The major risk factors for atrial fibrillation
in patients with hyperthyroidism are older age and male sex
(November 2004)
The background of the study. Atrial fibrillation
is a frequent manifestation of hyperthyroidism, but its reported
frequency has varied widely, and predisposing factors are not well
understood. This study determined the factors associated with atrial
fibrillation in a large group of patients with hyperthyroidism.
How the study was done. All patients with a hospital
discharge diagnosis of hyperthyroidism from 1977 through 1999, and
all patients with an outpatient diagnosis of hyperthyroidism from
1995 through 1999 were identified in the Danish National Registry
of Patients. All patients with a diagnosis of atrial fibrillation
were similarly identified. Data on hypertension, coronary heart
disease, valvular heart disease, heart failure, and diabetes mellitus
before or at the time of diagnosis of hyperthyroidism also were
obtained.
The results of the study. There were 40,628 patients
with hyperthyroidism (34,513 women [85 percent], 6115 men [15 percent]);
48 percent were aged 20 to 59 years, and 52 percent were 60 to 89.
Five percent had hypertension, 7 percent coronary heart disease,
1 percent valvular heart disease, 4 percent heart failure, and 4
percent diabetes.
Among the patients with hyperthyroidism, 3362 (8 percent) had atrial
fibrillation; they included 2621 of the women [8 percent], and 741
of the men [12 percent]). The frequency of atrial fibrillation increased
progressively with age, ranging from 0.3 percent among the patients
aged 20 to 29 years to 19 percent of those 80 to 89. Other risk
factors for atrial fibrillation, in addition to male sex and increasing
age, were heart failure and coronary and valvular heart disese.
The conclusions of the study. Atrial fibrillation
is more common in men than in women with hyperthyroidism, and its
frequency increases markedly with age.
The original article. Frost L, Vestergaard P,
Mosekilde L. Hyperthyroidism and risk of atrial fibrillation or
flutter: a population-based study. Arch Intern Med 2004;164:1675-8.
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