Circulation. 1999;100:e153
(Circulation. 1999;100:e153.)
© 1999 American Heart Association, Inc.
Circulation Electronic Pages |
Atrial Fibrillation and Ethnicity
Christopher R. Gibbs;
Gregory Y. H. Lip
University Department of Medicine,
City Hospital,
Birmingham, UK
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Introduction
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To the Editor:
Benjamin et al1 address the risk of atrial
fibrillation (AF) in the Framingham Study with a longitudinal
population design, which overcomes the common problem of selection
bias. However, the study sample was predominantly white, and the one
epidemiological question that remains unanswered is the relationship
between race and the incidence of AF.
Although there are recognized ethnic differences in
cardiovascular disease and stroke, the world literature
on the clinical epidemiology of AF in nonwhite
groups is scarce. We are only aware of small surveys on the prevalence
of AF in nonwhites from Africa,2 Japan,3 and
Hong Kong,4 in addition to our work in a multiethnic
population in Birmingham, England.5
For example, Maru2 reported 136 Ethiopian cardiac
outpatients with AF, in whom the mean age was 41 years, and the
commonest causes were rheumatic heart disease (66%), hypertension
(10%), cardiomyopathy (9%), and ischemic
heart disease (7%). A Japanese report3 of secular trends
in the prevalence and incidence of AF among a rural population found an
association of AF with hypertension, but >80% did not have heart
disease or thyroid disease. In a review of 291 predominantly Chinese
patients, the mean age was 73 years, and the commonest etiological
factors were hypertension (29%), vascular disease (25%), and
rheumatic heart disease (18%).4
In our survey of acute medical admissions with AF, 87% were
white, 4% were black/Afro-Caribbean, and 9% were
Indo-Asian.5 The predominant etiological factor associated
with AF in our Afro-Caribbean patients was hypertension, whereas in
Indo-Asians, it was ischemic heart disease.5
Indo-Asian patients with AF in our study were also younger (mean age 62
years) than Afro-Caribbeans and whites (mean ages of 73 and 75 years,
respectively). Our survey of 6 general practices with a combined
population of 25 051 (65% Indo-Asians) only identified 12 Indo-Asian
patients (mean age 67 years) with known AF, suggesting a prevalence of
AF of 0.6% in Indo-Asians aged >50 years. The commonest associated
medical conditions were ischemic heart disease, heart failure,
hypertension, and valve disease. The lower prevalence of AF among
Indo-Asian patients in general practice compared with our hospital
survey may be a reflection of a higher relative proportion of
Indo-Asians with AF who required hospital admission, perhaps due to
concurrent ischemic heart disease (or complications) that could
make such patients more unwell. Our previous general practice survey
had suggested that only a third of patients with AF had ever
presented to hospital, suggesting that hospital-centered
surveys may misrepresent the true picture of the clinical
epidemiology of AF. In addition, scant
information is available on ethnic variations in the prescribing of, or
compliance with, thromboprophylaxis for the prevention of stroke and
thromboembolism.
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References
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Benjamin EJ, Wolf PA, D’Agostino RB, Silbershatz
H, Kannel WB, Levy D. Impact of atrial fibrillation on the risk of
death: the Framingham Heart Study. Circulation. 1998;98:946–952.[Abstract/Free Full Text]
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Maru M. Atrial fibrillation and embolic
complications. East Afr Med J. 1997;74:3–5.[Medline]
[Order article via Infotrieve]
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Kitamuru A, Shimamoto T, Doi M, Iso H, Miyagaki
T, Sankai T, Komachi Y, Iida M, Tanigaki M, Naito Y. Secular trends in
prevalence and incidence of atrial fibrillation and associated factors
in a Japanese rural population. Nippon Koshu Eisei Zasshi. 1991;38:95–105.[Medline]
[Order article via Infotrieve]
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Lok NS, Lau CP. Presentation and
management of patients admitted with atrial fibrillation: a review of
291 cases in a regional hospital. Int J Cardiol. 1995;48:271–278.[Medline]
[Order article via Infotrieve]
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Zarifis J, Beevers DG, Lip GYH. Acute admissions
with atrial fibrillation in a British multiracial hospital population.
