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Seasonal Stability of the Circadian Rhythm in Patients with Type I Myocardial Infarction
Juan-Carlos Díaz-Polanco1, Carlos Tejada-González1, Amanda Leandro-Barros1
1Department of Cardiology, Hospital Universitario Príncipe de Asturias, 28805 Madrid, Spain.
Insights
The daily pattern of ST-segment elevation myocardial infarction (STEMI) presentation remains consistent throughout the year, unaffected by seasonal changes. This suggests that internal biological rhythms, rather than external seasonal factors, primarily influence STEMI timing.
Area of Science:
- Cardiology
- Chronobiology
- Public Health
Background:
- A known circadian rhythm exists for myocardial infarction (MI).
- Limited data explores the relationship between MI incidence, seasons, and months.
- Understanding these patterns is crucial for public health interventions.
Purpose of the Study:
- To investigate the relationship between ST-segment elevation myocardial infarction (STEMI) presentation and seasonal/monthly variations.
- To analyze the circadian pattern of STEMI and its consistency across different times of the year.
- To determine if demographic factors like sex and age influence STEMI's circadian rhythm.
Main Methods:
- Analysis of STEMI alerts from June 2013 to June 2018 in a large Spanish population.
- Inclusion of patients with identifiable culprit plaque causing type I acute myocardial infarction (AMI).
- Statistical analysis of hourly, monthly, and seasonal event distributions, comparing demographic groups.
Main Results:
- A consistent circadian pattern of STEMI presentation was observed, peaking in the afternoon and lowest overnight.
- No significant differences in presentation time were found based on sex, age, or month (comparing July and December).
- A strong correlation existed between monthly event numbers and diurnal vs. nocturnal occurrences, with diurnal events increasing disproportionately.
Conclusions:
- The circadian rhythm of STEMI presentation is robust and not significantly influenced by sex or age.
- Seasonal variations do not alter the fundamental shape or timing of the STEMI circadian pattern.
- The findings suggest that internal biological rhythms, rather than external seasonal triggers, are primary drivers of STEMI timing, with diurnal periods being more vulnerable.
Background:
A circadian rhythm of myocardial infarction has been described but there is little data on its relation with seasons and months.
Methods:
From June 2013 to June 2018, we analyzed the alerts for acute ST-segment elevation myocardial infarction (STEMI) in a Spanish region with 6.64 million inhabitants, universal health coverage, and an organized STEMI reperfusion network. We selected those patients which an identifiable culprit plaque.
Results:
We recruited 6765 cases of STEMI due to type I acute myocardial infarction (type-I AMI), with mean age of 63.2 years (range 17-101, standard deviation [SD] 13.7), 5238 were males (77.4%) and 2801 (41.9%) were 65 years or older. The hourly distribution followed a fixed pattern in all months, with most of the events occurring between 6:00 AM and 4:00 PM, a peak at approximately 01:00 PM and a valley between 10:00 PM and 06:00 AM. No significant difference was found when comparing the mean time to first medical contact between July (the month with more daylight hours) and December (the month with shortest days). No significant differences were found between male and female patients, or between patients aged 65 years or older and younger patients. There was a close correlation between the number of events per month and the number of events occurring during the day (6 AM to 6 PM, r = 0.988, p = 0.001) and during the night (6 PM to 6 AM, r = 0.944, p 0.001), with different slopes of the regression lines (t-test, p 0.001), so that the difference between day-night occurrences increased with the total incidence.
Conclusions:
There is a circadian pattern in the presentation of STEMI that is not influenced by sex and age. The different incidence of STEMI at different times of the year does not affect the circadian pattern in terms of the shape of the curve or the mean time of presentation, although diurnal events increase more than nocturnal events, suggesting that triggers are most likely to act during vulnerable periods as determined by a circadian-based rhythm.
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