Cohort Study On The Risk Factors Of Stroke In Mongolian Population

Objective：To investigate the incidence of stroke and its distribution in Mongolian populationlived in the agricultural and pastoral areas. To explore whether baseline traditional riskfactors and inflammatory and endothelial biomarkers were associated with increasedrisk of stroke. To study whether clustering of risk factors is related to the higher risk ofstroke. So a basis can be provided for the prevention and control of stroke.Subjects and methods：1. Baseline investigation： A cross-sectional survey was conducted between2002and2003in Tongliao City, Inner Mongolia,2589participants aged20years and olderwere recruited from32villages in2adjacent townships. Written informed consent wasobtained for all study participants. They were administered interview using a standardquestionnaire, and the related physical examination and blood samples collection wereconducted by trained staffs.Data on demographic characteristics, family history of hypertension, smoking andalcohol consumption were obtained. Blood pressure, height, weight, waistcircumference and hip circumference were measured for all participants according tostandard methods.Fasting blood samples were taken in the morning and separated in the field, andthen were sent to laboratory under low temperature and frozen at-80℃. Fasting plasmaglucose(FPG), insulin(INS), triglyceride(TG), total cholesterol(TC), high-densitylipoprotein cholesterol(HDL-C), low-density lipoprotein cholesterol(LDL-C),apolipoprotein A1(ApoA1), apolipoprotein B(ApoB), plasma rennin activity (PRA),angiotensin II(AngII), nitric oxide(NO), C-reactive protein(CRP), intercellular adhesionmolecules-1(ICAM-1) and endothelial selectin (E-selectin) were detected for all participants.2. Follow-up surveyIn October2008, August2009, August2010and August2012, follow-up surveyswere conducted for the2589subjects involved in the baseline study. Information ofoccurrence and death of stroke during the time from the baseline to the last follow-upwas collected.3. Statistical analysisExcel software was used to establish a database, and all data was checked afterdata entry for two times. All statistical analyses were conducted using SAS9.1andSPSS13.0statistical software, and a significance level of0.05was used.Results：1. A total of2589participants with a mean age of46.51years old, including1064（41.10%） males and1525（58.90%）females, were included in the analysis. Maleshad higher level of NO、CRP、E-selectin、ICAM-1and Ang II than females at thebaseline.2. During the9.2years follow-up,124new stroke cases occurred,76cases wereischemic stroke and46cases were hemorrhagic stroke, and2cases were stroke ofunknown subtype. The incidence density of stroke was519.11/100000person-years,which were840.89/100000person-years in men and306.12/100000person-years inwomen. The incidence densities of ischemic and hemorrhagic stroke were318.16/100000person-years and192.57/100000person-years, respectively. The incidences ofischemic and hemorrhagic stroke increased with age and follow-up time both in menand women.3. Cox regression analyses for whole study population: the results showed that bothischemic stroke and hemorrhagic stroke were associated with increasing age, male,hypertension, family history of hypertension, pulse pressure and mean artery pressure.Heart rate (every increasing10beats per minute) and smoking were positivelyassociated with ischemic stroke, while not hemorrhagic stroke. Furthermore, smokerswith faster heart rate (≥80beats/minute) were at a higher risk of ischemic stroke,compared with group with heart rate<80/nonsmokers, the hazard ratios (HRs) and 95%CI of group with heart rate≥80/smokers were4.12（2.07-8.17）and2.58(1.23-5.38)，respectively, when unadjusted and adjusted for multivariable. Unadjusted and age-andgender-adjusted HRs of ischemic stroke for CRP were1.90(1.20-3.02) and1.61(1.01-2.55), but HR became statistical insignificant after adjusted formulti-variables.4. Multivariable Cox regression analyses for males and females, respectively: theresults showed that the risk factors for both ischemic stroke and hemorrhagic stroke inmen were somewhat different from that in women. Ischemic stroke was positivelyassociated with age, hypertension, smoking, heart rate (10beats/minute) and ApoA1inmen, the HRs（95%CI）were1.11（1.08-1.43），3.65（1.64-8.11），1.32（1.05-1.67），3.26（1.44-7.38）and2.13（1.08-4.18），respectively. Ischemic stroke was positivelyassociated with age，CRP，LDL-C and TG in women, the HRs（95%CI）were1.11(1.07-1.15)，2.41(1.06-5.49)，2.34(1.02-5.38) and0.22（0.05-0.96），respectively.Hemorrhagic stroke was positively associated with age and hypertension in men, theHRs（95%CI）were1.06(1.03-1.09) and3.31(1.32-8.32)．Hemorrhagic stroke waspositively associated with hypertension and drinking in women, the HRs（95%CI）were28.89(3.79-220.47) and3.96(1.41-11.14).5. Compared with those with0-1risk factor，people with2-3,4,5traditional riskfactors, including hypertension, smoking，drinking, high FPG，dislipidemia, overweightor obesity, and central obesity had higher HRs for ischemic stroke after adjusting forage and gender, the HRs (95%CIs) were2.44(1.095.48),2.59(1.056.39) and3.67(1.489.07), respectively.Conclusions：1. The incidence of stroke was high in the Mongolian population in the study, menhad higher incidence of stroke than women, the incidence of stroke increased with ageand follow-up time. Stroke has become an important disease and public health issuethreaten to the health and live of local Mongolian.2．Women with high level of CRP had an increased risk of ischemic strokeincidence; it suggests that inflammation may play a role in the development of ischemicstroke in women. 3. Coexistence of increased heart rate and smoking increased the risk of ischemicstroke incidence.4. Clustering of traditional risk factors was associated with increased risk ofischemic stroke incidence.