Circadian and Seasonal Distribution of Cardioembolic Strokes Due to Atrial Fibrillation

time distribution of the onset of symptoms over 24 hours and one year, respectively. The ¯ 2 test (“goodness of fit” model) was then used to compare the incidence of CES per two-hour interval over 24 hours, per month and per season over the course of the year, with the expected values in each case. Results: There was a statistically significant difference (p<0.001) between the actual findings and a uniform 24-hour distribution. The daily distribution was unusual, with 2 peaks between 08:00-10:00 and 16:00-18:00. There was a similar difference (p<0.001) in the comparison over the year, with an increased incidence being apparent during the winter months. The differences between the seasons were also significant, with the largest number of CES during the winter and the smallest during the summer. Conclusions: The well-established increase in stroke in the morning, just a few hours after awakening, is probably related to corresponding changes in various biological parameters. The appearance of a second peak late in the afternoon may similarly be related to awakening from siesta. Further population studies are needed to confirm the increased incidence of CES during the winter months.