1–7-1 Nagayama, Tama-shi, Tokyo 206-8512, Japan
article info
Article history:
Received 5 April 2012
Received in revised form
4 June 2012
Accepted 2 July 2012
Available online 23 August 2012
Keywords:
Atrial fibrillation
Prevalence
Incidence
Aging
Gender
abstract
Atrial fibrillation (AF) is the most common arrhythmia in persons of advanced age, and it is a potent risk
factor for cardiogenic ischemic stroke. The overall prevalence of AF is less than 1%, but in people aged
80 years or older the rate is approximately 7–14% in Western countries and 2–3% in Japan. The number
of people with AF has been increasing worldwide as the population has aged, and continued increases
in the prevalence and incidence of AF are expected with the aging of society. It is predicted that 5–16
million in the United States and more than 1 million in Japan will be affected by 2050. Therefore, AF is
one of important diseases that needs to be managed because it is a common disease in aged
populations.
&2012 Japanese Heart Rhythm Society. Published by Elsevier B.V. All rights reserved.
Contents
1. Introduction ......................................................................................................330
2. Hospital studies . . . ................................................................................................330
3. Population studies . ................................................................................................331
3.1. Prevalence of AF in the United States and European countries ........................................................331
3.2. Prevalence of AF in Asia. . .....................................................................................333
4. Incidence and projected number of AF cases ............................................................................334
5. Ethnicity and AF. . . ................................................................................................335
6. Epidemiology of AF and future therapeutic strategies . ....................................................................335
7. Concluding remarks ................................................................................................336
Conflict of interest . ................................................................................................336
References .......................................................................................................336
1. Introduction
Atrial fibrillation (AF) is the most common arrhythmia in
elderly people, and it is a potent risk factor for ischemic stroke
associated with cardiogenic thromboembolism and burden of
disability. Therefore, it is important for physicians to be informed
about the prevalence of AF in order to more appropriately assess
and manage patients with AF. Although the prevalence of AF has
been known to be lower in Asia than in Europe and the United
States, the prevalence in Japan has been increasing with aging of
the population, as in Western countries, and a further increase is
expected as the population continues to age.
We herein review the prevalence and the incidence of AF and
summarize previous population- or community-based epidemio-
logical surveys conducted in Western countries and in Asia (Korea
and Japan). The prevalence of AF in medical institutions and the
features of patients who have been diagnosed with AF during
hospital-based studies are also described.
2. Hospital studies
About a half century ago, the frequency of various arrhythmias
detected by electrocardiograms (ECGs) was described by Katz and
Pick in part of ‘‘Clinical Electrocardiography,’’ published in
1956 [1]. The authors analyzed the ECGs of 50,000 consecutive
patients of the Heart Station at Michael Reese Hospital for over
25 years. AF was seen in 5859 patients, for a frequency of 11.7%
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journal homepage: www.elsevier.com/locate/joa
Journal of Arrhythmia
1880-4276/$ - see front matter &2012 Japanese Heart Rhythm Society. Published by Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.joa.2012.07.001
n
Corresponding author. Tel.: þ81 42 371 2111; fax: þ81 42 372 7379.
E-mail address: kodani@nms.ac.jp (E. Kodani).
Journal of Arrhythmia 28 (2012) 330–337

(Table 1)[1]. A similar investigation with 8000 consecutive ECGs
from Tokyo University in Japan was reported in 1971 [2], in which
AF was observed in 538 patients, and the frequency of AF was
6.7%. We also investigated the frequency of arrhythmias and age-
related changes in a general hospital in 1983 [3]. Standard ECGs
were recorded from 5079 consecutive patients aged 15–93 years.
The prevalence of AF was 2.5%, following ventricular premature
complex (3.6%), supraventricular premature complex (3.4%), sinus
tachycardia (3.2%), and first-degree atrioventricular block (2.7%).
In the 1980s, our study showed that the prevalence of AF was
higher in men than in women (2.7% and 2.3%, respectively), which
was confirmed by later epidemiological surveys in Japan and
Western countries. Furthermore, AF was found in 0.58% in
subjects younger than 50 years, 2.5% at ages 50–69 years, and
4.7% at 70 years or older, indicating that the prevalence of AF
increases linearly with age [3].
