A longitudinal study on stress sources perceived by Chilean dental students

Materials and methods: Exploratory, non-experimental, longitudinal descriptive study. The Spanish version of the Dental Environment Stressors (DES) questionnaire was applied, adapted and validated for the dental students of the San Sebastián University (Concepción, Chile) in May and October 2016. The sample consisted of 83 first-year students evaluated. A general comparison of the variables under study (stress and its dimensions) was made for both periods, considering genders and using the Student’s t-test. Fisher’s F test was used after estimating whether or not there was equality of variances between the groups.


Introduction
The literature defines stress as the relationship between an individual and the environment; therefore, it is a psychosocial factor, in which some of its characteristics are perceived as a threat to physical or mental health.(1)(2) Stress can lead to permanent tiredness, headaches, digestion problems, drowsiness, and sleep and mental health disorders.(3)(4)(5) Compared to students from other health programs, dental students seem to be affected by stress in a higher proportion.(6)(7)(8)(9) Around 90% of the students have reported high stress rates when they feel overworked in short periods of time.In consequence, an intervention in this regard would help reducing such rates.(10)(11) Most universities do not have instruments to perform an initial evaluation of their students, so many personal characteristics and psychosocial factors that could be determinant in the development of pathologies associated with stress are still unknown.Additionally, stressors related to academic stress have only been evaluated at certain moments, and their evolution has been rarely studied during the course of the academic year.(12)(13) The perception of university students regarding academic stress is highly relevant to obtain valuable feedback on the efficiency and acceptability of educational methods.The stressful nature of Dentistry can be experienced since the beginning of training, when students are expected to acquire a wide range of knowledge and skills that will help them succeed in their studies and their profession.(1,5) Different works show a higher prevalence of stress and emotional disturbances in medical and dental students in whom psychological disorders, including depression, anxiety and stress, are more frequently documented worldwide compared to other health careers.(3,6,8,(14)(15)(16)(17) In addition, the psychological health condition of these students becomes evident in terms of low academic achievement levels and satisfaction with life.(18,19) In this scenario, stress represents a major challenge, especially during the first year of studies, considering the lack of a learning strategy, sleepless nights and inadequate eating during exams.(20) There is evidence of different stressors perceived by first-year dental students, understanding perception as an idea or knowledge of something through the senses.(8,21) However, to date, research on perceived stress among groups of Spanish-speaking students is scarce and only a handful of studies evaluate the perception of stress in first-year students during the first and second semesters.Therefore, the role that stress may have on students at the beginning of their professional studies has not been considered.(13) Many of the studies that provide information regarding the correlation between stressors and academic year do not present clear data in relation to gender.(22)(23)(24)(25) While most of them report higher stress rates in female dental students (22,25), one study reported higher levels in men (26) and one reported no overall differences between genders.(27) For this reason, the objective of this research is to evaluate the differences in stress factors perceived by first-year dental students during the first and second semesters according to gender, in order to promote the adoption of preventive measures and minimize the negative effects of stress on these students.

Materials and methods
This was an exploratory, non-experimental, longitudinal descriptive study.The cohort was made up of all first-year undergraduate dental students from the San Sebastián University (SSU) in Concepción-Chile, officially enrolled in 2016.Participation in the study was voluntary, the confidentiality of the students was maintained and the ethical principles of the Helsinki Declaration were followed.
The sample was selected for convenience based on the following exclusion criteria: students absent on the day of application of the questionnaire, and those who did not wish to participate in the study or did not sign the informed consent.The Dental Environment Stressors (DES) DES30-Sp survey was applied twice during the academic yearthe first week of May and October 2016-, corresponding to the third month of the first and second semesters, using a pencil.The month of May was selected since, at this point, the students have already experienced at least two months of immersion in a university educational environment and have acquired an idea or knowledge about the future of their university career, and October because it coincides with other studies that have applied the DES questionnaire.(13) Factors such as class size, leisure time, assessment procedures, peer and teacher relationships, ethical climate, extracurricular opportunities, beliefs, attitudes and sociocultural background influence significantly the way how students perceive and experience their education.(12,22,28) However, the Garbee's Dental Environment Stressors questionnaire -modified by Westerman (26) and Polychronopoulou (29)-has been widely used in research studies.(3,8,12,(30)(31) Polychronopoulou & Divaris (29) reviewed the instrument, presenting a 30-item version that was later used in multinational and longitudinal studies among dental students.(23,31) The DES30-Sp in Spanish is an instrument validated by Fonseca et al. (13) in Chile.It includes 30 items regarding stressful dental educational environments that students must classify based on a scale considering their potential as stress generators.In this way, a score of 1 is assigned to a factor that is not stressful at all; 2, for somewhat stressful; 3, for quite stressful, and 4, for very stressful.This instrument includes stressors such as "qualifications and exams", "lack of time for relaxation", "patients arrived late or did not make an appointment", "lack of confidence to be a successful student" and "ddifficulty of the work assigned in classes", among others.Its psychometric properties are good (Cronbach's alpha =0.89), it is easy to use and its application time is approximately 15 to 20 minutes.( 13) Gender (male /female) and the academic semester when the survey was applied (first/second) were the independent variables, while the total score was the dependent variable.Scores of 2 and higher suggest the presence of high stress levels.
The Kolmogorov-Smirnov test (K-S test) was used for the statistical analysis of the data on the averages of stress levels during the different collection dates and on gender.(32) The internal reliability of the data was estimated using the general Cronbach's alpha and the resulting values as each of the elements (questions); intraclass correlation coefficient, Hotelling's T2, and Tukey's nonadditive test were eliminated.
Subsequently, mean, standard deviation and standard error of the mean for both periods and genders were estimated for general stress and for each of its dimensions.The comparison of the variables under study (stress and its dimensions) for both periods, in general and considering genders, was performed using the student's t-test, after estimating whether or not there was equality in the variances between both groups using the Fisher's exact test (F-test).If the F-test was significant, the student's t-test was used (t prime); if it was not significant, the student's t-test was used in agreement with Díaz-Narváez.(33,34) The level of significance was α≤0.05.

