Archives of Academic Emergency Medicine. 2021; 9(1): e35 https://doi.org/10.22037/aaem.v9i1.1157 OR I G I N A L RE S E A RC H Prevalence and Related Factors of Post-Traumatic Stress Disorder in Emergency Medical Technicians; a Cross- Sectional Study Afshin Khazaei1, Maryam Esmaeili2, Habib Masoumi3, Elham Navab4∗ 1. Intensive Care and Management Nursing Department, School of Nursing and Midwifery, Tehran University of Medical Sciences, Tehran, Iran. 2. Critical Care Department, Nursing and Midwifery Care Research Center, School of Nursing and Midwifery, Tehran University of Medical Sciences, Tehran, Iran. 3. Disaster and Emergency Management Department, Hamadan University of Medical Sciences, Hamadan, Iran. 4. Critical Care and Geriatric Nursing Department, School of Nursing and Midwifery, Tehran University of Medical Sciences, Tehran, Iran. Received: February 2021; Accepted: February 2021; Published online: 30 April 2021 Abstract: Introduction: Ongoing exposure to a variety of Pre-hospital Emergencies (PE) has placed Emergency Medi- cal Technicians (EMTs) at serious psychiatric compromise such as Post-Traumatic Stress Disorder (PTSD). The present study aimed to evaluate the prevalence and associated factors of PTSD among EMTs. Methods: This prospective cross-sectional study was conducted on EMTs in the Emergency Medical Services (EMS) in west of Iran. A baseline information questionnaire including personal work-related characteristics and the PTSD check- list of DSM-5 (PCL-5) were used for data collection. Non-parametric tests and multivariate linear regression were used to evaluate the associated factors of PTSD in these participants. Results: Among the participants, 22% of technicians had PTSD-diagnostic criteria. The mean total PCL-5 score was 21.60 ± 11.45, while the scores were 38.02 ± 6.08 and 17.47 ± 8.36 in the PTSD-diagnosed and undiagnosed groups, respectively. The most common symptom of the clusters was negative alterations in cognition with a mean score of 7.42 ± 4.63. After adjusting confounders, the number of missions (t= 2.50, P= 0.013), work experience (t= -3.24, P= 0.001) and number of shifts (t: 26.38, P < 0.001) were significantly corelated with PCL-5 score. Conclusion: The results indicated that the prevalence of PTSD among EMTs personnel of hamadan province is high. EMTs with the age of ≤ 30 years, work experience of ≤ 10 years, married status, informal employment, emergency medical technician’s degree, and more than 8 shifts per month, as well as no previous training history had a higher total PCL-5 score. Keywords: Emergency medical technicians; emergency medical services; diagnostic and statistical manual of mental disorders; stress disorders, post-traumatic Cite this article as: Khazaei A, Esmaeili M, Masoumi H, Navab E. Prevalence and Related Factors of Post-Traumatic Stress Disorder in Emer- gency Medical Technicians; a Cross-Sectional Study. Arch Acad Emerg Med. 2021; 9(1): e35. 1. Introduction Emergency Medical Technicians (EMTs) experience some cu- mulative stress, which may be related to traumatic events (1). In addition, frequent and ongoing exposure to poten- tially traumatic events may place EMTs at higher risk of serious psychiatric compromise, including Post-Traumatic Stress Disorder (PTSD) (2, 3), which is considered as a mental ∗Corresponding Author: Elham Navab; School of Nursing and Midwifery, Nosrat St., Tohid Sq., Tehran, Iran. 141973317. Tel: 00989173110323, Email: e_navab100@hotmail.com health disorder leading to social, occupational, and interper- sonal disturbance (4). The experience of a traumatic event is not the only effective factor causing PTSD among individuals (5). Therefore, iden- tifying risk factors other than exposure to traumatic events, such as personal/work-related characteristics that can pre- dict the development of PTSD, can lead to more effective management and control of prehospital emergency stress in the EMTs. Considering the current overall PTSD prevalence (from 11% to 35%) among EMTs (6, 7), which is the highest rate among prehospital care providers (8), the need for assessing the This open-access article distributed under the terms of the Creative Commons Attribution NonCommercial 3.0 License (CC BY-NC 3.0). Downloaded from: http://journals.sbmu.ac.ir/aaem A. Khazaei and et al. 2 mental health of EMTs and identifying the staff members at high risk of developing PTSD is crucial. Although a large number of