RESUME Cette étude a permis de déterminer la prévalence de la fibrillation auriculaire dans un centre de soins de santé primaires de la province de Fars (République islamique d’Iran). Tous les patients ambulatoires âgés de 50 ans ou plus qui ont consulté au centre entre avril et octobre 2001 ont subi un examen à la recherche d’une fibrillation en réalisant un ECG standard à 12 dérivations. L’âge moyen des participants était de 64,0 ± 8,9 ans. Sur les 463 participants âgés de 50-79 ans, 13 (2,8 %) avaient une fibrillation auriculaire (âge médian 74 ans) ; il y avait un nombre significativement plus important de femmes (10/230) que d’hommes (3/233). Contrairement aux études précédentes réalisées dans les pays industrialisés, la prévalence triplait à chaque décennie de vie et augmentait de manière significative, de 0,6 % dans le groupe d’âge des 50-59 ans à 6,4 % dans celui des 70-79 ans. Compte tenu de l’accroissement de la longévité dans certains pays en développement, la fibrillation auriculaire et donc les accidents vasculaires cérébraux peuvent devenir des problèmes de santé majeurs.

First described almost 100 years ago, atrial fibrillation is now the most common clinically important sustained cardiac arrhythmia [1,2]. Atrial fibrillation is associated with a substantial morbidity [2,3] and is a major health care burden for many countries. The arrhythmia is the complete absence of coordinated atrial systole, charac- terized on the electrocardiogram (ECG) by the absence of ‘P’ waves before each QRS complex and the presence of rapid, irregular ‘F’ waves that vary in size, shape and timing. Atrial fibrillation is a potent predisposing factor for ischaemic stroke, and is associated with a 5-fold increase in risk [4,5]. Those with rheumatic heart disease and atrial fibrillation have an even higher (17-fold) increased risk of stroke [1]. It may also be an independent risk factor for death, with a relative risk of around 1.5 for men and 1.9 for women after adjustment for known risk factors [6].

The prevalence of atrial fibrillation reported in various studies, mostly conducted in industrialized countries, doubles with each decade of life and ranges from 0.05% among persons aged 25–35 years to 13.7% in those aged 80 years or older [7,8]. Nevertheless, little information is available about the prevalence of the disorder in developing countries. This study was conducted to determine the prevalence of atrial fibrillation in people aged 50 years and older attending a primary health care centre in Fars province in the south of the Islamic Republic of Iran.

The diagnosis of atrial fibrillation (complete absence of coordinated atrial systole, characterized by the absence of ‘P’ waves before each QRS complex and the presence of rapid, irregular ‘F’ waves that vary in size, shape and timing) was made after recording a single standard resting 12-lead surface ECG (Fukuda Cardisuny 501B-III, Japan) with a 1-minute rhythm strip.

The epidemiology of atrial fibrillation in this health centre in the south of the Islamic Republic of Iran is different from that of industrialized countries. In contrast to previous studies that found higher rates of atrial fibrillation among men [1,2,5], we found the prevalence was higher in women (10/13) than men (3/13) (P < 0.05).

Nowadays, atrial fibrillation is more often treated as a sign of an underlying disease than a disease entity in its own right. The most important underlying cardiac disorders consist of heart failure, coronary artery disease, hypertensive cardiovascular disease and valvular heart diseases [9,10]. Mitral stenosis is important in the etiology of atrial fibrillation [11]. Mitral stenosis mostly results from rheumatic fever, a disease that is currently not frequent in industrialized countries, owing to better treatment with antibiotics and increased health standards [10]. In developing countries, however, where rheumatic fever is still a health problem, mitral stenosis is much more frequent. Since mirtal stenosis affects females twice as often as males [10], in developing countries the sex ratio of patients with atrial fibrillation would be reversed, and women might be expected to develop atrial fibrillation much more often than men.

Like previous studies, mostly conducted in industrialized countries, we observed that the prevalence of atrial fibrillation increases with age [5]. The median age of 74 years in our patients is in keeping with that reported in other studies [4,5]. Go et al. [4] reported a prevalence of 1.8% in patients aged 60–69 years and 4.9% in 70–79 years, compared with 1.4% and 6.5% respectively in our study. Comparing our results with these, we found no statistically significant difference between the reported prevalences over the age range 60 to 80 years. However, unlike previous reports that show a 2-fold increase in the prevalence of atrial fibrillation with each decade of life [2,5], in our population this trend was much steeper and instead increased 3-fold with each decade over the age range studied. This accelerated trend may be due to ethnic differences and/or to the underlying causes in our population. In industrialized countries, ischaemic heart disease is the most important cause [9], whereas in developing countries, though it was not studied here, valvular heart disease, particularly mitral stenosis, seems to be the cause of atrial fibrillation in the majority of cases.

This study suffers from some limitations. Estimates of the prevalence of atrial fibrillation vary according to the characteristics of the population studied and the way atrial fibrillation is ascertained. In the current study, the diagnosis of atrial fibrillation was made on a single ECG. Hence, we might miss some people with non- sustained atrial fibrillation. Moreover, given the small sample size used in this study as compared with those conducted in industrialized countries, the statistical power of the current research is low. Likewise, the small number of cases with atrial fibrillation diagnosed in this study, particularly when they were categorized into age groups, means that we were only able to derive a rough estimate of the prevalence rates. Nevertheless, the results obtained from this work were statistically significant and the steep trend of increasing prevalence of atrial fibrillation at older ages is noteworthy. With improved health standards and increasing longevity in some developing countries [12,13], atrial fibrillation and consequently stroke may become increasingly important health problems.

13. Shrestha LB. Population aging in developing countries. Health affairs (Mill-wood), 2000, 19:204–12.