Psychometric Properties of the Croatian Language Version of the Dental Environment Stress Questionnaire on Dental Medicine Students.

OBJECTIVE: To develop the Croatian version of the 41-item Dental Environment Stress questionnaire (DES) for stress assessment of dental students in both, preclinical and clinical years of study and to test its psychometric properties in Croatian dental student population.
MATERIALS AND METHODS: The English version of the 41-Item DES questionnaire was first translated into the Croatian language. Subsequently, it was set on the google drive and filled out by a total of 202 students from the School of Dental Medicine, University of Zagreb and 30 additional students from other Faculties. Students also assessed their overall level of stress on the Likert scale (1=no stress, 5=highest level of stress). Internal consistency was tested on 202 dental students; test-retest reliability on 30 dental students who filled out the same questionnaire twice; convergent validity on 202 dental students; and divergent validity on 202 dental students and 30 students from faculties not belonging to the biomedicine group.
RESULTS: Internal consistency showed high Cronbach alpha coefficient (0.9) and test-retest reliability showed no significant difference (P>0.05) within the period of 14 days when stress level had not changed (vacation). Convergent validity was confirmed by the significant association between the DES summary scores and the self- perceived level of stress (Spearman's rho=0.881; P<0.001). Divergent validity was confirmed by significantly lower DES summary scores in students not belonging to the Biomedicine group (t=7.5, P<0.001).
CONCLUSION: Excellent psychometric properties of the Croatian version of the DES questionnaire enable its utilization for assessment of stress level in Croatian dental students.

Introduction

It has been proved that academic stress negatively affects students’ performance (). Many reports indicate that students of medicine, dentistry, and pharmacy (biomedicine study groups) experience high levels of stress during the course of their studies (-). Psychological stress occurs when an individual perceives that environmental demands exceed his/her adaptive capacity, resulting in psychological and biological changes that may place the individual at risk for a disease (). Prolonged distress may lead to a wide range of negative outcomes, such as reduced academic performance, unprofessional conduct, burnout, etc. ()

Psychological stress among dental students has been a subject of interest for numerous investigators from all around the world (–) in order to find coping strategies (). However, to conduct a reliable research one must have an adequate instrument. It is, therefore, necessary either to create a new instrument to measure a level of stress in dental students or to translate and adapt the already existing instrument. In the available dental literature, stress levels in dental students have been measured using various questionnaires, such as General Health Questionnaire (GHQ-12) which was used to assess psychological stress of students () or the Perceived Stress Scale (PSS) () and the Depression Anxiety and Stress Scale (DASS) (). The most frequently used questionnaire in multicentric studies was the 38-item Dental Environment Stress Questionnaire (DES) (, , -). It evaluated stress sources in dental students with answers to the four-degree Likert scale. The 38-item DES questionnaire has been recommended only for the senior years of study, which involve a clinical work. The shortened 26-item version of the DES questionnaire without questions related to clinical work has been described in the dental literature for students of the first and the second year (preclinical years) (). One more version of the DES Questionnaire has been developed to fit both, the higher and the lower years of study. It comprises 41 questions (25 original questions from the DES questionnaire and 16 revised questions) divided into seven categories (dimensions) related to various potential sources of stress in dental students: Assessment of own effectiveness, Faculty and Administration, Workload, Patient Therapy, Clinical Training, Pressure due to Proper Tasks, and Social Stressors. In the 41-item DES questionnaire dental students evaluate amount of stress on the Likert scale of 4 degrees (0 = no stress or question cannot be applied; 1 = low stress, 2= medium stress, 3 = highest stress) (, ).

Aim of the study

The aim of the study was to develop the Croatian version of the 41-item DES questionnaire, which measures stress in dental students in both, preclinical and clinical years of study. The aim was also to test its psychometric properties in Croatian dental student population.

Hypothesis of the study

The hypothesis of this study was that the existing DES questionnaire, which measures stress levels in dental students and had already been adapted in many other countries will showed good psychometric properties in the cultural environment of the Croatian population and that it could be used for assessment of stress level in Croatian dental students.

