Stroke also known as cerebrovascular accident, acute cerebral stroke, the brain blood circulation disorder caused by vascular disease [1]. is usually divided into two categories: one for hemorrhagic stroke, including subarachnoid hemorrhage and cerebral hemorrhage, accounting for about 80% of stroke; another type of ischemic stroke, including transient ischemic attacks (transient ischemic attack), cerebral thrombosis, cerebral embolism and cerebral lacunar infarction, stroke accounted for about 20%[2]. of stroke are the major disease affecting China's urban and rural residents health, with high incidence, high mortality, high disability rate and mortality rate of stroke with high [3]. characteristics is the first cause of death in China, which causes of death accounted for 22.5%, the death toll is about 2000000 [4]. in China stroke mortality is still growing, in the next 20 years is expected to stroke mortality will increase 1 times, the death toll will reach 2000000 ~400 million [5], a serious threat to human health.
1 basic diseases and causes of stroke
1.1 related concepts
Stroke acute attack is mostly due to the underlying disease, such as cerebral arteriosclerosis and vascular congenital developmental abnormalities, genetic diseases, hypertension, heart disease and diabetes risk factors, coupled with the daily life of a variety of incentives and the occurrence, often with emergent features can be traced back to trigger factors. Incentive is to cause net model is close to the disease end result of all the factors, can also be understood as the disease factors model of recency [7], environment and internal environment of body drastic changes are likely to become the important cause leading to the onset of.
The 1.2 factor is the necessary condition of acute cerebral apoplexy.
It was confirmed by [8] that the disease was not necessarily in the end, even though it was the cause and risk factors. On the other hand, even though it had been implemented for the disease prevention and control measures, it still had a stroke. In the prevention of stroke, the risk factors of stroke can reduce the incidence and mortality of stroke. In fact, it is difficult to prevent the occurrence of cerebral apoplexy by reducing the risk factors. In the daily work, many cerebral apoplexy occurred in some daily activities (after), pay attention to these causes and control or reduce the occurrence and development of incentives. It is important to prevent the occurrence of stroke.
2 stroke inducement research progress
Common causes of stroke include physical activity, emotional factors, diet, temperature change, seasonal turnover, diurnal variation, atmospheric factors and other factors (such as infection, beta blockers, etc.), in recent years, there is growing evidence of the relationship between these incentives and stroke.
2.1 physical activity and stroke
Studies show that habitual physical activity can reduce the risk of stroke [9,10], but isolated physical activity can increase the risk of ischemic stroke [11]. physical activity increased the excitability of the sympathetic nervous system, so that the increase in heart rate, so that the systolic blood pressure surge, the study of [11] in the general physical activity of the risk of stroke in 1 h after the event of low physical activity or rest 2.3 times. Anderson et al found that the risk of hemorrhagic stroke within 2 h after moderate or severe physical activity was 3 times that of the non physical activity in this period of time. Koton and other [13] studies found that the risk of ischemic stroke within 2 h after physical activity was 2 times that of the non physical activity population, but this association was not statistically significant. Physical activity increased the excitability of the sympathetic nervous system, and decreased the excitability of parasympathetic nervous system, which resulted in the changes of blood flow dynamics, increased heart rate and blood pressure, increased the level of blood pressure, and increased the level of blood pressure.
2.2 emotional factors and stroke
Colantonio et al. [15] studies showed that when adjusted for known risk factors, there was no statistical significance of depression symptoms and stroke mortality. But there is a study of [16], which suggests that the incidence of stroke in patients with depressive symptoms after adjustment for possible confounding factors. The incidence of ischemic stroke and hemorrhagic stroke were statistically significant. The incidence of ischemic stroke in the exposed group was 1.45 times that of the non exposed group. The relative risk of death stroke was 1.25 ([13,17]. 1.29 95%CI:), and the relative risk of non fatal stroke was 3.36 (CI:0. 82). It was proved that the emotional factor can increase the risk of stroke by (95% ~8.71 1.92). Guiraud and other [19] studies showed that the occurrence of life events in the first 1 months of stroke had a statistical significance, OR was 2.96 (95% CI: 2.19 ~ 4), the OR value was 2.10 (95%CI: 1.40 ~3. 17), when the risk was 1 weeks.
