Day-of-the-week variations in myocardial infarction onset over a 27-year period: the importance of age and other risk factors.

Introduction: The aim of this study was to analyze the day-of-the-week variations of acute myocardial infarction (AMI) over a 27-year period. The effects of sex, age, history of AMI, hypertension, fatality, and temporal changes over the 27-year period were also investigated.

Methods: The Charleroi register of ischemic cardiopathies is the oldest register of infarctions in the French-speaking community of Belgium and is one of the very rare registers that can track trends over 27 years. The analyses presented in our study relate only to patients in the 25- to 69-year age range over time from 1983 to 2009. The χ2 test for goodness of fit was used to test the difference among the frequencies of AMI events over 7 days during the week.

Results: Data from 9732 cases of AMI were analyzed. Overall, there was a significant day-of-the-week variation (P<.001), with an excess of AMI observed on Mondays (n=1495) and a minimum on Saturdays (n=1259), corresponding to a relative increase in AMI of 18.2% over the 2 days. The Monday peak is more pronounced for the 35- to 44-year (P=.045) age bracket than for the 45- to 54-year (P=.27) and the 55- to 64-year (P=.032) brackets. The cases with (n=2713) and without (n=4931) arterial hypertension exhibited the same day-of-the-week variation. In contrast, the cases with antecedent AMI (n=1888) exhibited a less pronounced excess of MI incidence on Mondays compared with the cases without antecedent (n=5970).

Conclusions: The present study demonstrates that there is a marked incidence peak in AMI on Mondays. This peak is similar for men and women but varies according to age. The Monday peak is not observed in subjects previously admitted for AMI or in fatal cases. The organization of the emergency medical services could take into account the day-of-the-week pattern of AMI to adapt emergency medical service capacity to needs.