Background: Seasonal peaks in acute myocardial infarction (AMI) incidence have been widely reported. Weather has been postulated to be one of the elements at the basis of this association. The aim of our study was to determine the influence of seasonal variations and weather on AMI hospital admissions.
Methods: We correlated the daily number of AMI cases admitted to a western Sicily hospital over twelve years and weather conditions on a day-to-day basis. Information on temperature, humidity, wind force and direction, precipitation, sunny hours and atmospheric pressure was obtained from the local Birgi Air Force base. A total of 3918 consecutive patients were admitted with AMI over the period 1987-1998 (2822 men, 1096 women; M/F: 2,58).
Results and conclusions: A seasonal variation was found with a significant winter peak. The results of multivariate Poisson analysis show in both sexes a significant association as regards the incidence relative ratio between the daily number of AMI hospital admission and minimal daily temperature and maximal daily humidity. The incidence relative ratios (95% confidence intervals) were, in males, 0.95 (0.92-0.98) (p<0.001) as regards minimal temperature and 0.97 (0.94-0.99) (p=0.017) as regards maximal humidity. The corresponding values in females were respectively 0.91 (0.86-0.95) (p<0.001) and 0.94 (0.90-0.98) (p=0.009). Environmental temperature, and also humidity, may play an important role in the pathogenesis of AMI. These data may help in understanding the mechanisms whereby AMI events are triggered and in organizing better the assistance to ischemic patients throughout the year.