2.3 diet and stroke
[20,21] found that moderate alcohol consumption has a protective effect on the body. But short of drinking affect stroke risk [22].Mostofsky etc. [22]: a case crossover study found that drinking after 1 h compared with non drinkers have the relative risk of stroke was 2. 3, after drinking 2 h occurred in the relative risk of stroke is 1. 6 degrees, relative risk of drinking after 3 h (born stroke back to baseline levels, drinking after 24 h occurred in the relative risk of stroke is 0. 7 degrees; when adjusting for potential incentives, the relative risk in drinking category had no difference. The mechanism of increasing the acute occurrence of cerebral apoplexy after drinking alcohol may be a large amount of alcohol, which makes the fibrinolytic system damaged -25] [23, increase the activity of [26], increase the blood pressure and heart rate [27], so as to increase the risk of acute stroke. Coffee, especially the coffee containing caffeine, can increase the risk of stroke by increasing the vascular stiffness of [27,28], damaging the endothelium dependent relaxing function of [29] and reducing the protective effect of [30]. Study [31] showed that the relative risk of stroke within 1 h after drinking coffee was 2, drinking tea, cola and stroke was not statistically significant; the risk of ischemic stroke in 1 h after drinking was observed in the daily drinking coffee no more than 1 cups. In a meta analysis, the incidence of stroke in the first 2 h of the stroke was statistically significant [32].
2.4 temperature, seasonal, diurnal variation and stroke
Sudden drop in temperature can make the body blood viscosity changes can be induced by infection, so as to increase stroke risk [33]. Some studies [34,35] show cerebral stroke events and weather conditions (especially in cold) is positive correlation. While some studies show that the relationship between stroke and weather conditions is not clear, although the relationship between stroke and weather conditions is not clear, but most of the positive correlation between the study and the relationship between stroke and weather conditions have a role in the relationship between stroke and weather conditions. The case study of Hong et al. [37] showed that the incidence of ischemic stroke was positively correlated with the decrease of temperature in the first 1 days of stroke. OR 17.4, the value of 1 OR at 5 4[38]., and the -42] [39 in the United States, Europe, Japan and China show that the incidence and mortality of stroke were increased by 40%. 20%~. The mechanism of the high prevalence of winter may be cold to cause sympathetic and parasympathetic dysfunction, capillary contraction, blood pressure rise, small artery spasm, and then make the physical and chemical properties of the blood, such as blood clotting time and blood viscosity increased, so as to become the cause of stroke. There is a meta analysis of [43] found that all types of acute cerebral vascular disease (ischemic, hemorrhagic and transient cerebral ischemia occurred), all in the morning 6 am to noon for the high incidence of time, compared with the incidence of 18 79%. high H
2.5 air pollution and stroke
In recent years, a number of studies on -46] [44 show that air pollution has a positive correlation with stroke mortality or hospitalization. 在脑卒中亚型中，大气污染与缺血性脑卒中之间差异有统计学意义，但与出血性脑卒中之间差异无统计学意义[45,47].其机制可能是出血性脑卒中时脆弱的血管破裂需要很长的时间间隔，因此短期的大气污染对缺血性脑卒中的关联比对出血性脑卒中的关联更强[2].短期大气污染增加缺血性脑卒中危险性的机制已经被揭示，吸入大气颗粒物能使肺泡产生炎症，使血液凝集度增加，从而使心血管事件发生的危险增加[48].颗粒物能增加纤维蛋白原，纤维蛋白原在血液凝集和血小板血栓中发挥着重要的作用[49].空气污染可通过直接损坏血管、诱导血管收缩或高血压和促进动脉粥样硬化等使脑血管更易于破裂[44].二氧化硫（ SO2） 和一氧化碳（ CO） 可使心率增加，从而使脑卒中风险增加[50].O'Donnell 等[51]关于大气污染与脑卒中病例交叉研究显示： 在脑卒中合并糖尿病患者中 PM2. 5与脑 Stroke has a strong statistical significance. The [2] and PM2. 5 concentrations of and NO2 were increased in summer. The risk of ischemic stroke, but it does not increase the risk of hemorrhagic stroke or transient cerebral ischemia.
2.6 other factors and stroke
Other factors such as infections, drugs, etc.. Case control studies have been reported to have been reported for the last 1 weeks of infection, the infection, especially with the upper respiratory tract infection and stroke, have been reported. There were statistically significant findings. There was a statistical significance of the results. There was a statistical significance of the study. The results showed that: there were statistical significance between the patients with respiratory tract infection and stroke. The results showed that: there were statistical significance between the patients with respiratory tract infection and stroke. The results showed that: there were statistically significant. The results showed that: the study showed that: the study of the patients with respiratory tract infection. There were statistically significant. The results showed that: the study showed that: 669 patients with cerebral stroke. The study showed that: 8 patients with cerebral stroke had a statistical significance. The study showed that: 12.2 patients with cerebral stroke. Patients with cerebral stroke. Patients with cerebral stroke. Patients with cerebral stroke. The analysis showed that: 30 patients with cerebral stroke. Patients with cerebral stroke. Patients with cerebral stroke. Patients with cerebral stroke. Patients with cerebral stroke. Patients with cerebral stroke. The analysis showed that: 3.4 patients with cerebral stroke. 2 patients with cerebral stroke. Patients with cerebral stroke. Patients with cerebral stroke. 14 patients with cerebral stroke. 30 patients with cerebral stroke. 4 patients with cerebral stroke. 7.3 patients with cerebral stroke. 90 patients with cerebral stroke. The analysis showed that: 669 patients with the activation of the sympathetic nervous system, and therefore, can block the "trigger" caused by the "trigger". Beta blockers have been demonstrated to reduce the incidence of cardiac events in the early morning of the [55], but it has not been reported to be associated with the decrease of the beta blockers.