Results
The sample consisted of 83 students.Cronbach's alpha was satisfactory (untyped and typified =0.932), thus leading to infer that the data had internal reliability.The total Cronbach's alpha value, if an element (question) was removed, ranged between 0.928 and 0.933, which demonstrated the reliability of the test regardless of the presence of any of the elements.The intraclass correlation coefficient was 0.932 (F=14.7,p=0.001), which confirms the good reliability of the data.Hotelling's T2 test (F=19.7,p=0.001) and Tukey's nonadditive (F=6.17,p=0.01) allow, in the first case, to infer that the means of the questions are different from each other, which shows that not all contribute equally to the global mean (X=2.56), and also the variability between the responses of the instrument.In the second case, it is possible to infer that there is an additive character in the data, which suggests the need of a bigger sample for future research.
Table 1 presents the results of the comparison between stress perception and its dimensions in both periods examined.Perception of stress in general was not significant; however, when examining the "Clinical Training" dimension, it was highly significant.The negative sign of the statistical test indicates that the values of this dimension are greater in the second measurement than in the first.
Table 2 presents the same comparison but considering the female gender exclusively.The results show that the only significant comparison was "Clinical Training".The negative sign of the statistical test shows that the values of this dimension are greater in the second measurement in relation to the first; these results consider exclusively the male gender and do not show any significant differences in perception of stress in general and in each of its dimensions (table 3).

