Introduction
Acute aortic dissection (AAD) is a medical emergency with the characteristics of sudden occurrence and rapid progression. The results of previous studies have shown that the incidence of aortic dissection is related to hypertension, atherosclerosis, aneurysms, Marfan syndrome, aortic valve deformities, and previous aortic surgery history, which are risk factors for aortic dissection [
1,
2]. Congenital connective tissue defects and pregnancy are also associated with the onset of aortic dissection [
3]. Studies have found that environmental factors have a significant effect on the incidence of cardiovascular events [
4‐
6]. The occurrence of aortic aneurysm rupture, acute myocardial infarction, cerebrovascular accidents and so on is related to climate change, but there is little research on the relationship between the occurrence of aortic dissection and climate change, especially in terms of Chinese data [
7‐
9]. Payman’s research stated that they could not reveal any dependence of atmospheric pressure, air temperature or the presence of a full moon on the incidence of different types of AAD [
10]; however, the correlation between AAD and meteorological conditions and whether the incidence is concentrated is still controversial. We used data from patients with AAD treated in our hospital in the past 7 years, combined with the same period of meteorological data in Fuzhou district, and observed and discussed the possible correlation between meteorological factors and the occurrence of AAD.
Discussion
AAD is not a rare cardiovascular emergency. Howard et al. conducted a survey in Oxfordshire, England, from 2002 to 2012. The results showed that the incidence of AAD was 4–7 per 100,000, and the prehospital mortality rate was as high as 18%. A total of 47.4% of patients with Stanford A aortic dissection and 13.3% of patients with Stanford B aortic dissection died within 30 days [
13]. A survey of Chinese medical insurance research data showed that the hospitalization rate of AAD was 2/100,000, the estimated annual incidence of AAD was 2.8/100,000, and the overall patient mortality rate was 13.9% [
14].
The clinical manifestations of AAD patients are complicated. Most patients die within hours to days after the onset of this disease. If appropriate treatment is administered immediately, the hidden danger of aortic rupture and the restoration of aortic blood supply can significantly reduce overall hospital mortality [
15]. Therefore, studying the incidence of AAD, early detection and timely diagnosis are particularly important to reduce mortality in AAD patients. Mehta et al. analyzed international aortic registration study data and found that cold and temperate winters in the Northern Hemisphere were the peak periods of aortic dissection, and they believed that relative temperature might be a factor affecting the incidence of aortic dissection [
16]. The seasonal volatility of aortic dissection has also been confirmed in related studies in many other countries [
17‐
19].
We analyzed the onset time of 2004 patients with AAD in Fujian Province admitted to our hospital from 2013 to 2019. Aortic dissection was found to have a distinct seasonality. The winter was the peak season, and the number of cases was the lowest in summer. The number of cases was highest in January and lowest in July. The results of the study also suggested that the incidence of aortic dissection increased as the average minimum temperature, average maximum temperature and average daily temperature differences decreased, while the average air quality was not closely related to the occurrence of aortic dissection.
Guidelines for the diagnosis and treatment of aortic diseases issued by the European College of Cardiology recommend that all cases of suspected AAD should be predicted based on the condition, symptoms and clinical manifestations of the patients [
20]. Studies on the correlation between aortic dissection and temperature need to be combined with studies of the characteristics of local meteorological conditions. For example, the results of Benouaich’s study only represented the relationship between the Mediterranean climate and the incidence of AAD in Toulouse [
21]. Fujian is located on the southeastern coast of China in tropical and subtropical regions. The climate is a subtropical marine climate, with a high temperature, high humidity, long-term sunlight, and a large amount of solar radiation. The spring and autumn are short, and the winter and summer are long. The daily temperature difference is smaller than that in northern China. Exploring the impact of meteorological conditions on the incidence of AAD in the coastal areas of southeastern China is also of great significance for the early prediction and early diagnosis of AAD in such regions.