3 research methods and their advantages and disadvantages
The etiology and risk factor of existence is long-term, but the incidence of stroke has characteristics of short, acute, visible stroke acute seizures are a from quantitative change to qualitative change in the process. At present domestic research focused on using a case-control [56] in which the relationship between the method of event study and stroke, the incentive system of qualitative and quantitative research is less, lack of in-depth investigation and analysis.
3.1 case crossover study
According to the characteristics of stroke, the study of the cause of the disease in the study of the mechanism of stroke can be used in the case of the case of cross research. In 1991, the American scholar Maclure first proposed a case crossover study. It is a method for studying the effect of short time exposure to acute disease [57]. It can be regarded as a paired design of case control study. The case control study was originally proposed to be applied to the study of myocardial infarction, and it was widely used in the study of myocardial infarction, injury, accident, etc. [7].
Stroke and myocardial infarction have the characteristics of sudden, but the domestic use of case study method to study the cause of acute attack of stroke, foreign research mainly focused on acute attack of stroke and air pollution, physical activity, temperature, temperature, alcohol, coffee, feeling and emotional factors. In the study of air pollution and acute attack of cerebral apoplexy, 7, 3, 5 and 1 D were selected as the control window in the study of air pollution and cardiovascular disease, and 1 D was used as the control window, and the high peak of air pollution can increase the risk of stroke by [58].
Case crossover study is a special case of matched case control study method. If exposure to an acute event is related to a shorter period of time (the case), the occurrence of exposure should be more frequent than that in the control group. Object of study include cases and controls two parts, but two parts of information were derived from the same individual. "In some cases" is defined as dangerous period, the period is before the occurrence of diseases or events for a period of time; "control" is part of the control period, the period is defined through dangerous premature specific cases of a period of time. Cross study comparison of individual risk and control during the period of exposure information were compared to determine exposure risk factors and disease development association and correlation degree [57,60].
3.2 exposure period
In this study, there is an important concept - the effect of exposure period. In the study of the cause of stroke, the exposure effect period is the time of the occurrence of the acute attack of cerebral apoplexy. If there is a delay or retention phenomenon, the effect is not due to the exposure period, but the difference between the minimum delay time and the maximum residence time. The length of the dangerous period should be equal to the length of the exposure period, and the length of the period can be deduced according to the experience of the researchers. According to the existing research, the risk of physical activity was 1 h[11,13], the risk of emotional factor was 1. The risk period of alcohol consumption, drinking coffee and drinking was 1 h[22,31,37], the risk of binge drinking was 2 h[32], and the risk of infection was 90 d[54].
Advantages and disadvantages of 3.3 case studies
Applying case study method to study the cause of stroke, it can make each study object as its own control, and it has many advantages compared with the previous studies. In order to study the cause of stroke, the risk population of cerebral apoplexy has basic disease. If it is difficult to find a control group, it is difficult to implement. Reduce the bias caused by the factors such as age, social and economic factors. Save the sample size, and because it is matching data, in the statistical analysis has a very high efficiency; simple, cost less [59].
However, there are limitations in the application of case crossover design: the information bias, as a result of the exposure to the risk of exposure information may be in the language, the method is different, resulting in false contact. The recall bias, respondents may risk exposure factors within the period of memory is not accurate, underestimate the control period of [62]. in the cases exposed to confounding, case crossover study cannot eliminate the influence of individual factors change with time [7], such as the existence of the situation can be stratified or multivariate analysis method for processing [59]. the reporting bias, because some exposure factors related to personal privacy, the respondents have psychological alert, the results of the survey in the survey distortion, so to fully protect the privacy of respondents [2]. use cases for the study of interdisciplinary research methods induced acute stroke to provide epidemiological evidence for quantitative analysis, and "why acute stroke study the factor to trigger".
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