Original Contribution Day-of-the-week variations in myocardial infarction onset over a 27-year period: the importance of age and other risk factors ☆ Philippe Collart ⁎, Yves Coppieters, MD, PhD, Isabelle Godin, PhD, Alain Levêque, MD, PhD Research Centre in Epidemiology, Biostatistics and Clinical Trials, School of Public Health, Université Libre de Bruxelles (ULB), Route de Lennik 808, CP 596, 1070 Brussels, Belgium abstract article info Article history: Received 25 October 2013 Received in revised form 2 February 2014 Accepted 10 February 2014 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 χ 2 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 b .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. © 2014 Elsevier Inc. All rights reserved. 1. Introduction Cardiovascular diseases are the primary causes of mortality in Belgium [1]. To monitor these important and problematic health aspects, in 1983, Belgium set up a register of acute coronary events in the region of Charleroi. This register is part of the international project “Monitoring Trends and Determinants in Cardiovascular Disease” (MONICA) coordinated by the World Health Organization. The standardized register has been operating for 27 years. The register collects all suspected cases of acute myocardial infarction (AMI) through a system involving all hospitals. Additionally, the register enables the analysis of death certificates. The aim of the register is (1) to contribute to the promotion of the quality in medical care provided by generalist and specialist health professionals, (2) to improve health system management, and (3) to plan prevention programs. The incidences of AMI vary according to the day, the week, the season, and the year [2-4]. The increased incidence in the morning is attributable to increased blood pressure and heart rate [4]. An increase in AMI is also observed in winter compared with summer [5]. The increase in the incidence of AMI in the cold months is a consequence of a variety of causes, such as increased C-reactive protein, vasoconstriction, and increased blood pressure [5]. The incidence of AMI and the mortality attributed to this disease have declined markedly in Northern and Western Europe over the past 35 to 40 years [2]. Numerous studies reveal a day-of-the-week variation in the incidence of AMI, with a peak on Mondays [2,6-8]. However, only a few studies have investigated age and risk factor effects. None of the studies have reported long-term trends. Most of the articles refer to stress from commencing work week activity and a relative increase in inactivity as triggers of AMI [2]. Many studies have also reported that heavy alcohol consumption or binge drinking might trigger AMI [9-11]. The aim of this study was to analyze the day-of-the-week variations of 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 investigated. The day-of-the-week variations in the fatality rate associated with AMI were also investigated. American Journal of Emergency Medicine 32 (2014) 558–562 ☆ Conflict of interests: The authors declare that they have no conflicts of interest. ⁎ Corresponding author. Tel.: + 32 2 555 40 93; fax: + 32 2 555 40 49. E-mail address: philippe.collart@ulb.ac.be (P. Collart). http://dx.doi.org/10.1016/j.ajem.2014.02.012 0735-6757/© 2014 Elsevier Inc. All rights reserved. Contents lists available at ScienceDirect American Journal of Emergency Medicine journal homepage: www.elsevier.com/locate/ajem