Seasonal Variation in Onset of Myocardial Infarction—A 7‐year single‐center study in Italy

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Abstract
Like many other serious acute cardiovascular and cerebrovascular events, acute myocardial infarction (AMI) shows seasonal variation, being most frequent in the winter. We sought to investigate whether age, gender, and hypertension influence this pattern. We studied 4014 (2259 male and 1755 female) consecutive patients with AMI presenting to St. Anna Hospital of Ferrara, Italy between January 1998 and December 2004. Some 1131 (28.2%) of the AMI occurred in persons vs. 56.6% in the ≥65 yr group (χ2=13.99; pn=614 or 20.1%) than the 964 hypertensive cases (n=77 or 8%; χ2=74.94, pn=1076 or 26.8% of all the events) and least in the summer (n=924 or 23.0% of all the events; χ2=12.36, p=0.007). The greatest number of AMIs occurred in December (n=379 or 9.44%), and the lowest number in September (n=293 or 7.3%; χ2=11.1, p=0.001). Inferential chronobiological (Cosinor) analysis identified a significant annual pattern in AMI in those ≥65 yrs of age, with a peak between December and February—January for the total sample (pp=0.014), February for fatal infarctions (p=0.017), and December for non‐fatal infarctions (p=0.006). No such temporal variations were detected in any of these categories in those n=552: January, p=0.014), non‐fatal infarctions in hypertensive patients (n=887: January, p=0.018), and elderly normotensives (n=1556: November, p=0.007).