Exploring the periodicity of cardiovascular events in Switzerland: Variation in deaths and hospitalizations across seasons, day of the week and hour of the day☆,☆☆
Introduction
Seasonality of mortality from cardiovascular diseases (CVD) has been observed and analyzed worldwide. Several hypotheses have been put forward to explain seasonal, monthly, weekly and hourly variations in CVD deaths such as temperature-driven alterations in blood pressure [1], stress [2], thrombotic activity [3], fibrinogen concentration [4] or cholesterol changes in diet [5], [6] but no consistent causality has been proven.
In regards to seasonal or monthly variation, it has been shown that winter months lead to more deaths by AMI and stroke [3], [7], [8] particularly in areas subject to heterogeneous weather throughout the year. In areas with minimal seasonal climatic changes such as Taiwan, there appears to be no such seasonal variation in the incidence of stroke [9]. Many studies have also observed that older patients (≥ 65 years of age) are more influenced by seasonal changes than the younger patients (< 65 years of age) [10], possibly because the temperature extremes affect their thrombotic activity more seriously [3]. Conversely, the summer months usually present the lowest mortality rates from CVD [11], [12].
In regards to the variation according to the day of the week, interesting observations have been found. For instance young men present a stronger weekly variation than their older counterparts, both regarding stroke [13] and AMI [14] mortality. In the younger subgroup, the peak incidence occurred on Mondays for strokes [13] and on Mondays and Saturdays for AMI [14]. This pattern may be explained by work-related stress inducing a release of catecholamines (Blue Monday) or the “weekend warrior phenomenon” by which normally sedative office workers participate in more strenuous physical activities resulting in an increase incidence of sudden death on Saturdays.
Finally, a circadian rhythm has also been noted for all CVD. According to several studies, strokes and AMI are more likely to occur in the morning (6 am–noon) with a second and smaller peak in the afternoon (~ 3 pm) [8], [15], [16], while a nadir has been observed during night hours. This pattern has pushed some authors to put forward prevention strategies [17].
Switzerland is characterized by a low mortality from CVD and also by a consistent season pattern, with large temperature amplitude. Still, to our knowledge, no study has ever focused on the periodicity of CVD mortality, including AMI and stroke in Switzerland. Hence, we used the data from the Swiss mortality database to assess the seasonal, daily and hourly death rates due to CVD, including AMI and stroke. The results were further confirmed by the analysis of hospital discharge data.
Section snippets
Mortality database
Mortality data was provided by the federal office of statistics (www.bfs.ch). The database records all deaths occurring in Switzerland since 1969. The data collected include gender, age at death, main and surrogate causes of death, and date and hour of death. Regarding the hour of death, the information was only available for 1979 onwards. Two international classifications of diseases (ICD) of the World Health Organization were employed: ICD-8 (before 1995) and ICD-10 (after 1994).
For this
Database description
Data from 2,362,430 deaths was analyzed, of which 869,863 (36.8%) from CVD, 361,322 (15.3%) from AMI and 221,972 (9.4%) from stroke. Among CVD deaths, 89.2% occurred in subjects aged over 65 years and 52.3% in women. The corresponding values for AMI were 85.1% and 44.2%, and for stroke 92.8% and 59.0%.
Data from 11,353,651 hospitalizations was analyzed, of which 959,990 (8.5%) from CVD managed on-site. Among patients managed on-site for CVD, almost seven out of ten (69.1%) were aged 65 years and
Discussion
To our knowledge, this is the first study to assess the periodicity of death from CVD in Switzerland. Our results confirm the findings of previous studies conducted in other countries and provide interesting data for a better seasonal and daily planning of the emergency management of CVD.
Conclusion
In Switzerland CVD events and deaths present specific seasonal, weekly and circadian patterns. These patterns appear to be influenced by different factors and their importance varies according to gender and age. This information could be applied to optimize preventive and emergency health resources.
The following are the supplementary data related to this article.
Author contributions
PMV and MR researched the data and wrote the manuscript. FP and HS reviewed/edited the manuscript and contributed to the discussion.
Pedro Marques-Vidal is the guarantor of this work and, as such, had full access to all the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis.
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2017, Heart Failure ClinicsCitation Excerpt :However, the magnitude of the Monday peak was limited. More recently, the Monday preference was confirmed in other studies,8–10 although such excess did not always reach statistical significance. The weekly peak of acute myocardial infarction was detected on the first workday of the week, with a gradually decreasing tendency until the end of the week.
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All authors take responsibility for all aspects of the reliability and freedom from bias of the data presented and their discussed interpretation.
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This study was not funded.