Seasonal and weekly patterns of hospital admissions for nonfatal and fatal myocardial infarction

doi:10.1016/j.ajem.2008.08.009

The American Journal of Emergency Medicine

Volume 27, Issue 9, November 2009, Pages 1097-1103

https://doi.org/10.1016/j.ajem.2008.08.009 Get rights and content

Abstract

Objective

This retrospective study, based on the database of hospital admissions of the region Emilia-Romagna [RER], Italy, was aimed to confirm the existence of a seasonal or weekly pattern of hospital admission of acute myocardial infarction (AMI) and to verify possible differences between nonfatal or fatal cases.

Methods

The study included all cases of patients with AMI hospitalized between 1998 and 2006. Day of admission was categorized, respectively, into four 3-month intervals, into twelve 1-month intervals, and into seven 1-day intervals for statistical analysis, performed by χ² test goodness of fit and partial Fourier series on total cases, males, females, and nonfatal and fatal cases.

Results

The database included 64 191 cases of AMI (62.9% males, 12.3% fatal). Acute myocardial infarction was most frequent in winter and least in summer (P < .0001). The highest number of cases was recorded in January and the lowest in July (P < .0001). Chronobiologic analysis showed winter peaks for total cases (January, P = .035), females (December, P = .009), and fatal cases (January, P < .001). Acute myocardial infarction was most frequent on Monday and least on Sunday (P < .0001). Comparing observed vs expected events, there was a significantly higher frequency of cases on weekdays and reduced on weekends, for total (P < .0001), nonfatal (P < .0001), and fatal cases (P = .0001).

Conclusions

This study confirms a significantly higher frequency of AMI admissions in winter and on a Monday. No difference in the frequency of nonfatal vs fatal events, depending of patients' admissions on weekdays or weekends, was found.

Introduction

Convincing evidence indicates that acute cardiovascular events are not randomly distributed over time but show seasonal, weekly, and circadian patterns. Morning hours, for example, exhibit a higher frequency of cardiac arrests; acute myocardial infarction (AMI) and sudden death; stroke; rupture or dissection of aortic aneurysms; and pulmonary embolism [1], [2], [3], [4], [5], [6], [7], [8], [9], [10], [11]. Several unfavorable mechanisms, all peaking in the morning hours, may play a triggering role [12], [13]. In addition to circadian aspects, seasonal and weekly patterns have been also observed. Winter months show a higher frequency of onset of AMI, stroke, aortic rupture or dissection, and pulmonary embolism [14], [15], [16], [17], [18], [19], [20]. Again, a Monday preference has been reported for AMI and stroke [21], [22], [23]. The aim of this study was to confirm the existence of a seasonal or weekly pattern in the large number of AMI cases referred to the database of the Emilia-Romagna region of Italy and to verify whether a difference is observed between nonfatal and fatal cases.

Section snippets

Methods

The analysis included all consecutive cases of AMI hospitalized between January 1998 and December 2006, according to the regional database of total hospital admissions, Center for Health Statistics, region Emilia Romagna, Italy. Emilia Romagna is a region of northeastern Italy, with a total surface area of 22 134 km² and a total population of about 3 985 000 (≈7% of the entire population of Italy as a whole). Starting from 1998, the Emilia-Romagna database collects all the discharge hospital

Results

During the considered period, the RER database included 64 191 patients with the ICD-9-CM codes for AMI (40 386 males, 62.9%, mean age of 68 ± 13 years; 23 805 females, 27.1%, mean age of 71 ± 11 years) (P < .001). There were 56 268 nonfatal (87.7%) and 7923 fatal cases (12.3%). As for season, AMI was most frequent in winter (n = 16 625, 25.9%) and least in summer (n = 14 486, 22.6%) (P < .0001) (Fig. 1). Table 1 shows data for groups by sex and clinical outcome: nonfatal or fatal. The seasonal

Limitations

The main limitation of this study is its retrospective design and analysis of information obtained from ICD-9-CM codes. All large regional or national databases are subject to common data quality in administrative data sets that rely on physician documentation and coder reliability, including errors in diagnostic coding, missing codes, absence of clinical nuances, and lack of notation for whether the diagnosis was present on admission [26]. However, because coding for AMI results in a high

Discussion

Emergency physicians are aware that the risk to face certain diseases is not the same during the day since different types of emergency calls show distinct circadian patterns [27]. Morning hours, for example, exhibit a higher frequency of AMI and stroke [28], [29], and requests for helicopter transport of cardiac patients show a striking circadian variation not observed in noncardiac patients [30]. Moreover, it seems that morning hours are characterized by a higher frequency of fatal cases [31]

Conclusions

Quoting a recent N Engl J Med editorial [61], emergency physicians better suite the definition of weekend warriors. In fact, with the only exception of the emergency departments, the intensity of medical care on weekends surely does not match that provided on other days of the week. Contrary to recent observations, the present study did not show differences in the frequency rate of monthly or weekly hospitalization of nonfatal and fatal AMI. These results may depend also on different features

Acknowledgments

The authors appreciate the data collection help from Dr Franco Guerzoni and Dr Nicola Napoli, from the Health Statistic Center, Azienda Ospedaliera-Universitaria, Ferrara, Italy.

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^☆: This study was supported, in part, by a scientific grant “Finanziamento per ricerca locale-FAR” from the University of Ferrara, Italy.

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Brief ReportSeasonal and weekly patterns of hospital admissions for nonfatal and fatal myocardial infarction☆

Abstract

Objective

Methods

Results

Conclusions

Introduction

Section snippets

Methods

Results

Limitations

Discussion

Conclusions

Acknowledgments

Am Heart J

J Thorac Cardiovasc Surg

Lancet

J Am Coll Cardiol

Am J Emerg Med

Am J Med

Am J Emerg Med

Am J Cardiol

Ann Emerg Med

Am J Emerg Med

Am J Emerg Med

Thromb Res

J Vasc Surg

Am J Cardiol

Am J Cardiol

Am J Hypertens

Am J Emerg Med

Am J Med

Am J Med

Prospective evidence of a circadian rhythm for out-of-hospital cardiac arrests

JAMA

Circadian variation in the frequency of onset of acute myocardial infarction

N Engl J Med

Circadian variation in the frequency of onset of sudden cardiac death

Circulation

Morning increase in onset of ischemic stroke

Stroke

Circadian variation in onset of ischemic stroke is independent of patients' demographic and clinical features

Arch Neurol

Circadian variability in hemorrhagic stroke

JAMA

Chronobiological patterns of acute aortic dissection

Circulation.

Sudden death from pulmonary thromboembolism: chronobiological aspects

Eur Heart J

From a static to a dynamic concept of risk: the circadian epidemiology of cardiovascular events

Chronobiol Int

Relationships of the circadian rhythms of thrombotic, ischemic, hemorrhagic, and arrhythmic events to blood pressure rhythms

Ann N Y Acad Sci

Seasonal variation in onset of myocardial infarction—a 7-year single-center study in Italy

Chronobiol Int

Brief Report
Seasonal and weekly patterns of hospital admissions for nonfatal and fatal myocardial infarction☆