studies have examined PTSD in EMTs using DSM-4 tools, little information is available on assessing PTSD by considering DSM-5 criteria in the EMS. Therefore, the present study aimed to evaluate the preva- lence and associated factors of PTSD among EMTs. 2. Methods 2.1. Study design and setting In this cross-sectional study, the data of EMTs in 20 metropolitan-based, 30 road-based, and one air-based ser- vices (serving about two million people) in Hamadan province, Iran, were collected during July-October 2018. All of the EMTs in the Emergency Medical Services (EMS) in this province were invited to participate in this study. Before run- ning the study, the objective of the study was explained to the EMTs. Then, all participants voluntarily signed the consent form and their names and personal information were kept confidential in the questionnaires. The project was approved by the Ethics Committee in Tehran University of Medical Sci- ences (No: IR.TUMS.FNM.REC.1397.042). 2.2. Participants Operational EMTs who worked in urban, road, and air emer- gency bases full-time and gave their oral and written con- sent were included in the presnet study. However, non- operational EMTs, the staff from other medical centers work- ing part-time, and those who experienced non-occupational stressors such as the death of close relatives in the previous eight weeks were excluded. 2.3. Data gathering In order to collect the related data, demographic question- naire (including personal and work-related characteristics) and PTSD Checklist for Diagnostic and Statistical Manual of Mental Disorders-5 (PCL-5), which is regarded as a self- reporting tool that evaluates a variety of purposes such as screening individual for PTSD, were used in this study (10). The PCL5 checklist includes 20 items, divided into four clus- ters including intrusion (5 items), avoidance (2 items), neg- ative alterations in cognition and mood (7 items) and al- terations in arousal and reactivity (7 items). Each item is scored on a 5-point Likert scale ranging from 0 (Not at all) to 4 (Extremely) (10). Furthermore, the reliability and va- lidity of this checklist have been confirmed in some studies (11-13). Although the validity and reliability of the Persian version of this instrument were confirmed through using ex- ploratory and confirmatory factor analyses, convergence va- lidity (r=0.68%, P=0.001), and Cronbach’s alpha (r=0.79%), as well as retesting (r=0.77%) (14), we reassessed the PCL-5 reli- ability (r=0.89) for the total score in this study. 2.4. Statistical analysis In the study conducted by Iranmanesh et al. (9), the re- ported PTSD rate among EMTs was 0.22%. The total num- ber of EMTs was 307, among whom 251 were selected by considering the relative error of 10% and 95% confidence in- terval. Continuous variables were expressed as mean and standard deviation (SD) or median and interquartile ranges (IQRs). Categorical variables were reported in frequency and percentages. The total score of symptom severity was ob- tained by summing the scores related to the 20 items, and ranged from 0 to 80. In addition, a PCL-5 score of less than 33 appears to not require further psychometric work (10, 15, 16). Therefore, scores were dichotomized into scores ≥ 33 (meet- ing the criteria for PTSD) and scores < 33 (not meeting the criteria for PTSD) for screening PTSD symptoms. Kruskal-Wallis and Mann-Whitney tests, as well as multi- variate linear regression (using OLS), were used for assess- ing the correlation and identifying the predictors for PTSD symptoms. Furthermore, interaction and multi-collinearity (Variance Inflation Factor < 10 or Torrance > 0.2) were as- sessed for the regression final model. Adjusted beta coef- ficients were computed based on 95% confidence intervals. Furthermore, model fits were evaluated using Scatterplots, Homoscedasticity, Durbin-Watson test, Normal P-P Plot, Q- Q plot, and Cook’s Distance values. Continuous variables such as age, work experience, number of shifts, and num- ber of missions, and categorical variables such as marital status (single, married, divorced), degree (emergency med- ical technician, nurse, operation room technician, anesthe- sia technician), employment status (formal, informal), base location (urban, road, air) were considered as possible inde- pendent variables of the model. All statistical analyses were performed using IBM SPSS Statistics version 20 and P <0.05 was considered as the significance level. 