In the 1990s, several hospital-based surveys were reported. In
a survey of AF among 2686 acute medical admissions to a district
general hospital in Glasgow, UK [4], the prevalence of AF was
6.3%, with the predominant associated medical conditions being
ischemic heart disease, hypertension, and valvular disease.
A similar prospective survey of acute medical admissions over
6 months in West Birmingham, UK, in a multi-ethnic population,
showed a lower prevalence of AF (2.3% in 7451 patients) [5].In
another report from New Zealand in 1999, the prevalence of AF
was 10.4% in 1637 acutely ill patients admitted to the general
medical service at the Auckland Hospital over a 12-week per-
iod [6]. Certain discrepancies between the frequencies of AF
determined by surveys of ECG recordings and those reported in
clinical practice were pointed out in a former report [1]. One of
the reasons proposed was that hospital records were primarily
taken from patients suspected of having cardiac disorders [1].
Other factors include whether the patients were admitted to the
hospital or taken to the outpatient clinic, and whether the
patients were in a general hospital or in a specialized cardiology
unit. The year that the survey was conducted and the age of
participants are also important factors that may contribute to
discrepancies in the prevalence of AF among the surveys.
In 2000, the Hokkaido Atrial Fibrillation Study Group reported
that the prevalence of AF was 14% in 19,825 patients who visited
the cardiovascular clinics of the 13 hospitals in Hokkaido,
Japan [7]. Similarly, according to the Shinken Database 2004,
including 2412 patients who first visited the Cardiovascular
Institute in Tokyo, Japan, AF was found in 286 patients, for a
frequency of 11.8% [8]. These results indicated that the frequency
of AF reported in specialized cardiology units is higher than that
in general hospitals. In the study conducted in Hokkaido [7], the
age-specific prevalence of AF was 3.5% in patients younger than
40 years, 6.9% at ages 40–49 years, 10.4% at 50–59 years, 13.5% at
60–69 years, 18.7% at 70–79 years, and 25.4% in patients who
were 80 years old or older. This trend was similar to that formerly
reported [3], and all the prevalence rates were higher in the
cardiovascular clinics than in the general facilities [3]. In a study
among residents aged 65 years or older at the north end of Kyoto
Prefecture, Japan, in 2006–2007, the prevalence of AF in out-
patients of the community clinic was 10.0%, whereas that found
among residents who had ECGs as part of a annual resident
check-up was 2.1% [9]. Thus, even in the same medical service
area, the prevalence of AF was higher in patients examined in
medical institutions than those examined in health check-up.
The same trend in the age-specific prevalence of AF was observed
in the elderly. It was 6.2% in those aged 65–74 years, 8.6% at
75–84 years, and 11.7% at 85 years or older [9].
3. Population studies
The prevalence of AF in community- or population-based
studies using data from periodic health check-ups may reflect
the state of the general population, including healthy subjects.
Therefore, the characteristics of these individuals may be differ-
ent from those in hospital-based studies.
3.1. Prevalence of AF in the United States and European countries
Table 2 [10] shows the age- and gender-specific prevalence of
AF in the United States and European countries obtained during
previous major epidemiological studies [11–16]. In the first four
population-based surveys conducted during the 1980s and the
1990s, i.e., the Western Australia study [11], the Rochester study
[12], the Framingham study [13], and the Cardiovascular Health
Study [14] that included several thousand subjects, the preva-
lence of AF in the elderly was consistently higher than that in the
younger population (Table 2). Based on these four studies,
Feinberg et al. [17] reported that the prevalence of AF in the
United States in 1991 was 0.89%, and the number of people with
AF was 2.23 million. The prevalence of AF was 2.3% in adults older
than 40 years and was 5.9% in those older than 65 years, again
indicating that the prevalence of AF was increasing with age so
that approximately 70% of those with AF were between 65 and 85
years old (Fig. 1)[17]. In this survey, the prevalence of AF was
highest at the age of 80 years and above, but the number of
people with AF was greatest at the age of 75–79 years (Fig. 1)
[17]. In a report from a general practice research database
including 1.4 million patients registered from general practices
in England and Wales, the prevalence of AF in 1998 was 1.21% in
men and 1.27% in women [15]. The prevalence in elderly indivi-
duals was very high, with a rate over 10% in both men and
Table 1
Frequency of various rhythms in electrocardiograms of 50,000 consecutive
patients.
