Incidence of acute-onset atrial fibrillation correlates with air temperature. Results of a nine-year survey.

Some diseases, such as renal colic, stroke, and myocardial infarction, correlate with seasonality and microclimatic variations. Although evidence is limited and controversial, a correlation between acute-onset atrial fibrillation (AAF) and seasonality has been previously reported. In order to elucidate the possible correlations between weather and incidence of AAF in a country with a temperate climate, the influence of day-by-day climate changes was analyzed based on the number of visits for AAF (defined as onset of symptoms within 48h) in a large urban Emergency Department (ED) of northern Italy. All the episodes of AAF were retrieved from the hospital's electronic database during a period of 3287days (January 2002 to December 2010). Only the cases whose onset occurred within 48h from the ED visit were selected. The total number of ED visits was 725,812 throughout the observational period. Among these, 3633 AAF cases were observed, 52% of which were males. A slight but significant negative linear correlation was found between the number of AAFs and the daily temperature (R=-0.60; p=0.001). No correlation was found between the number of AAFs and the daily humidity (R=-0.07; p=0.2).