3. Results In the present study, 259 male EMTs were recruited for par- ticipation in the study after being qualified for the inclusion criteria (figure 1: study flowchart). The mean age of the par- ticipants was 32.79 ± 6.16 years (21 - 52) and their median work experience was 9 years (IQR 5-12). The median number of work shifts and pre-hospital missions in which technicians were deployed in the previous month was 12 (IQR 11-13) and 60 (IQR 9-85), respectively. 53.7% of the EMTs had previous training on stress control and management. PTSD prevalence in the EMTs was 22.00%. The mean age of EMTs in the PTSD-diagnosed group was 28.88 years (SD= 6.94) with mean total PCL-5 score of 38.02 (SD= 6.08), while mean age was 33.77 years (SD= 5.55) and mean total PCL-5 This open-access article distributed under the terms of the Creative Commons Attribution NonCommercial 3.0 License (CC BY-NC 3.0). Downloaded from: http://journals.sbmu.ac.ir/aaem 3 Archives of Academic Emergency Medicine. 2021; 9(1): e35 score was 17.47 (SD = 8.36) in the group without PTSD. The mean total PCL-5 score in all samples was 21.60(SD = 11.45) and ranged from 4 to 50. In addition, the mean total score was 4.98(SD= 3.08), 2.25(SD= 1.70), 7.42(SD= 4.63), and 6.94 (SD= 4.10) for intrusion, avoidance, negative alterations in cognition, and alterations in arousal and reactivity clusters, respectively (table 1). Table 2 indicates the mean of each cluster and the total PCL- 5 score based on personal/work-related characteristics. Furthermore, negative alterations in cognition were regarded as the most common cluster symptom and ranged between a score of 2 (19.7%) to 22 (0.4%) based on intensity (6 items with a score between 0-24). As shown in Table 1, alterations in arousal and reactivity were the second most common symptoms with the score ranging between 2 (18.1%) and 19 (4.0%) (7 items with a score between 0-28). Furthermore, the result of Mann-Whitney test indicated that the difference be- tween mean score of clusters in PTSD and non-PTSD groups was statistically significant (p<0.001). Based on the results, demographic factors such as age (t =41.86, df=2, P<0.001), marital status (t =49.60, df=2, P<0.001) and number of shifts (Z= -6.78, P< 0.001) were significantly associated with PCL-5 score (Table 2). However, no sig- nificant relationship was observed between some factors such as work experience (t =3.01, df=2, P=0.204), number of mission (Z= -1.65, P= 0.098), employment status (Z= -1.07, p=0.282), base location (t =3.84, df=2, P=0.146), degree (t =0.42, df=3, P=0.935), and previous training history status (Z= -0.88, p=0.375) with the total PCL-5 score. After adjusting confounders in multivariate linear regression, the number of missions (t: 2.50, P=0.013) and work experi- ence (t: -3.24, P=0.001) could significantly predict PTSD sta- tus. In this regard, the number of shifts per month was the strongest factor (t: 26.38, P<0.001). Additionally, no violation of assumptions was observed in the regression model. Fi- nally, the linear regression of the final model was significant (f= 297.30, df= 258, P < 0.001), which could explain 77.8% of the variance in the total PCL-5 score (R2 = 0.77). 4. Discussion The present study aimed to screen those with PTSD accord- ing to DSM-5 criteria and identify its related factors among the studied EMTs. PTSD prevalence rate among the studied EMTs was 22.00%. In addition, negative alterations in cogni- tion (M= 7.42) and avoidance (M= 2.25) were the most and least common clusters, respectively. In general, EMTs with the age of ≤ 30 years, work experience of ≤ 10 years, mar- ried status, informal employment, emergency medical tech- nician’s degree, and more than 8 shifts per month, as well as no previous training history had a higher total PCL-5 score. Furthermore, the rate of PTSD among the EMTs in the Figure 1: Study flowchart. EMTs: Emergency Medical Technicians. Figure 2: Simple Box Plot of correlation between base location and total PCL-5 score; Median: number of missions. present study (DSM-5) is considerably high, compared to that of other studies (22). Petrie et al., in their systematic re- view and meta-analysis, showed that the prevalence rate of PTSD (DSM-4) among ambulance staff was 11% (22). Fjeld- heim et al. reported that 94% of paramedic trainees in a South African University were directly exposed to trauma, and only 16% met the diagnostic