Elsevier

American Heart Journal

Volume 189, July 2017, Pages 85-93
American Heart Journal

Clinical Investigation
Seasonal and circadian variations of acute myocardial infarction: Findings from the Get With The Guidelines–Coronary Artery Disease (GWTG-CAD) program

https://doi.org/10.1016/j.ahj.2017.04.002Get rights and content

Background

Seasonal variation with winter preponderance of myocardial infarction incidence has been described decades ago, but only a few small studies have classified myocardial infarction based on ST-segment elevation. It is unclear whether seasonal and circadian variations are equally present in warmer and colder regions. We investigated whether seasonal and circadian variations in acute myocardial infarction (AMI) are more prominent in colder northern states compared with warmer southern states. We also investigated the peak time of admission to better understand the circadian rhythm.

Methods

Data from the GWTG-CAD database were used. We analyzed 82,971 consecutive acute myocardial infarction (AMI) patients treated at 276 US centers from 2003 to 2008. The country was geographically divided into warmer southern and colder northern states using latitude 35 degrees for this purpose.

Results

Overall, acute myocardial infarction (AMI) admissions varied across seasons (P < .01), and were higher in winter (winter vs. spring n = 21,483 vs. 20,291, respectively). When stratified based on type of AMI, non–ST-segment elevation myocardial infarction (NSTEMI) admissions varied across seasons (P < .01) and were highest in winter and lowest in spring. Seasonal variation was not significant in STEMI admissions (P = .30). Seasonal variation with winter predominance was noted in AMI patients in warmer southern states (P < .01), but not in colder states. The distributions of length of stay for AMI patients and door to balloon times for STEMI patients were minimally different across all four seasons (P < .01) with longest occurring in winter. Most patients with AMI presented during daytime with a peak close to 11 am and a nadir at approximately 4 am.

Conclusions

Seasonal variation with winter predominance exists in AMI admissions and was significant in NSTEMI admissions but not in STEMI admissions. Seasonal variation was only significant in warmer southern states.

Section snippets

Background

Acute myocardial infarction (AMI) is one of the leading causes of mortality in United States and worldwide.1 Seasonal variation with winter preponderance of myocardial infarction incidence has been described as early as 1937.2 Since then, multiple studies have demonstrated the chronobiology of myocardial infarction in different contexts,3., 4., 5., 6. but only a few small studies have classified myocardial infarction based on ST segment elevation.7., 8., 9. Some studies report higher incidence

Methods

We used GWTG-CAD, which is a hospital based quality improvement initiative which involved about 1800 hospitals representing >75% of myocardial infarction patients in the United States.19 Hospital participation in the program is voluntary and it includes hospitals from all regions, academic and community hospitals and urban and rural hospitals. Participating hospitals collect pertinent clinical information including demographics, medical history, diagnosis, investigation results, in-hospital

Results

We included 82,971 patients enrolled in GWTG-CAD registry based on our inclusion criteria described earlier. Out of these, more hospital admissions occurred in winter (n = 21,483), while spring (n = 20,291), summer (n = 20,543) and fall (n = 20,654) had similar admission rates. Baseline characteristics of the admissions that occurred in different seasons are given in Table I. Overall the mean age of our study population was 67.5 years, 60% were male and 74.5% were white. Although many of the

Discussion

Our results demonstrated four main points. First, there is seasonal and circadian variation in myocardial infarction. This seasonal variation was prominent in NSTEMI admissions without a statistically significant difference in STEMI admissions. Second, winter predominance in acute myocardial infarction was seen mainly in warmer southern states and was not statistically significant in northern colder states. Third, hospital admissions for AMI peaked close to 11 am in the morning with a nadir

Conclusions

Seasonal variation with winter predominance was observed in AMI admissions in this large national registry. Similar effect was seen in NSTEMI admissions, but there was no statistically significant variation in STEMI admissions. Circadian variation was seen in both NSTEMI and STEMI populations with a peak at approximately 11 am and a nadir at approximately 4 am. When stratified by regions, seasonal variation was observed predominantly in warmer southern states and was not significant in colder

Source of funding

The study was supported by a grant from American Heart Association. Data collection and management were performed by Outcome, Inc. (Cambridge, MA). The analysis of registry data was performed at Duke Clinical Research Institute (Durham, NC), which also receives funding from the American Heart Association. The sponsor was not involved in the management, analysis, or interpretation of data or the preparation of the manuscript.

Disclosures

V. Nagarajan – None.

Gregg C. Fonarow – None.

Christine Ju – None.

Michael Pencina – None.

Warren K. Laskey – None.

Thomas M. Maddox – None.

Dr. Deepak L. Bhatt discloses the following relationships - Advisory Board: Cardax, Elsevier Practice Update Cardiology, Medscape Cardiology, Regado Biosciences; Board of Directors: Boston VA Research Institute, Society of Cardiovascular Patient Care; Chair: American Heart Association Quality Oversight Committee; Data Monitoring Committees: Duke Clinical

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    W. Douglas Weaver, MD served as guest editor for this article.

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