Discussion
Stress varies from person to person and occurs when the pressures and demands they face, whether real or imagined, are perceived as excessive.( 16) Despite the lack of cut-off scores, scores of 2 and higher suggest the presence of high stress levels in the general analysis of DES.(8) In consequence, the results of this study show moderate initial stress levels, which coincides with Silverstein & Silverstein in the U.S (24), who also found an initial level of stress in dental students that might be related to moving away from their usual social circle, developing new friendships, immersing themselves in a new environment, presenting own insecurities, financial concerns or academic performance.(35)(36)(37) The results of the DES questionnaire, regarding the different dimensions, could shed some light on what students consider a cause of stress in the Faculty.With this in mind, the predominant stressors found in this research in descending order and considering the absolute mean values are "Academic workload", "Academic performance", "Patient treatment" and "Self-efficacy beliefs".These results differ from Silverstein & Silverstein, since they determined that the financial responsibility, stressor belonging to the item "Others", is the most predominant, followed by "Academic performance" and "Academic Workload".(24) This difference could occur, in part, because in Chile the financial burden falls on the family and not directly on the student.
The changes experienced by the students, who go from high school to the university, becomes relevant because they are subject to a greater academic load, which may lead them to think that they will not be successful and will fail, causing stress and anxiety.(37)(38) The third predominant factor is "Patient treatment", which is surprising because students do not interact with clinical subjects or patients in the first year.This may reflect the effect of the academic environment on second-semester students, who may be transferring their negative impressions to freshmen.On the other hand, a statistically significant difference was observed in the "Others" dimension between the mean of the data of May and October.This dimension includes extracurricular factors related to personal, socioeconomic and future employment situation, and could be explained, in part, by the uncertainty generated by events such as changing city, which leads us to think of adaptation to these factors by the new students.(24) When analyzing the stress level perceived per semester, it is evident that, at the beginning of the second semester, perception increases compared to the first semester.This coincides with other longitudinal studies made in Jordan, Greece and the U.S, which obtained a similar result (3,8,(23)(24), and with several transversal studies made in Turkey, Chile and Malaysia that indicate high stress levels.(7,13,30) All of this shows that Dentistry is a highly demanding career and can lead to emotional, psychological or physical difficulties for students.
On the other hand, the predominant factors of the second semester, considering the absolute values of the means in decreasing order, are "Academic Performance", "Academic Workload", "Patient treatment" and "Self-efficacy beliefs".This means that a high perception of the same factors of the first semester is maintained, but this time, "Academic Performance" ranks first in terms of absolute values.These results agree with several studies conducted in Chile, Jordan, Malaysia and Nepal (1,3,8,30,39), where the DES instrument was also applied.In this context, the work of Fonseca et al. is relevant since it was applied in Chile and Argentina obtaining similar results.(13) Polychronopoulou & Divaris (23) also point out "Patient treatment" as a stress factor in the first year, which is striking considering that "Clinical training" had a statistically significant result when compared to the first semester.It is important to highlight this result as several studies have modified the DES by eliminating factors related to patients and the clinic to adapt it to students of pre-clinical courses.(3,8,22,(24)(25) Moreover, the results show that clinical training is higher in women.This could be explained since women reportedly have greater interpersonal skills as well as a greater perception and understanding of emotions, while men stand out for greater ability to control impulses, tolerance to stress and greater ability to repair their emotional states.(40)(41) This greater tendency of women to attend their emotions, together with the smaller capacity of repair, could explain the higher scores obtained for this dimension.There is evidence that certain areas of the brain dedicated to emotional processing may be larger in women than in men.Another study indicates that brain activity is different according to gender.(40) Many research studies suggest that differences in intensity of response to perceived stressors could be explained by the various patterns of psychological morbidity and the social construction of masculinity in which men tend not to express their concerns.(1,23,30,42,43) In addition, Sanders & Lushington explain that this could occur due to different patterns of response to stressful events by sex.(44) Research conducted in India by Shashidhar (45) and Kumar et al. (46) showed that men presented higher levels of stress than women did.Other studies, conducted in Australia and Europe did not find gender differences.(31,44) This may indicate a cultural difference in gender-related stress response, which may not be associated with the perception of stress but rather with sociocultural influences.(25) The results obtained here show that students have a certain perception before actually interacting with the patients and the clinic.Therefore, this factor should be considered in future studies of stress in students, even at the pre-clinical stage.It is important to consider these factors to implement stress management measures from the very beginning of the career, and to develop cohort studies to learn about the evolution of these students in the following academic years.This is relevant since evidence shows that dentists are more prone to occupational exhaustion or burnout, anxiety and depression due to the multiple sources of stress in their academic and professional life (25,47,48), which leads to a higher risk of developing problems such as insomnia, headache, cardiovascular and gastrointestinal diseases, back pain, chronic fatigue, among others.(49,50) In conclusion, this research shows that stress related to patient care begins at early stages of the professional career -first year -, so measures must be planned and implemented from the beginning of the career.
The limitations of the study include the fact that only first-year dental students of one academic program participated, thus limiting the size of the sample, and the fact that the study was a follow-up to the course group and not the student.

Conclusion
Stress was perceived in all items of the DES questionnaire, where women had a higher score in the dimension "Clinical training".Further studies should include a larger sample, with individual follow-up.It is worth noting that the clinical field is important for first-year students, therefore, it is necessary to take steps to improve the academic environment during the course of the academic program.

Table 1 .
Results of the comparison of stress perception and its dimensions in both periods in dental students from the San Sebastián University in Concepción (Chile), 2016.
X: arithmetic mean of stress in general and of each component at different periods; σ: standard deviation; ns: not significant.* highly significant.Source: Own elaboration based on the data obtained in the study.

Table 2 .
Results of the comparison of stress perception and its dimensions in both periods in female dental students from San Sebastián University in Concepción (Chile), 2016.
X: arithmetic mean of stress in general and of each component at different periods; σ: standard deviation; ns: not significant.* Significant 5%.Source: Own elaboration based on the data obtained in the study.

Table 3 .
Results of the comparison of stress perception and its dimensions in both periods in male dental students from San Sebastián University in Concepción (Chile), 2016.
X: arithmetic mean of stress in general and of each component at different periods; σ: standard deviation; ns: not significant.Source: Own elaboration based on the data obtained in the study.