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where the rurality of the study location was not explicitly stated
in the paper, we contacted the corresponding authors to conﬁrm
whether their study was conducted in a rural, urban, or mixed
setting. Nineteen of the 26 authors (73%) whom we contacted
responded to our inquiry. Studies that were conducted in mixed
populations but separately reported AF prevalence in rural and
urban areas met our inclusion criteria.
The following information was extracted from the manuscript and recorded in a table: authors' name, year of publication, country of origin, study design, number of participants,
age range, median age, gender distribution, screening strategy,
and overall AF prevalence. Studies not published in English
were translated using Google Translator. If data were missing in
the paper of interest, the study authors were contacted for this
missing information. In one instance where the AF prevalence
was not reported in the original paper, we used data from a
subsequent systematic review.
The overall prevalence rate was estimated using the proportion of identiﬁed AF across all studies. A binomial conﬁdence
interval was calculated for the overall prevalence. Subgroup
analysis considered screening duration (i.e., screening period
of <1 year and >1 year). Studies that did not specify screening
duration were excluded from the subgroup analysis.
RESULTS
After removal of duplicate records, a total of 1424 articles
were screened against our inclusion and exclusion criteria. We
reviewed the full text of 75 articles and identiﬁed 18 studies
to include in our ﬁnal analysis (Figure 1). These 18 rural AF

Figure 1. Study selection and stratification.
July 2017

screening and prevalence studies published between 1965 and
2016 were conducted in 11 diﬀerent countries: Australia (n =
2), China (n = 3), Ghana (n = 1), Greece (n = 2), Ireland (n =
1), Japan (n = 4), Korea (n = 1), Spain (n = 1), Tanzania (n =
1), Thailand (n = 1), and USA (n = 1). Our search did not yield
any studies from South American countries.
There were 7 prospective cohort studies and 11 cross-sectional studies (Table 1) (14-31). Participants were recruited
either from population-based screening programs, annual health
checks, or general practitioner clinics. Seventeen out of the 18
studies (94.4%) utilized a 12-lead electrocardiogram (ECG) to
detect AF, while one study used a single-lead handheld ECG
device (29). Two studies also measured the heart or pulse rate
in conjunction with the 12-lead ECG (27, 31).
The total number of participants was 123,923, while the
sample size for each study ranged from 720 to 41,436 individuals. There were diﬀerent cut-oﬀs for participants' age: ≥16, 18, 20,
21, 35, 40, 50, 60, 65, and 70 years old. Men comprised 39%
(n = 48,336) of the total, with a frequency range of 33.6% to
52.0%. Two studies from China (26, 29) compared AF burden
for both urban and rural residents. One study from Australia
(23) was conducted in four regional towns in Victoria. However, data from one town was excluded since it is considered a
metropolitan area despite being regional. The overall prevalence
of AF from all studies was 2.05% (95% conﬁdence interval,
1.97%-2.13%) and ranged from 0.3% to 10.87%. The lowest
AF prevalence was observed in a community setting in Ghana,
while the highest prevalence was from opportunistic screening
in general practice clinics in Ireland. Follow-up was done in the
Australian Busselton Health Study from 1966 to
1981 (16) and the Shibata Study of Japan (15). The
Kurashiki Annual Medical Survey Study in 2006
(19) had a subsequent publication that found the
overall incidence of newly documented AF to be
9.3 per 1000 patient-years between 2006 and 2007
(32). Pooled prevalence for studies with a screening
period of ≤1 year was higher (2.25%) than that in
studies with >1 year of screening duration (1.61%).
The factors that were more commonly considered in the analyses of published studies were
gender, age, alcohol and smoking history, physical
activity, history of hypertension, diabetes, hyperlipidemia, myocardial infarction, cardiac disease,
liver disease, chronic kidney disease, body mass
index, blood pressure, and ECG and echocardiogram measurements (e.g., left ventricular hypertrophy, left ventricular ejection fraction, left atrial
dimensions). Blood tests analyzed included hematocrit, liver assays (alanine transaminase, aspartate transaminase), lipid proﬁle (total cholesterol,
high-density lipoprotein, low-density lipoprotein,
triglycerides), renal function tests (creatinine, glomerular ﬁltration rate), glucose measurements (fasting blood sugar, glycosylated hemoglobin A1C),
and cardiac biomarkers (brain natriuretic peptide,
high-sensitivity C-reactive protein). Signiﬁcant risk

Review of screening studies for atrial fibrillation in rural populations of 11 countries

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