Temporal Pattern Of The Incidence Of Stroke And The Effects Of Meteorological Factors In Laiwu

Background and objectiveStroke is the main disease leading to death and disability worldwide,and China is one of the countries with the highest incidence of stroke all over the world.It is imperative to investigate the prevention and therapy strategies so as to decrease the burden on family and society.Many risk factors result in the incidence of stroke,however,few studies has focused on the induction factors of stroke incidence.Climate change has adverse impact on human health,especially cerebrovascular disease.Common risk factors known for stroke are hypertension,smoking,abdominal obesity,diet,heart diseases and lack of physical activity and so on.The above risk factors are in a relatively stable state for individuals,while meteorological factors are different from day to day and in a state of continuous fluctuation.Previous studies have proven that the incidence of stroke varies with month,week and season,that climate factors such as air temperature,temperature variation,diurnal range,air atmospheric pressure,relative humidity and wind speed affect the morbidity and mortality of stroke.Physiological processes related to weather changes may trigger acute stroke events.Previous studies have also found that both age and gender affect stroke morbidity and mortality,that the relationship between environmental factors and stroke is affected by age and gender.The conclusions of present studies are inconsistent,and the possible cause may be related to the differences of classifications of stroke,demographics characteristics and district heterogeneity.No researches have been administrated in Laiwu.The present research aimed to investigate the temporal pattern of the incidence of cerebral infarction(CI),intracranial cerebral hemorrhage(ICH),transient ischemic attack(TIA)and subarachnoid hemorrhage(SAH),to illuminate whether the incidence of above stroke types vary on month,week,season and year,and the incidence patterns of different sex and age groups,to discover the potential high risk population of stroke.On this basis,to investigate the effects of climatic factors on different stroke types and discover the potential climate inducements influencing the incidence and death of stroke,and provide theoretical foundation for stroke prevention strategies for regions with similar climate conditions.Methods1.Study population:Inpatients with stroke aged 18 years old and above from the emergency,neurology,neurosurgery and ICU departments of the people's hospital of Laiwu.2.Study data:From January 1,2011 to December 31,2016,the endpoint was the occurrence of stroke events,and the main outcomes were CI,ICH,TIA and SAH.Clinical data were abstracted from health-record management system.Then we arranged the patients according to the time of onset,calculated the total daily,weekly,monthly,seasonal and annual incidence of each stroke type,the male and female incidence,and incidence of each age group.After establishment of the incidence data bank,the monthly,weekly,seasonal and annual differences of each stroke type,including the incidence of different age groups and genders,as well as the distribution characteristics of the length of hospitalization and death cases were analyzed.The meteorological data were obtained from meteorological bureau,and were arranged in chronological order,including daily mean temperature,daily maximum temperature,daily minimum temperature,24-hour variable temperature,daily temperature range,daily mean air pressure,daily average relative humidity and daily average wind speed.The monthly meteorological data included the monthly mean temperature,monthly mean maximum temperature,monthly mean minimum temperature,monthly mean atmospheric pressure,monthly average relative humidity and monthly average wind speed.The correlation and regression analysis of daily and monthly meteorological factors with the number of stroke cases in the same period were analyzed.Results1.The overall distribution characteristics of the incidence of stroke types1.1 The monthly distribution characteristics of the incidence of stroke types:The incidence of CI varied monthly,highest in March,followed by April;lowest in November and December,followed by September,August and July.The incidence of ICH varied monthly,highest in November,followed by October and January;lowest in June,followed by July.The incidence of TIA varied monthly,highest in October,followed by November;lowest in February,followed by May.The incidence of SAH varied monthly,highest in November,followed by January;lowest in July,followed by September.The incidence of each stroke type varied monthly.1.2 The weekly distribution characteristics of the incidence of stroke types:The incidence of CI varied weekly,highest on Monday,followed by Friday,lowest on Sunday,followed by Saturday.The incidence of TIA varied weekly,highest on Wednesday,followed by Friday;lowest on Saturday,followed by Sunday.The incidence of ICH and SAH didn't vary weekly.1.3 The seasonal distribution characteristics of the incidence of stroke types:The incidence of CI varied quarterly,highest in spring,followed by winter;lowest in autumn.The incidence of ICH varied quarterly,highest in autumn,followed by winter;lowest in summer.The incidence of TIA and SAH didn't vary quarterly.1.4 The annual distribution characteristics of the incidence of stroke types:The incidence of CI varied annually,highest in 2013,lowest in 2014.The incidence of ICH varied annually,highest in 2013,lowest in 2011.The incidence of TIA varied annually,highest in 2016,lowest in 2011.The incidence of SAH varied annually,highest in 2015,lowest in 2011.The incidence of each stroke type still showed an overall increasing trend.2.Distribution characteristics of the incidence of stroke types with different age groups:The incidence of ICH varied monthly for age groups,patients younger than 65 years old had higher morbidity than