Arrhythmias Number Frequency (%)
Sinus tachycardia 9340 18.7
Sinus bradycardia 2885 5.8
Sinus arrhythmia 8302 16.6
Wandering pacemaker 1284 2.6
Nodal escape 1062 2.1
Nodal rhythm 502 1.0
Idioventricular pacemaker 233 0.47
Premature systoles 7136 14.3
Atrial 2836 5.7
AV nodal 555 1.1
Ventricular 3476 7.0
Paroxysmal tachycardia 751 1.5
Supraventricular 671 1.3
Ventricular 80 0.16
Atrial fibrillation 5859 11.7
Paroxysmal 1543 3.1
Chronic 4316 8.6
Atrial flutter 270 0.54
AV dissociation 681 1.4
SA block 114 0.23
AV block 2058 4.1
First degree 1480 3.0
Second degree 345 0.69
Third degree 233 0.47
Bigeminy 621 1.24
Parasystole 153 0.31
Recipient rhythm 40 0.08
WPW syndrome 81 0.16
Cited from Katz and Pick [1].
E. Kodani, H. Atarashi / Journal of Arrhythmia 28 (2012) 330–337 331

women, and the number of people with AF was greatest at the age
of 75–84 years [15].
The AnTicoagulation and Risk Factors in Atrial Fibrillation
(ATRIA) study, which included 1.89 million adults aged 20 years
or older who enrolled in a large Health Maintenance Organization
(HMO) in California, was reported from the United States in 2001
[16]. During the study period between 1996 and 1997, a total of
17,974 adults with diagnosed AF were identified. The overall
prevalence of AF was 0.95%, and AF was more common in men
than in women (1.1% and 0.8%, respectively) [16]. The prevalence
increased from 0.1% among adults younger than 55 years to 9.0%
in persons aged 80 years or older. Therefore, 45% of all affected
subjects were aged 75 years or older [16], again demonstrating
that the prevalence of AF gradually increased with aging. This
trend was similar to that in the former four surveys [11–14] and
in the survey from the United Kingdom [15]. According to these
results [16], there were an estimated 2.3 million adults with AF in
the United States, which was comparable with the results
reported by Feinberg et al. [17] Assuming that the prevalence of
AF remains consistent with that reported in the ATRIA study, the
number of people with AF is projected to increase to more than
5.6 million by the year 2050, with more than 50% of affected
individuals being aged 80 years or older [16].
Gender differences in the prevalence of AF, which is generally
more common in men than in women, are consistently reported.
The prevalence of AF in men was 1.5-fold higher than in women
in the Framingham study [13]. A racial difference was also
pointed out in the ATRIA study [16], in which the prevalence of
AF in whites was 2.2%, whereas in blacks among those aged 50
years or older it was 1.5%.
Time trends in the prevalence of AF have been clarified from
studies that performed periodic check-ups including ECG record-
ings over long periods. In the Framingham study [18], the
prevalence of AF in adults aged 65–84 years was 3.2% in men
and 2.8% in women during the period between 1968 and 1970,
and 9.1% in men and 4.7% in women between 1987 and 1989. The
increase in the prevalence of AF in men, 2.8-fold, was marked
during this approximately 20-year period, whereas it was only
1.7-fold in women. Similarly, in the Copenhagen City Heart Study
[19], AF in adults aged 50–89 years was 1.4% in men and 1.5% in
women during the period between 1976 and 1978 and was 3.3%
in men and 1.1% in women between 1991 and 1994. Thus, a
2.4-fold increase in the prevalence of AF was found in men, while
no increase was observed in women. The reasons for these gender
differences over time in the trends in the prevalence of AF remain
unclear.