criteria for PTSD (23). Per- haps, the choice of different instruments and the context are some of the reasons for this variation in the reported preva- lence of PTSD. The number of missions conducted by technicians stationed at the road and air bases was less than that of the urban bases, leading to less exposure to prehospital emergencies; yet, no significant difference was observed in the total PCL-5 score This open-access article distributed under the terms of the Creative Commons Attribution NonCommercial 3.0 License (CC BY-NC 3.0). Downloaded from: http://journals.sbmu.ac.ir/aaem A. Khazaei and et al. 4 among the EMTs stationed at the three above-mentioned bases (P= 0.146) (figure 2). Perhaps, technicians who were stationed at the road and air bases have had more expo- sure to extremely traumatic events and provided high-acuity care in the unstable physical and environmental situations related to these bases such as the long distance between the road base with the first medical center, air turbulences, flight altitude, and the like. Presently, EMS transports those with a life-threatening condition and requiring critical care to a hospital via air bases. They experience more stress because the roads in Iran are considered to have one of the highest rates of accidents in the world and road-based technicians are faced with dangerous accidents leading to more casual- ties and injuries. The results of the present study were in- consistent with those of Schiszler et al., which reported that ground rescue workers are exposed to higher work-related stress compared to the air-ambulance workers (24). Based on univariate linear regression, the number of shifts per month has a strong effect on the PCL-5 score so that the total PCL-5 score in the EMTs increased nearly 0.8% (stan- dardized beta coefficient) in the exchange for doing a shift (24 h). The result is inconsistent with the study of Iranmanesh, which indicated that paramedics who work less than 100 hours per month may have a higher rate of PTSD (P=0.001) compared to those working 100–150 or more than 200 hours per month (9). In this regard, Shift Work Sleep Disorder (SWSD) may be regarded as one of the reasons that can ex- plain the impact of shift work on individuals’ PTSD. SWSD is considered a condition resulting from working atypical shifts including nights and long work hours, such as EMTs’ shifts, leading to the disorder of circadian rhythm and accordingly PTSD symptoms (25, 26). Furthermore, age was considered as another factor, which was significantly correlated with the PTSD score as a categor- ical and continuous variable in the Kruskal-Wallis (P<0.001) and the univariate linear regression ( β=-0.36, t= -3.19, P=0.02) test. However, it was not regarded as a strong inde- pendent predictor of PTSD in the multivariate linear regres- sion analysis. Kerai et al. found a negative relationship be- tween age and PTSD symptoms ( β=0.17, P= 0.03) in the lin- ear regression, which indicates a higher prevalence of PTSD in the younger staff (18). In the present study, the PTSD total score in technicians who were less than 30 years was higher than the score in other age groups (Table 2). Unexpectedly, the total score in the age group of 40 years was higher than that of 31-40 years in the EMT. Thus, age can be a protective factor against PTSD to a certain level, although a gradual in- crease in the exposure to the traumatic events over time, irre- spective of other important factors such as work experience. Based on the results in the study, no significant relationship was observed between work experience as a categorical vari- able and the total PCL-5 score, while work experience had a protective effect against PTSD in the multivariate linear re- gression after adjusting others variable (t= -3.23, p=0.001). The result is in line with that of other studies demonstrating the relationship between work experience and PTSD (27, 28). Furthermore, a positive correlation was reported between the number of missions and the total PCL-5 score ( β= 0.07) based on the multivariate linear regression after adjusting the variables. The result may reflect the effect of more expo- sure to traumatic events on PTSD. In another study in South Africa, the same relationship was observed between expo- sure to traumatic incidents and prevalence of mental health problems among emergency medical care personnel (29). In addition, the results are in line with