Patients and Methods

Participants

The study was approved by the institutional Ethics Committee. A total of 202 students from the School of Dental Medicine, University of Zagreb were included, as well as additional 30 students from other Faculties of the University of Zagreb, not belonging to the biomedicine group of studies. Students from the School of Dental Medicine, University of Zagreb received a written request via Facebook profile of their respective year of study, together with a brief explanation about the aim of the study and instructions how to fill out the DES questionnaire using the 4-degree Likert scale (0 = no stress or question cannot be applied; 3 = highest stress). The 41-item DES questionnaire was set on the Google Drive; therefore any student who wanted to participate could easily reach the questionnaire and fill it out on-line. A total of 30 male students (14.9%) and 172 female students (85.1%) from the School of Dental Medicine participated in the study. There were 31 students (15.3%) belonging to the first year of study, 27 students (13.4%) belonging to the second year, 41 students (20.3%) belonging to the third year, 30 students (14.9%) belonging to the fourth year, 45 students (22.3%) belonging to the fifth year of study, and 28 students (13.9%) belonging to the sixth year of study. Additional 30 students from other faculties (not the Biomedicine group) filled out a printed version of the DES questionnaire.

Instrument

The modified DES questionnaire, i.e. the 41-item version which can be used for both, preclinical and clinical students was chosen and translated from the English language into the Croatian language according to the accepted standards (). In each of the 41 questions, the subjects were asked to describe their self-perceived level of stress. Their responses were rated on the 4-degree Likert-type scale (0 = no stress or question cannot be applied; 1 = low stress, 2 = medium stress, 3 = very high level of stress). In addition to completing the questionnaire, the respondents were also asked to grade their overall self-perceived stress level due to dental environment on the 5-point Likert scale from 0 to 4 (0 = no stress, 4= the highest possible level of stress).

The translation from the English language version was done jointly by a professional translator familiar with dental vocabulary and a dentist with excellent knowledge of the English language. The translation was reviewed by two Croatian (Department of Prosthodontic, School of Dental Medicine, University of Zagreb, Croatia) dentists and one dental student, with excellent knowledge of English. The translators and language reviewers worked independently. The final version of the DES questionnaire was back-translated into English jointly by another professional translator and one dentist and student with an excellent knowledge of English. The back-translation was evaluated by one native speaker of English who compared the back translation with the original English version. Prior to the back-translation, a pilot study was conducted in a group of 15 students to test the clarity of the questions. Afterwards the psychometric properties were tested: validity and reliability.

Psychometric properties of the 41-item DES questionnaire

Validity

Convergent validity was determined from the association between self-reported level of stress and the 41-item DES summary score by using the Spearman rank correlation. Discriminant validity was determined by comparison of the 41-item DES questionnaire summary scores obtained from the students of the School of Dental Medicine University of Zagreb and from 30 students not belonging to the Biomedicine group of studies (students from the Faculty of Humanities and Social Science, Faculty of Electrical Engineering and Computing, Faculty of Law, Faculty of Mechanical Engineering and Naval Architecture).

Reliability

Two types of reliability were assessed – the test-retest reliability and the internal consistency. To assess the test-retest reliability, the 41- Item DES questionnaire was administered twice within a two-week time-interval during student vacations (we assumed there will be no fluctuation in the level of stress during vacation) in 30 dental students (8 men, 22 women). It was predicted that the DES summary score would not change during the two-week period because there could not be any fluctuations in the level of stress elicited by dental surroundings due to the vacation period.

The internal consistency was assessed by calculating the Cronbach reliability coefficient α.

Statistical analysis

Statistical analysis was performed using Statistical Package for the Social Sciences, version 20.0 for Windows (SPSS Inc., Chicago, IL, USA) and Microsoft Office Excel 2003 (Microsoft, Seattle, WA, USA).