Table 2
Age- and gender-specific prevalence of atrial fibrillation in Australia, Europe, and the United States.
Western Australia Rochester Framingham Cardiovascular Health Study UK database ATRIA study
Report year (references) 1989 [11] 1990 [12] 1991 [13] 1994 [14] 2001 [15] 2001 [16]
Number of subjects 1770 2122 5070 5201 140 10
4
189 10
4
Age (years) Men Women Overall Men Women Overall Overall Men Women Overall Men Women Men Women Overall
40–44 0 0 0 0.1 0.25 0.22
45–49 0.5 0.5 0.5 0.1 0.66 0.44
50–54 0.5 0.5 0.5 0.5 0.66 0.44
55–59 1.0 1.5 1.2 0.5 1.8 1.1 0.9 0.4 0.6
60–64 1.1 2.3 1.7 1.0 1.5 1.2 1.8 1.8 1.1 1.7 1.0 1.4
65–69 3.3 2.7 3.0 6.0 3.0 4.6 1.8 5.9 2.8 4.0 4.6 3.3 3.0 1.7 2.5
70–74 8.6 5.5 7.0 6.0 3.0 4.6 4.8 5.8 5.9 5.8 4.6 3.3 5.0 3.4 4.3
75–79 15.0 8.4 11.6 16.1 12.2 13.7 4.8 5.8 5.9 5.8 9.1 7.2 7.3 5.0 6.3
Z80 15.0 8.4 11.6 16.1 12.2 13.7 8.8 8.0 6.7 7.3 10.6
a
10.9
a
10.6 8.0 9.3
The data are expressed as %.
If the age range was 10 years in the original paper, the same values are described for the two 5-year increments in the table.
Cited from the Guidelines for Pharmacotherapy of Atrial Fibrillation (JCS 2008) [10].
a
Z85 years old.
Fig. 1. The estimated number of people with atrial fibrillation compared with the US general population. The bars indicate the number of people ( 10
3
) with atrial
fibrillation per 5-year age group (right axis). The dotted line indicates the US population ( 10
3
) per 5-year age group (left axis, 1991 census data) (cited from Feinberg
et al. [17]).
E. Kodani, H. Atarashi / Journal of Arrhythmia 28 (2012) 330–337332

3.2. Prevalence of AF in Asia
Jeong [20] has reported the prevalence of AF in Korea, where
the population has largely maintained a traditional Asian lifestyle.
Among 14,540 adults aged 40 years or older who received general
health screenings in the year 2000 [20], the overall prevalence of
AF was 0.7% in adults older than 40 years and was 2.1% in those
older than 65 years. The prevalence was 1.2% in men and 0.4% in
women in people older than 40 years and was 3.3% in men and
1.1% in women among those participants older than 65 years
(Table 3). A total of 56.6% of the individuals with AF were older
than 65 years, and the prevalence of AF was highest in people
older than 80 years. A gender difference was again found, with a
greater prevalence of AF in men than in women at all ages
(Table 3)[20]. Reports of surveys of AF rates in other Asian
countries have been scarce. Therefore, large surveys that include
Asian populations are often consulted for information about the
prevalence of AF in Asians. For example, of 25,051 patients
evaluated in general practices in West Birmingham, a total of
14,670 Indo-Asians were included, and the prevalence of AF in the
Indo-Asian individuals aged over 50 years was 0.6% [21].
In Japan, the prevalence of AF was investigated in a long-
itudinal cohort study of the Radiation Effects Research Founda-
tion, a cooperative Japan–US Research Organization. A total of
6990 subjects received at least seven out of nine biannual check-
up examinations, including ECG recordings, and were followed
during the period between 1968 and 1986 [22]. The prevalence of
AF was about 0.2% in the 40s–early 50s age groups, 0.6% in the
late 50s, and increased almost linearly up to 2.5% by the time
participants were in their 80s. There was a difference in the
prevalence of AF among the generations evaluated in the study,
and the prevalence of AF increased during the later decade of this
longitudinal cohort study, despite the fact that the participants
were the same ages [22].