some other studies in which it was reported that ongoing exposure and gaining enough experience simultaneously can increase the techni- cian’s ability to adapt, and develop resilience to stress over traumatic events (30, 31). The history of previous training and psychological debrief- ing sessions on managing and controlling stress in the pre- hospital emergency was regarded as another factor which was evaluated in the present study. Among the 259 partici- pants, almost 54% had previous training. However, no sig- nificant relationship was reported between previous train- ing and the total PCL-5 score (t= -0.83, P=0.319). The re- sults of other studies indicated a considerable difference in the effect of training on reducing the stress among staff. For example, some studies emphasized that regular counseling or defusing sessions, as well as psychological debriefing and Critical Incident Stress Management (CISM), which is con- sidered as an adaptive and short-term psychological helping- process, can prevent PTSD symptoms in personnel (32, 33). However, the results of a systematic review study showed that psychological debriefing has no preemptive effect on the PTSD incidence while Cognitive Behavior Therapy (CBT) for four weeks or more may prevent the development of trauma- related psychological disorders (34). The level of education was another factor whose possible ef- fect on the total PCL-5 score was evaluated (p=0.935) because the personnel’s job in the EMS of Iran may not be related to the capability, skills, and training they have acquired. All- Advanced Life Support (ALS) and Basic Life Support (BLS) are performed by technicians with the same title (EMT), skill, and job responsibilities, which result in varying stress reac- tions. However, EMTs are divided into several levels in terms of training and clinical skills they have acquired such as EMT- B (Basic), EMT-I (Intermediate), and AEMT (Advanced) (35). For example, Minnie et al. reported that EMTs with a BLS and ILS qualification find all prehospital emergencies more trau- matizing than those with an ALS qualification, and the dif- ference observed was considerable for road traffic incidents (36). Therefore, in these countries, EMTs are dispatched to basic and advance emergencies in accordance with their This open-access article distributed under the terms of the Creative Commons Attribution NonCommercial 3.0 License (CC BY-NC 3.0). Downloaded from: http://journals.sbmu.ac.ir/aaem 5 Archives of Academic Emergency Medicine. 2021; 9(1): e35 skills and abilities, which makes the technicians more adapt- able in the face of traumatic events, and accordingly they ex- perience less stress than the other EMTs. Finally, the results of the present study suggest that EMS au- thorities should be aware of some modifiable risk factors re- lated to PTSD in order to adopt a proper follow-up and take preventive measures for EMTs at risk. Therefore, conducting a qualitative study to uncover poten- tial stresses in exposure to the variety of prehospital emer- gency bases is essential. In addition, it is possible to reduce PTSD incidence in EMTs by changing some factors such as reducing the number of shifts, as well as increasing the staff’s experience by exposing them to traumatic events in a simu- lated environment. 5. Limitations The results of the present study may not be generalizable to other contexts. In the present study individuals who had previously been diagnosed with PTSD or recovered were ex- cluded, which could lead to an underestimation or overesti- mation of PTSD rate in the present study. Also, the findings may be gender biased due because of the lack of female tech- nicians in the pre-hospital system considered as sample in the present study. No study has focused on determining the proper cut-off point for the PCL-5 instrument in the EMS staff in an Iranian context. Hence, the cut-off point used to determine PTSD in the present study may not give an accurate prediction of the participants at risk. Variation in estimating the levels of PTSD can be related to the use of different PTSD assessment tools in the prehospital emergency (22). Few studies have been conducted using the PCL-5 tool for examining and detecting PTSD among EMTs. Therefore, comparing the results of the present study with other studies may produce some type of bias (39). 