Introduction
Due to the improvement of health systems and increase in life expectancy, the population of older people is increasing [1]. These changes lead to an increase in the burden of cardiovascular diseases and their related costs [4]. In high-income countries, the burden of heart diseases has decreased mainly due to health improvements, while in low-income countries this burden has remained high [12]. ST-segment elevation myocardial infarction (STEMI) is a common and serious type of myocardial infarction with high morbidity and mortality [7]. There is little information about the management and risk factors of STEMI affecting the long-term mortality of older people in low- and middle-income countries [14]. The aim of this study is to evaluate the risk factors, clinical characteristics, and treatment patterns of STEMI and to examine the predictors of one-year mortality in older patients with STEMI in western Iran.

Methods
This retrospective cohort study was conducted on 421 older people (≥65 years) with STEMI admitted to Imam Ali Hospital in Kermanshah, Iran, from July 3, 2018, to December 21, 2019. After admission, patients’ contact information was recorded. Trained doctors and nurses collected the demographic and clinical information of the patients through standard questionnaires and medical records. The variables examined in this study included age, gender, body mass index (BMI), level of education, place of residence, low-density lipoprotein (LDL), high-density lipoprotein (HDL), glomerular filtration rate (GFR), diabetes, blood pressure, chronic kidney disease, history of smoking, history of coronary interventions, history of cardiovascular events, type of heart attack, type of treatment (PCI, thrombolytic treatment and no treatment) and left ventricular ejection fraction (LVEF). The primary outcome of the study was 1-year mortality after STEMI.
Patients were followed up for one year. Trained nurses called the patient’s family or companions and invited the patient for re-examination. In case of death, the date is recorded based on the death certificate or the statements of the family of the deceased patients. Survival time was considered from the date of admission to death, and if the patient survived 365 days after admission. To describe continuous variables with normal distribution, Mean±SD was used. For abnormal cases, median and interquartile range (IQR) were used. The classified variables were expressed by frequency and percentage. To identify predictors of one-year mortality, Cox proportional-hazards model was used in univariate and multivariate form. Variables with a significance level <0.2 were added to the multivariate model. Data analysis was done in Stata software, version 12.

Results
Participants were 421 older people with STEMI. The follow-up period was 350.62 person-years. In the one-year follow-up, it was not possible to contact 9 people (missing rate: 2.1%). The one-year mortality rate was (n=76[18.5%]), of which 9.3% patients (n=39) died in the hospital. The majority of patients were male (67.5%) and residents of Kermanshah City (74.9%). The mean age of patients was 73.51±6.73 years; (n=264[62.7%]) had a history of hypertension, (n=230[54.9%]) had chronic kidney disease, (n=103[24%]) had a history of diabetes, and (n=103[24.5%]) had a history of smoking. In terms of education, 239(60.8%) were illiterate, 136(34.6%) had elementary school up to high school education, and 18 (4.6%) had a high school diploma or higher. The LVEF for 130 patients (35%) was <35%, 35-50% for 55% of patients, and >50% for 50% of patients. Overall, 212 patients (50.4%) had received PCI, 128(30.4%) thrombolytic treatment, and 81(19.2%) did not receive reperfusion. Of 76 patients (18.5%) who died, 12.4% had undergone PCI, 16.1% had thrombolytic treatment and 0.38% had not received any reperfusion treatment. 
Based on the results of univariate Cox proportional-hazards model, lack of reperfusion treatment was one of the risk factors for one-year mortality in the elderly with STEMI (P<0.05). For every one year increase in the age, the risk of one-year mortality by STEMI increased by 1.05 times. Higher GFR and educational level were protective factors for death in the elderly. The results of multivariate Cox model showed that higher GFR and lack of reperfusion treatment had a statistically significant relationship with one-year mortality (P<0.05). For every one unit increase in GFR, the one-year mortality rate decreased by 3%. Also, the one-year mortality rate of the elderly who received reperfusion treatment decreased by 51% (P<0.05) (Table 1).



Conclusion
In this study, the majority of older patients with STEMI had been treated with PCI, and their one-year mortality rate was lower than those who received thrombolytic therapy. Older age, decreased GFR, lower literacy level, and lack of reperfusion therapy were associated with an increased risk of one-year mortality in the patients. Creating a management and treatment network for STEMI patients and planning to improve the health literacy of these patients through educational interventions about the symptoms of STEMI and the importance of timely treatment can be very effective in improving clinical outcomes.

Ethical Considerations
Compliance with ethical guidelines
This study was approved by the Ethics Committee of Kermanshah University of Medical Sciences (Code: KUMS.REC.1395.252).

Funding
This study was funded by Kermanshah University of Medical Sciences (Grant No.: 1395.252).

Authors' contributions
The authors contributed equally to preparing this article.

Conflicts of interest
The authors declare no conflict of interest

Acknowledgements
The authors would like to thank all participants, the personnel of Imam Ali Hospital in Kermanshah, and the Vice-Chancellor for Research of Kermanshah University of Medical Sciences for their cooperation and support in this study.

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