After this early study, three other epidemiological studies were
reported from Japan in the 1990s through the 2000s (Table 3).
There were 5000–6000 subjects in the first two population-based
studies, in a rural northeast Japanese community in Akita [23],
and in the National Survey on Cardiovascular Diseases in 2000
[24]. Moreover, a population-based study conducted with
the support of the Japanese Circulation Society [25] included
630,138 participants aged 40 years or older and was one of the
largest-scale surveys in Japan. The data were obtained from
periodic health examinations of community residents, employees
of companies, and local governments in 2003 [25]. Similar to the
results from previous surveys [23,24], the prevalence of AF in
elderly participants, especially those over 60 years old, was higher
than that in younger adults, and it was 3.2% in those aged 80 years
or older. The prevalence of AF was consistently higher in men
than in women among all age groups (Fig. 2), with an overall rate
of 1.35% in men and 0.43% in women, indicating an almost 3-fold
difference between the genders. These trends are similar to those
reported in Western countries.
Based on the Japanese Registry of Residents in 2005, the
overall prevalence of AF in Japan was estimated to be 0.56%
[25], indicating that the rate was approximately two-thirds of
that in the United States, which was reported to be 0.89% [17].
The number of people in Japan with AF was estimated to be
716,000 [25]. Similar to the United States, the age-specific pre-
valence of AF was highest at the age of 80 years or more, but the
absolute number of people with AF peaked between 70–79 years,
since the population of people in their 70s was higher than that of
people in their 80s. Eighty-five percent of the individuals with AF
were older than 60 years, and 25% were older than 80 years.
Table 3
Age- and gender-specific prevalence of atrial fibrillation in Japan and Korea.
Akita Cardiovascular Survey Japanese Circulation Society Korea
Report year (references) 1991 [23] 2005 [24] 2006 [25] 2005 [20]
Number of subjects (year of survey) 6057 (1984–1987) 5198 (2000) 630,133 (2003) 14,540 (2000)
Age (years) Men Women Total Men Women Total Men Women Total Men Women Total
40–44 1.2 0 0.5 0 0.2 0.1 0.2 0.04 0.1 0.12 0.06 0.1
45–49 1.2 0 0.5 0 0.2 0.1 0.2 0.04 0.1 0.12 0.06 0.1
50–54 1.2 0.6 0.9 0.4 0.7 0.6 0.8 0.1 0.4 0.7 0.4 0.5
55–59 1.2 0.6 0.9 0.4 0.7 0.6 0.8 0.1 0.4 0.7 0.4 0.5
60–64 3.0 1.1 1.9 1.4 0.5 0.9 1.9 0.4 1.0 1.8 0.2 0.9
65–69 3.0 1.1 1.9 1.4 0.5 0.9 1.9 0.4 1.0 3.9 1.0 2.2
70–74 (4.7) (3.0) (3.8) 3.5
a
2.1
a
2.7
a
3.4 1.1 2.1 2.5 1.1 1.7
75–79 (4.7) (3.0) (3.8) 3.5
a
2.1
a
2.7
a
3.4 1.1 2.1 3.4 0.5 1.9
Z80 3.5
a
2.1
a
2.7
a
4.4 2.2 3.2 4.5 3.5 4.0
Overall 2.1 0.8 1.4 – – 0.9 1.4 0.4 0.6 1.2 0.4 0.7
The data are expressed as %. The numbers in ( ) were derived from a small number of subjects.
If the age range was 10 years in the original paper, the same values are described for the two 5-year increments in the table.
Cited from the Guidelines for Pharmacotherapy of Atrial Fibrillation (JCS 2008) [10] and Jeong [20].
a
Z70 years old.
0
1
2
3
4
5
40-49
Men
Women
Age, y
Prevalence, %
50-59 60-69 70-79 ≥80
Fig. 2. The age- and gender-specific prevalence of atrial fibrillation in Japan
(adapted from Inoue et al. [25]).
