Circadian Variation in the Onset of Myocardial

There are conflicting reports regarding circadian varia-tion in the onset of acute myocardial infarction (MI) among patients with diabetes. We therefore, studied the circadian pattern of the incidence of acute MI in pa-tients (n 3,882) who were enrolled in the Onset Study stratified by the presence, type, and duration of diabe-tes. The Onset Study was conducted at 64 U.S. medical centers between August 1989 and September 1996. We used harmonic regression model to evaluate the circa-dian variation of MI symptom onset in patients with and without diabetes. Subgroup analysis was performed ac-cording to the presence, type, and duration of diabetes by the 2 test (dividing the day into four 6-h intervals). Patients without diabetes exhibited a prominent morn-ing peak in the incidence of acute MI symptom onse