TROMSOE, NORWAY. A team of researchers from the University of Tromsoe reports the results of an 11-year study aimed at determining major risk factors for the development of atrial fibrillation (AF). The 22,815 participants, for whom the necessary data was available, were part of the Tromsoe Study started in 1974 to determine risk factors for, and incidence of, cardiovascular disease in the municipality of Tromsoe. During the period 1994 to 1995 the all the participants (aged 25 to 96 years) underwent a thorough medical examination and answered a comprehensive questionnaire. One of the questions asked was, have you noticed sudden changes in your heart rate or heart rhythm in the past year? During the mean follow-up of 11.1 years, 361 women (3.0%) and 461 men (4.2%) were diagnosed with AF documented on an electrocardiogram. This corresponds to an incidence rate of 0.27%.year in women and 0.39%/year in men. At the end of the follow-up, further examinations were made to determine if the participants had developed, or still had, coronary artery disease, congestive heart failure, valvular heart disease, and enlarged atria. Participants with AF who were free from heart disease, hypertension and diabetes, and who were under the age of 65 years at the time of AF diagnosis were considered to have lone atrial fibrillation (LAF). Only 49 participants met this rather strict definition, indicating that 6% of the entire AF population of 361 had LAF. Considering the entire study population, only 0.21% developed LAF during the 11-year follow-up.
The main risk factors for developing AF are listed below (percent relative risk increase associated with the indicated risk factor when compared to the group without AF):