E. Kodani, H. Atarashi / Journal of Arrhythmia 28 (2012) 330–337 333

Assuming that the prevalence of AF remains unchanged, the
number of people with AF in Japan is projected to be 1.034
million by 2050, with an overall prevalence of 1.09% (Fig. 3)[25].
These estimates are comparable to those from the National
Survey on Cardiovascular Diseases reported by Ohsawa et al.
(Fig. 3)[24].
In another community-based study in Japan that included a total
of 41,436 adult residents aged 40 years or older in Kurashiki-city in
2006, the observed rate of AF was 0.5% in men and 0.2% in women
aged 40–59 years, 2.3% in men and 1.0% in women aged 60–79
years, and 3.5% in men and 2.5% in women over 80 years, and the
overall prevalence was 1.6% [26]. These results were similar to those
of the study performed by the Japanese Circulation Society [25].
In the report by Ohsawa et al. [24], no increase in the age-
adjusted prevalence of AF was observed in the Japanese popula-
tion during 1980–2000. This trend was different from those
reported in Western countries [18]. However, the prevalence of
AF would be expected to increase in the future if the prevalence of
predisposing factors for AF, such as prior myocardial infarction,
heart failure, valvular disease, obesity, hypertension, and dia-
betes, increases, as it has in Western countries [24]. The reason
for the current discrepancy of time trends in the prevalence of AF
between Japan and Western countries would then be explained
by a time lag in the trends of predisposing factors between Japan
and Western countries.
4. Incidence and projected number of AF cases
Several epidemiological studies have reported the incidence of
AF in Western counties. In the Framingham study [27], chronic
and transient AF was identified in 26 in men and 16 in women
aged 70–79 years per 1000 people during a follow-up period of
2 years; thus, the overall incidence of AF was 0.2% per year in
men, and the highest rate was in subjects in their 70s (Fig. 4).
In the Cardiovascular Health Study [28], among 4844 participants,
304 developed a first episode of AF during an average follow-up of
3.28 years, for an incidence of 19.2 per 1000 person-years. For
men 65–74 and 75–84 years old, the incidence rates were 17.6
and 42.7, respectively, and for women, there were 10.1 and 21.6
events per 1000 person-years, indicating that the incidence of AF
in adults increased with age. A community-based study with
4618 adult residents of Olmsted County, Minnesota [29] also
showed that the incidence of AF increased with age, and was
higher in older adults than in younger adults, similar to the
Framingham study [30] and the Cardiovascular Health Study
(Fig. 5)[28]. The age- and sex-adjusted incidence rates of AF per
1000 person-years were 3.04 in 1980 and 3.68 in 2000. Therefore,
the incidence of AF in the overall cohort increased significantly,
with a relative increase of 12.6% over 21 years [29]. If this
increasing rate of incidence continues, the number of people with
AF is projected to reach 15.9 million by 2050. Even if the age-
adjusted incidence of AF remains the same as that in 2000, the
number of people with AF would still be estimated to be 12.1
million (Fig. 6). The projected number of individuals who will
develop AF by 2050 in the study in Minnesota [29] was much
greater than the 5.6 million predicted in 2050 in the study
by Feinberg et al. [17]. In 2009, Naccarelli et al. [31] reported an
updated estimate of the prevalence of AF using a larger
database of 21.6 million people of all ages. The number of people
with AF in 2005 was estimated to be 3.03 million, and was
projected to grow to 4.78 million in 2035 and 7.56 million in
2050. These estimates were larger than those projected by Go
0
20
40
60
80
100
120
1980
Women
Men
Survey of Japanese
Circulation Society
Year
Number of persons with AF, x10,000
1990 2000 2010 2020 2030 2040 2050
Fig. 3. The estimated and projected numbers of people with atrial fibrillation in
Japan. The bars indicate the number of people ( 10
4
) with atrial fibrillation in
each year in the National Survey on Cardiovascular Diseases [24]. The solid line
indicates the number of people ( 10
4
) with atrial fibrillation in the survey
performed by the Japanese Circulation Society [25] (generated using the data from
Ohsawa et al. [24] and Inoue et al. [25]).