Br J Clin Pract. 1997;51:91–96.[Medline]
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Response
Emelia J. Benjamin, MD, ScM,;
Philip A. Wolf, MD,;
Ralph B. D’Agostino, PhD,;
Halit Silbershatz, PhD,;
William B. Kannel, MD,;
Daniel Levy, MD
The Framingham Heart Study,
Framingham, Mass
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Introduction
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We thank Drs Gibbs and Lip for their interest in our work. As
acknowledged
in the article, the generalizability of our finding of an
association
of atrial fibrillation and increased risk of death remains
to
be established in other racial and ethnic minorities.
1
Aside
from the work cited by Drs Gibbs and Lip, there are few published
studies
of atrial fibrillation in nonwhite populations. The existing
literature
hints that there are racial and ethnic differences in the
epidemiology
of atrial fibrillation. However,
ethnic and international comparisons
of the prevalence of atrial
fibrillation are hampered by differences
in study design. For instance,
a study of 984 Himalayan village
residents in India found a prevalence
of atrial fibrillation
of only 0.1% (n=1).
2 However, the
participants were healthy,
received only a single ECG, and only 6%
were >65 years of
age. Racial differences in the prevalence of atrial
fibrillation
are also suggested by the Cardiovascular
Health Study, a 4-community
study of the elderly in the United States.
Blacks constituted
only 5% of the study sample, but the investigators
noted that
there was a trend for blacks to have a lower incidence of
atrial
fibrillation than whites (relative risk 0.47, 95% CI
0.22–1.01).
3 However, it is unclear whether or not these
racial differences
would have persisted if the analysis had
been restricted to
atrial fibrillation detected on routinely
ascertained study
ECGs.
There is a similar paucity of data regarding ethnic differences
in the prognosis and treatment of atrial fibrillation. The Atrial
Fibrillation Investigators noted that only 5% of patients enrolled in
randomized controlled trials of warfarin were nonwhite; the
investigators did not comment on racial differences in stroke
rate.4 In contrast, in a prospective study of
ischemic stroke patients in northern Manhattan (35% black,
46% Hispanic, and 19% white), a history of atrial fibrillation was
less prevalent in both blacks (11%) and Hispanics (11%) than among
whites (29%; P<0.01 for black versus white and for
Hispanic versus whites). However, the latter analysis was
unadjusted.5 In summary, we concur with Drs Gibbs and Lip
that there is a regrettable lack of knowledge about the
epidemiology, prognosis, and treatment of
atrial fibrillation in ethnic minorities and for much of the developing
world.6 We hope these deficits will be rectified soon.
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References
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Benjamin EJ, Wolf PA, D’Agostino RB, Silbershatz H,
Kannel WB, Levy D. Impact of atrial fibrillation on the risk of death:
the Framingham Heart Study. Circulation. 1998;98:946–952.
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Kaushal SS, DasGupta DJ, Prashar BS, Bhardwaj AK.
Electrocardiographic manifestations of healthy residents of a tribal
Himalayan village. J Assoc Phys India. 1995;43:15–16.
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Psaty BM, Manolio TA, Kuller LH, Kronmal RA,
Cushman M, Fried LP, White R, Furberg CD, Rautaharju PM. Incidence of
and risk factors for atrial fibrillation in older adults.
Circulation. 1997;96:2455–2461.[Abstract/Free Full Text]
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Atrial Fibrillation Investigators. Risk factors
for stroke and efficacy of antithrombotic therapy in atrial
fibrillation: analysis of pooled data from five randomized
controlled trials. Arch Intern Med. 1994;154:1449–1457.[Abstract]
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Sacco RL, Kargman DE, Zamanillo MC. Race-ethnic
differences in stroke risk factors among hospitalized patients with
cerebral infarction: the Northern Manhattan Stroke Study.
Neurology. 1995;45:659–663.[Abstract/Free Full Text]
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Ryder KM, Benjamin EJ. Epidemiology and significance of atrial
fibrillation. Am J Cardiol.. 1999;84:131R–138R.[Medline]
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Introduction
References