This study analyzed the distribution trend of AAD by using the circular distribution statistical method and obtained the following results. The incidence of AAD had a peak period, and the peak period was from January 13 to 14 each year. The distribution of AAD incidence in different months showed that January had the peak incidence of AAD, followed by December. This study indicated that February had the lowest average minimum temperature, followed by January. Traditional Chinese Spring Festival was in February, all Chinese people would have a long term holiday and there was a lot of population mobility. For example,the city where our hospital located would lose three-quarters of its population over this period. According to the traditional Chinese concept, during this period, patients’ willingness to seek medical treatment was low, and due to the influence of traffic and other factors, the rate of patients visiting provincial cities was low, while visiting the local hospitals was high. Maybe the actual incidence rate of AAD in February was higher, but that didn’t show up in our hospital records. The month with the highest incidence of AAD was basically consistent with the temperature trough, which was similar to Mehta and his team’s finding [
16]. In cold months, people were prone to respiratory infections. As a cause of cardiovascular events, respiratory infections increased the incidence of cardiovascular events, including AAD, especially in patients with basic cardiovascular diseases. In addition, it was easier to consume a high-salt and high-fat diet in winter, while at the same time drinking more, which increased the possibility of cardiovascular disease. The results also suggested that the average minimum temperature, average maximum temperature and average daily temperature differences in the “with AAD day” were lower than those in the “without AAD day”, which proved that AAD was more likely to occur when the average temperature was low.
The results regarding the incidence of AAD in different temperature ranges indicated that the number of AAD cases in the lowest average minimum temperature group was not the largest, and the number of AAD cases in each group did not show an increasing trend with the decrease in average minimum temperature, which seemed to be contrary to Benouaich’s and other studies’ conclusions that the decrease in atmospheric temperature was the cause of AAD [
21]. This might be due to the subtropical and tropical marine climate in Fujian Province, where the base temperature was higher than that of the Mediterranean climate studied by Benouaich et al. However, it could be found that with the decrease in the average minimum temperature, the number of AAD patients with hypertension increased gradually. Hypertension, as the most important susceptibility factor for AAD, might be related to the distribution of AAD in different months [
22,
23]. The systolic and diastolic blood pressures of hypertensive patients were negatively correlated with ambient temperature [
24]. Previous research has confirmed that low temperature is an important stressor of hypertension, leading to higher blood pressure in winter than in summer, and this trend is related to the decrease in winter temperature [
25,
26]. In winter, the temperature is low, the sympathetic nervous system of the human body is activated, and catecholamine secretion is increased to cope with low temperature, which leads to increased heart rate and peripheral vascular resistance, resulting in increased blood pressure. The cold environment promotes the occurrence of high blood pressure, and by increasing blood friction against the vascular wall and surface shear stress, high blood pressure increases the risk of occurrence and rupture of aortic dissection in patients with a history of hypertension [
21].
Benouaich et al. confirmed that the average temperature, maximum temperature, and minimum temperature from 3 days before the onset of AAD to the day of AAD onset decreased significantly, and the daily temperature differences were statistically significant, suggesting that dramatic changes in temperature might have an impact on the incidence of AAD [
21]. This study analyzed the effects of average minimum temperature, average maximum temperature and average daily temperature differences on the onset of AAD over several days. The results showed that the average maximum temperature and average minimum temperature showed a downward trend from 5 days to 2 days before the onset of AAD, and the average daily temperature difference showed a downward trend from 5 days to 3 days before the onset of AAD. The decrease of temperature might have some influence on the occurrence of AAD. However, there was no significant difference in the average minimum temperature, average maximum temperature, or average daily temperature difference from 5 days before the onset of AAD to the day of AAD onset, which suggested that there was no clear correlation between daily temperature changes and the onset of AAD.
Most cardiovascular diseases, such as supraventricular tachycardia, myocardial infarction, ruptured abdominal aortic aneurysm, and subarachnoid hemorrhage, also have a similar seasonality of incidence as aortic dissection [
27‐
30]. Low temperature might be used to increase the likelihood of AAD in patients with cardiovascular disease. Cold weather and high blood pressure are related to the incidence of AAD, which might originate from primary diseases such as hypertension, and atherosclerosis might also worsen due to low temperature. Therefore, for patients with high risk factors of aortic dissection, more attention should be paid to keeping warm and controlling hypertension during seasonal changes to reduce the risk of AAD.
This study was a single-center retrospective study with a limited sample size, different regions, different climatic conditions, different ethnic groups and other factors might lead to different conclusions. Moreover, there was a certain data selection bias, and some data might be missing due to the failure to cover out-of-hospital deaths. The meteorological bureau of our province could not provide the daily air quality data from January 2013 to December 2015. We excluded some aorto-related underlying diseases in the study, which might also have influenced the results. In the future, it would be possible to study the relationship between climate and patients with these diseases. The conclusions of the study still need to be further confirmed by large-scale multicenter studies. We also hope to accumulate more comprehensive registration data for patients with AAD in the future and to further explore the relationship between the incidence of AAD and climate change.
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