Fig. 4. The incidence of atrial fibrillation in the Framingham study. The values are
expressed as the 2-year incidence of atrial fibrillation per 1000 persons. The solid
lines indicate the incidence in men, and the dotted lines indicate the incidence in
women (cited from Kannel et al. [27]).
Fig. 5. The incidence of atrial fibrillation per 1000 person-years stratified by age in
the Framingham Study [30], the Cardiovascular Health Study (CHS) [28], and the
Olmsted County Study [29]. The values are plotted at the midpoints of the age
ranges (data were originally cited in Miyasaka et al. [29]).
E. Kodani, H. Atarashi / Journal of Arrhythmia 28 (2012) 330–337334

et al. [16] but smaller than those of Miyasaka et al. [29].
The possible reasons for the differences in the projected preva-
lence of AF among these studies include differences in sample
sizes, geographical areas, and assumptions regarding the
increases in the incidence of AF [31].
The incidence of AF in Japan was also reported from an early
cohort of the Hisayama Study [32] in the period between 1961
and 1984. Similar to the reports from Western countries, the
incidence of AF increased with age in both men and women
(Fig. 7)[32]. In a recent report of an observational cohort study
based on an annual health check-up program in Niigata and
including 28,449 participants aged 20 years or older (mean 59.2
years), the incidence of AF per 1000 person-years was 4.1 in men
and 1.3 in women [33]. In another community-based study with
30,010 participants aged 40 years or older (median 73 years)
based on an annual health survey in Kurashiki [34], the incidence
of AF per 1000 person-years seemed to be higher (13.0 in men
and 7.4 in women), but that in the lowest age tertile (r67 years)
was comparable (5.3 in men and 1.5 in women) with that in
Niigata [33].
5. Ethnicity and AF
Most of the epidemiological data about AF from the Western
countries have been derived from predominantly white popula-
tions. Therefore, the prevalence of AF among groups of different
ethnicities or races should be evaluated with caution, since the
world literature on the clinical epidemiology of AF in non-white
groups is limited. Ethnic differences in cardiovascular disease and
stroke have been reported by Balarajan [35], in which a higher
prevalence of ischemic heart disease and hypertension was noted
in Indo-Asian populations and Afro-Caribbean populations,
respectively. A small number of reports on the prevalence of AF
in the other populations can also be found, which show differ-
ences in the mean age and the most common etiological causes of
AF. For example, Maru [36] reported a survey of 136 Ethiopian
cardiac outpatients with AF in whom the mean age was 41 years,
and the common etiological causes of AF were rheumatic heart
disease (66%), hypertension (10%), cardiomyopathy (9%), and
ischemic heart disease (7%). In contrast, in a review of 291
predominantly Chinese patients with AF who were treated at a
regional hospital in Hong Kong [37], the mean age was 73 years,
and the common etiological factors were hypertension (29%),
vascular disease (25%), and rheumatic heart disease (18%) [37].In
another survey of acute medical admissions for AF at a city center
hospital in Birmingham, UK, [5] serving a multi-ethnic population
of 300,000 (64% white, 11% black/Afro-Caribbean, 25% Indo-
Asian), 87% of the patients with AF were white, 4% were black/
Afro-Caribbean, and 9% were Indo-Asian, indicating that there
was a lower prevalence of AF in Indo-Asians compared to
whites [5]. In that survey [5], the predominant etiological factor
associated with AF in black/Afro-Caribbeans was hypertension
(50%), whereas in Indo-Asians, it was ischemic heart disease
(45.5%). However, this trend has changed in Japanese patients
with AF, since the predominant etiological factor according to
recent Japanese studies [38,39] has been hypertension, and not
ischemic disease.
6. Epidemiology of AF and future therapeutic strategies
Knowledge of the prevalence and the incidence of AF from
epidemiological surveys in general populations is important, and
knowledge of the characteristics of patients who have already
been diagnosed with AF and are receiving treatment is also
necessary for general physicians in order to ensure that optimal
medical care can be provided for these patients. Data obtained at
the time of registration in the J-RHYTHM Registry [39] are
currently available to provide information about Japanese AF
patients.
