Afternoon nap, meal ingestion and circadian variation of acute myocardial infarction

A two-peaked circadian variation in acute myocardial infarction has been demonstrated, with a morning peak attributed to physiological changes produced by nocturnal sleep. To investigate the causes of the secondary peak, we compared meal habits and circadian variation in patients with acute myocardial infarction who were accustomed to afternoon naps (group A) to those who were not (group B). One hundred and fifty two patients formed group A and 65 group B. The main meal was lunch in group A (77%) and dinner in group B (74%). Both groups displayed a significant circadian variation, (group A: x2 = 51.3, group B: x2 = 60.4, both p < 0.0001), but the secondary peak occurred earlier (2pm–4pm) in group A, than in group B (6pm–8pm). We conclude that ingestion of the main daily meal, followed by a period of physical inactivity, with or without sleep, is a trigger for acute myocardial infarction.