Study of determinants of long term mortality after stroke In East Azerbaijan, Northwest of Iran, 2014-16

Abstract

Study of determinants of long term mortality after stroke In East Azerbaijan. Background and purpose: Stroke is the second leading cause of adults’ death and disability in most western countries. There is little knowledge of the extent of fatality and the factors affecting long-term mortality following a stroke in Iran, and especially in East Azerbaijan province. The present research was designed and implemented with the aim of investigating the extent of one-year,18-month and two-year mortality following a stroke and the factors affecting it in East Azerbaijan Province. Methods: This study was conducted using a prospective cohort study design in Tabriz, Northwest of Iran. All hospitalised cases in Razi and Emam Reza (referral centres of Tabriz) from October 2013 to March 2015 were included and followed until two years after the onset of the stroke. Patients with first-ever ischemic stroke (Embolic and Thrombotic) and hemorrhagic stroke (Intracerebral Hemorrhage, Subarachnoid Hemorrhage) according to the International Classification of Diseases (ICD-10) system with definitive diagnosis based on CT and MRI scans were included in this study. Census sampling method was used. Following definitive diagnosis of stroke and obtaining the conscious consent of the patient, their data were recorded in a checklist through an interview or using their file by an instructed expert. To measure the severity of the stroke, Modified National Institutes of Health Stroke Scale (mNIHSS) was administered by a neurology resident at the hospital. As a consequence being measured in this study was patient’s death or survival during the follow-up period, Modified Rankin Scale (MRS) was administered by an instructed expert until two years after the incidence of the stroke. To estimate the survival function, Kaplan-MEIER analysis was used, and for between-groups comparison, Log-rank method was applied. To identify factors predicting mortality, semi-parametric Cox regression analysis was used, The data were analysed using STATA software (version 14). A p-value of less than 0.05 was considered as the significance level. Results: A total of 1036 first-ever stroke patients were included in the study.. 852 patients (82.2%) had ischemic stroke, and 184 patients (17.8%) had hemorrhagic stroke. Mean age of patients was 69.09 years with a standard deviation of 12.79 years and 54.6% of participants were male. Regarding comorbid condition 85.8% of the patients suffered from hypertension, 47.8% from diabetes, 27.8% from cardiovascular diseases and 46.9% from hyperlipidemia. Of them 394 (38%) patients died due to stroke within two years, and 24 patients (2.3%) died of causes other than stroke. Most deaths occurred within the first month after the occurrence of the stroke (56.8%). Follow-up was not completed for 64 patients (6.2%). The mortality rate of stroke in one-year,18-month and two- years follow-up periods was 34.5%, 36.5% and 38% respectively. In a univariate analysis, factors such as age, education, BMI, type of stroke, family history of stroke, diabetes, hyperlipidemia and the mNIHSS score had a statistically significant relationship with one-year,18-month and two-year mortality rate. marital status just had a statistically significant relationship with two-year mortality rate. Patients with hyperlipidemia had a lower risk of mortality and hyperlipidemia played a protective role against mortality. In the multivariate Cox model, variables age, type of stroke, diabetes, and severity of stroke according to the mNIHSS index were identified as factors predicting one-year,18-month and two-year mortality following the stroke. As the age increases, risk of one-year,18-month,two-year mortality also increases so that the risk of one year, 18-month and two year mortality in patients of the age group ≥75 years 3.92 (2.04-7.55),3.78 (1.06-6.94) and 3.98 times (2.17-7.29) risk of higher mortality than the age group below 55 years respectively. Having diabetes increases the risk of one-year, 18-month and two-year mortality 1.35(1.03-1.77), 1.38(1.07-1.80) and 1.40 times (1.09-1.81) respectively. Hemorrhagic stroke increased the risk of one-year, 18-month and two-year mortality 1.42(1.03-1.97), 1.45(1.06-1.98) and 1.44 times (1.06-1.97) respectively. As the mNIHSS increases, risk of one-year,18-month,two-year mortality also increases in a way that risk of one-year,18-month,two-year mortality in patients with a mNIHSS≥20 had 14.77 (8.97-24.31), 12.93 (8.13-20.56) and 12.92 (8.20-20.35) times higher risk of mortality than patients with mNIHSS ≤5 respectively. Conclusion: The present research provides useful information about an epidemiologic picture of this disease and factors affecting mortality from stroke in the region. Based on the results of this study, the mortality rate of one year, 18 months and two years was 34.5%, 36.5% and 38% respectively. In Cox multivariate analysis, variables age, type of stroke, the severity of the stroke, and diabetes were main factors affecting two-year mortality.