The J-RHYTHM Registry [39] is a multicenter prospective
observational study that is being performed to investigate the
present status and optimal intensity of anticoagulation in Japa-
nese patients with AF. Registration was terminated in July 2009.
A total of 7937 patients with AF from 158 institutions,
including 5468 men (68.6710.0 years) and 2469 women (72.27
9.0 years), were registered. Of these, 34.2% were over the age of
75 years. The type of AF was paroxysmal in 37.1%, persistent in
Age, y
1,000 person-years
Incidence of atrial fibrillation
1,000 person-years
Men
Women
Overall
(age-adjusted)
20
p<0.05
p<0.1 Iinearity
p<0.05
15
10
5
0
20
15
10
5
0
40–49 50–59 60–69 70–79 80–
Fig. 7. The age-specific incidence of atrial fibrillation in Japan. The results are from the early cohort of the Hisayama Study, with 1610 subjects evaluated between 1961
and 1984. The bars indicate the incidence of atrial fibrillation per 10-year increment of age (cited from Fujishima [32]).
Fig. 6. The projected number of persons with atrial fibrillation (AF) in the
United States between 2000 and 2050. Assuming no further increase in the age-
adjusted incidence of AF (solid curve), and assuming a continued increase in the
incidence rate observed as evident in 1980—2000 (dotted curve) (cited from
Miyasaka et al. [29]).
E. Kodani, H. Atarashi / Journal of Arrhythmia 28 (2012) 330–337 335

14.4%, and permanent in 48.5%. Overall, 87.3% of patients were
taking warfarin (2.971.2 mg/day), including co-administration
with aspirin. The CHADS
2
score [40] was 0 in 15.7% of the
patients, 1 in 34.0%, and Z2 in 50.3%, respectively, indicating
that almost half (49.7%) of the patients were in a low-risk group
for stroke.
The associated cardiovascular diagnoses were hypertension in
59.1% of the patients, coronary artery disease in 10.1%, cardio-
myopathy in 8.3%, valvular heart disease in 13.7%, and artificial
cardiac valves in 3.1%. Thus, hypertension was the most common
underlying disease in patients with AF (Table 4)[39], which is
consistent with the results of the J-RHYTHM study (42.8%) [38]
and various other previous investigations [7,16,41–44]. In addi-
tion, hypertension was the most common factor as a component
of the CHADS
2
score. Since blood pressure-lowering therapy
per se can contribute to inhibiting the new-onset or recurrence
of AF and prevent strokes, hypertension is thought to be an
extremely important therapeutic target for the management of
patients with AF.
Assuming that the incidence of cerebral infarction has the
same person-years value for each CHADS
2
score, as reported by
Gage et al. [40], i.e., 1.9% with a score of 0 and 2.8% with a score of
1, the number of patients suffering from a cerebral infarction
among the patients registered in the J-RHYTHM Registry is
projected to be 24 with a score of 0 and 76 with a score of 1,
despite the fact that these patients are evaluated to be in a low-
risk group. The scale of these numbers cannot be ignored, because
the total number of patients with a CHADS
2
score of 0 or 1 is very
large in Japan. Since a cardiogenic stroke is likely to be severe, and
its severity is not always in proportion to the CHADS
2
score,
interventions to prevent stroke should be considered even in the
patients in a low-risk group, i.e., those with a CHADS
2
score of 0 or
1. Anticoagulation therapy for these low-risk patients can be
performed referring to a new score for further risk stratification,
such as the CHA
2
DS
2
-VASc score [45].
7. Concluding remarks
The prevalence of AF is 2–3 times higher in men than in
women. The overall prevalence of AF is less than 1%, but the rate
in persons aged 80 years or older is approximately 7–14% in
Western countries and 2–3% in Japan. By 2050, the number of
people with AF is predicted to be 5–16 million in the United
States and more than 1 million in Japan. Further increases in the
prevalence and the incidence of AF are predicted in the future
with the increasing age of the population. Therefore, AF should be
considered a common disease, and it is likely that all physicians
will be confronted with patients presenting with AF at some point
in their daily clinical practice.
Conflict of interest
None.
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