6. Conclusion The results indicated that the prevalence of PTSD among EMT personnel of hamadan province is high. Negative alter- ations in cognition and avoidance were the most and least common clusters, respectively. EMTs with the age of ≤ 30 years, work experience of ≤ 10 years, married status, informal employment, emergency medical technician’s degree, and more than 8 shifts per month, as well as no previous train- ing history had a higher total PCL-5 score. 7. Declarations 7.1. Conflict of interest The authors report no conflict of interest and are responsible for the content and writing of the paper. 7.2. Acknowledgments Abbas Mogimbeigi analyzed the data and aided in interpret- ing the results of the present study. Therefore, we would like to thank his for leading to better quality of results. 7.3. Funding and support The present project is a part of a PhD dissertation sup- ported by Tehran University of Medical Sciences (grant No: 9421199001). 7.4. 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McGauran N, Wieseler B, Kreis J, Schüler Y-B, Kölsch H, Kaiser T. Reporting bias in medical research - a narrative review. Trials. 2010;11:37-. This open-access article distributed under the terms of the Creative Commons Attribution NonCommercial 3.0 License (CC BY-NC 3.0). Downloaded from: http://journals.sbmu.ac.ir/aaem A. Khazaei and et al. 8 Table 1: Relationship between the mean total PCL-5 score of each cluster with having or not having post-traumatic stress disorder (PTSD) PCL-5 Clusters Total PTSD P* No (n = 207) Yes (n = 52) Intrusion 4.98 (3.08) 4.06 (2.48) 8.67 (2.40) < 0.001 Avoidance 2.25 (1.70) 1.85 (1.42) 3.85 (3.62) P<0.001 Negative alterations in cognitions 7.42 (4.63) 5.85 (3.40) 13.67 (3.47) P<0.001 Alterations in arousal and reactivity 6.91 (4.15) 5.68 (3.44) 11.83 (2.92) P<0.001 *: Mann-Whitney test. Data are presented as mean (Standard deviation). Table 2: Relationship between the personal/work-related characteristics with the total PCL-5 score as well as the mean PCL-5 scores of each cluster Characteristics n (%) The Mean (SD) PCL-5 Cluster Scores Total P Value Intrusion Avoidance Cognition Arousal Age (years) ≤ 30 92 (35.5) 6.61( 3.26) 2.88 (1.78) 8.92 (5.43) 8.61 (4.49) 27.02 (12.70) 31-40 134 (51.7) 3.73 (2.59) 1.77 (1.49) 6.02 (3.91) 5.50 (3.67) 17.08 (9.42) < 0.001 > 40 33 (12.7) 5.55 (2.03) 2.45 (1.67) 8.91 (2.93) 7.91 (2.81) 24.82 (7.00) Work experience (years) ≤ 10 166 (64.1) 5.47 (3.36) 2.42 (1.75) 7.90 (5.13) 7.49 (4.43) 23.31 (12.45) 11-20 89 (34.4) 4.20 (2.92) 2.02 (1.55) 6.69 (3.44) 5.98 (3.41) 18.91 (8.62) 0.204 > 20 4 (1.5) 2.25 (0.5) 0.25 (0.5) 4.00 (2.44) 3.75 (2.06) 10.25 (4.39) Marital status Single 83 (32) 4.78 (3.03) 2.18 (1.75) 7.27 (4.52) 6.74 (4.21) 21.02 (11.73) Maried 171 (66) 5.43 (3.23) 2.40 (1.61) 7.65 (4.89) 7.33 (4.12) 22.81 (11.09) < 0.001 Divorced 5 (1.9) 4.60 (1.14) 2.20 (1.70) 8.80 (4.63) 5.80 (4.15) 21.40 (6.34) Employment status Formal 97 (37.5) 4.43 (2.25) 2.11 (1.63) 7.09 (3.45) 6.49 (3.60) 20.15 (8.86) 0.282 Unformal 162 (62.5) 5.31 (3.45) 2.33 (1.74) 7.62 (5.21) 7.16 (4.43) 22.46 (12.70) Degree EMT 130 (50.2) 5.29 (3.50) 2.50 (1.88) 7.57 (5.03) 6.79 (4.30) 22.20 (12.51) Nurse 61 (23.6) 5.11 (3.05) 2.09 (1.65) 7.57 (5.00) 6.86 (4.42) 21.63 (12.68) 0.935 Operation 35 (13.5) 4.09 (2.66) 1.97 (1.48) 7.39 (4.01) 6.79 (3.75) 20.30 (9.91) Anastesia 33 (12.7) 4.74 (2.16) 1.97 (1.32) 7.03 (3.85) 7.26 (3.94) 21.00 (9.02) Base location Urban 165 (63.7) 5.17 (3.13) 2.35 (1.76) 7.59 (4.74) 7.23 (4.09) 22.38 (11.22) Road 69 (26.6) 4.87 (3.00) 2.14 (1.61) 7.48 (4.75) 6.64 (4.49) 21.13 (12.42) 0.146 Air 25 (9.7) 4.08 (3.05) 1.92 (1.52) 6.16 (3.42) 5.56 (3.40) 17.72 (9.54) Number of shift (per month) ≤ 8 20 (7.7) 1.80 (1.60) 0.65 (0.98) 2.00 (0.00) 1.80 (0.61) 6.45 (2.11) < 0.001 > 8 239 (92.3) 5.25 (3.03) 2.38 (1.68) 7.78 (4.51) 7.34 (4.03) 22.78 (10.99) Number of missions (in the last month) ≤ 80 109 (39.4) 4.71 (3.00) 2.08 (1.52) 7.01 (4.23) 6.43 (4.16) 20.23 (11.34) 0.098 > 80 157 (60.6) 5.17 (3.13) 2.36 (1.80) 7.69 (4.87) 7.22 (4.12) 22.49 (11.47) Previous training Yes 139 (53.7) 4.76 (3.00) 2.39 (1.69) 7.37 (4.68) 6.53 (3.93) 21.01 (11.25) 0.375 No 120 (46.3) 5.25 (3.17) 2.09 (1.70) 7.48 (4.60) 7.35 (4.36) 22.24 (11.69) SD: standard deviation. This open-access article distributed under the terms of the Creative Commons Attribution NonCommercial 3.0 License (CC BY-NC 3.0). Downloaded from: http://journals.sbmu.ac.ir/aaem Introduction Methods Results Discussion Limitations Conclusion Declarations References