patients aged 65 years old and above.The incidence of CI varied annually for age groups,patients aged 65 years old and above had higher morbidity than patients younger than 65 years.The incidence of TIA varied annually for age groups,patients younger than 65 years old had higher morbidity than patients aged 65 years old and above.There was no significant difference in the incidence of SAH for age groups.3.Distribution characteristics of the incidence of stroke types with different genders:Only the incidence of CI varied quarterly for gender groups,male group had higher morbidity than female group.4.Distribution characteristics of the incidence age of stroke types:Only the incidence of CI varied yearly for age,the average age of onset was highest in 2016 and lowest in 2014.5.Distribution characteristics of stroke types with length of hospitalization:The length of hospitalization of CI and ICH varied monthly,quarterly and annually.The length of hospitalization for CI was the longest in May and June,and the shortest in January and November.The length of hospitalization for CI in spring and summer was longer than that in autumn and winter.The length of hospitalization for ICH was the longest in November,followed by October,and the shortest in May and July.The length of hospitalization for ICH was the longest in autumn,and the shortest in summer.The length of hospitalization of TIA only varied yearly.The length of hospitalization of SAH had no any monthly,weekly,seasonal or annual differences.6.Distribution characteristics of death cases of stroke types:The death cases of CI and ICH varied monthly,weekly and annually but not quarterly.The distribution of SAH death cases showed only annual variability.6.1 Distribution characteristics of death cases from CI:The morbidity and mortality of CI in August and July were low,characterized by hot and rainy climate,suggesting that the low incidence was related to high relative humidity,and hot and humid weather was at least not a contributing factor to the incidence and death of CI,or to a certain extent a protective factor.The morbidity and mortality of CI in April were high,characterized by the highest wind speed,suggesting that high morbidity was related to high wind speed,and high wind speed may also increase the risk of mortality.November is autumn month,with the climate characterized by cool,higher mean air pressure.The length of hospitalization was short and the mortality rate was low in November,thus it was speculated that the number of mild stroke patients in November was high,that the mild CI may be related to high air pressure,and the weather with high air pressure may be helpful to reduce the severity of CI and death risk.The influence of low temperature on the mortality of CI may have a temperature threshold,which needs further researches and discussions.6.2 Distribution characteristics of death cases from ICH:The morbidity and mortality of ICH in November was high,and the hospitalization days were long,indicating that November may be a high incidence period for severe ICH patients,that the increase of incidence and death of ICH was related to high air pressure,low humidity and temperature change.The incidence of ICH in June was low and the death cases were the fewest,characterized by hot and rainy climate,indicating that most of the patients in June had mild ICH,that hot and humid weather may be the protective factor for the incidence and death of ICH.The influence of low temperature on the mortality risk of ICH needs further discussions.7.Relationship between the incidence of each stroke type and meteorological factors:According to the correlation analysis of monthly meteorological factors and monthly stroke incidence,and daily meteorological factors and daily stroke incidence,the meteorological factors influencing the incidence of various stroke types had common factors.7.1 The common negative correlation factor of CI was mean relative humidity and the common positive correlation factor was mean wind speed.7.2 The common negative correlation factors affecting the incidence of ICH were the average temperature,maximum and minimum temperature,and the common positive correlation factor was the average atmospheric pressure.7.3 The common positive correlation factor affecting the incidence of SAH was the mean atmospheric pressure.7.4 As hemorrhagic stroke,both ICH and SAH had the same relative meteorological factors:mean air pressure,followed by air temperature.7.5 As ischemic stroke,CI and TIA did not show the same relevant meteorological factors,it was considered to be related to their different pathophysiological processes.ConclusionOur study investigated the temporal pattern of the incidence of stroke and the relationship between stroke incidence and meteorological factors in Laiwu area,providing foundation for further research.In Laiwu the incidence of stroke has certain temporal pattern,and is related to meteorological factors.When climate conditions fluctuate,it is necessary for the government and relevant warning departments in regions with similar climate conditions to timely remind the susceptible population in order to take preventive measures and diminish the adverse effects of meteorological factors on health.The effect of meteorological factors on the incidence and death of stroke is surely not single.There is synergistic effect between meteorological factors and it is subject to other factors such as basic diseases,the cultural characteristics and the prevention and first-aid system,etc.,which necessitate further and large-scale prospective studies.Our limitation is that the population in this study is relatively small,so the results may not be applicable to different regions with different climates.It should also be noted that our study did not classify the etiology and severity of stroke,so further studies need to be carried out in a larger population to elucidate the effects of meteorological factors on the incidence of stroke.