Results

Validity

Convergent validity

The test was performed on a total of 202 dental students who filled out the DES questionnaire. Apart from filling out the DES Questionnaire, they also assessed their level of stress which they perceived due to the influence of dental environment during the study. They assessed their overall level of stress due to dental environment by using the 1-5 Likert scale with answers: 1=no stress; 5= the highest level of stress. Convergent validity was verified by a highly significant association (Spearman’s rho=0.881; P<0.001) between the DES Summary score and the self- assessment of the level of stress perceived due to dental environment.

Divergent validity

To test the divergent validity of the 41-Item DES questionnaire, the summary scores were compared between students from the School of Dental Medicine, University of Zagreb and students from other faculties (University of Zagreb) not belonging to the Biomedicine group (Faculty of Humanities and Social Science, Faculty of Electrical Engineering and Computing, Faculty of Law, Faculty of Mechanical Engineering and Naval Architecture). The t-test for independent samples was performed. It was assumed that students from other faculties would have a lower level of stress caused by dental environment than dental students. The mean values of the DES summary scores and standard deviations for dental students and for students of other faculties are presented in Figure 1. As predicted, there was a significant difference between the two groups of students (t = 7.57, df = 230, P< 0.001) with significantly higher scores (higher stress) obtained from dental students.

Figure 1

Mean values and standard deviations (bars) of the Croatian version of the 41-Item DES questionnaire summary scores between students of the School of Dental Medicine and students from other faculties not belonging to the Biomedicine group of studies (t = 7.5; df= 230; P < 0.001)

Reliability

The internal consistency

The internal consistency was assessed by calculating the Cronbach coefficient α. The Cronbach alpha coefficient for both, the 41-Item DES questionnaire, and for the DES questionnaire when an item was deleted from 202 dental students were more than satistactory (Cronbach's alpha = 0,90 and Cronbach's Alpha if Item deleted = 0.89-0.93).

The test-retest reliability

The test-retest reliability was evaluated in 30 dental students (8 males and 22 females) during the vacation period, when no changes in the level of stress were predicted (Figure 2). Students filled out the 41-Item questionnaire twice (at baseline and after the period of two weeks). There were no significant differences between the two completions of the same questionnaire, as predicted (t = -0.844, df = 29, P = 0.405; > 0.05; NS).

Figure 2

Mean values and standard deviations of the Croatian version of the 41-Item DES questionnaire summary scores obtained from 30 dental students during their vacations (t = -0.844, df = 29, P = 0.405; NS)

Discussion

The Croatian version of the 41-Item DES questionnaire showed very good psychometric properties. The 41 items of the DES questionnaire have been clustered into seven domains of potential stressors: self-efficacy beliefs (items 1–9), faculty and administration (items 10–19), workload (items 20–25), patient treatment (items 26 to 29), clinical training (items 30–33), performance pressure (items 34–36) and social stressors (items 37–41). However, the above-mentioned categories were not shown in the questionnaire, hence the students were not aware of them during filling out the questionnaire. The number of female students was significantly higher than that of male students throughout all study years, from the first to the last year, which can be easily explained by the fact that students of the School of Dental Medicine, University of Zagreb are predominantly females: about 80% female students.

In Croatia, no instrument has existed to measure influence of different stressors during study of dental medicine. Therefore, to perform a research and find out the level of stress in Croatian dental students we could develop a new instrument or adapt the existing one (-). The development of a new instrument would not allow any comparison with dental students in other countries. Hence, it seemed reasonable to adapt the existing instrument, which had already been adapted in many other countries. Therefore, we decided to adapt the 41-Item DES questionnaire which measures stress levels in both, preclinical and clinical students (). After the translation and a pilot study which proved a good understanding of questions, psychometric properties of the instrument were investigated.

The Cronbach α is a summary statistics, which captures the extent of agreement between all possible subsets of questions. The Cronbach α values >0.80 indicate a reliable scale, although at the initial stages of the study, values >0.70 are also acceptable (). This study showed satisfactory values for the Cronbach α coefficient. Test-retest also showed no significant differences between the two completions of the DES questionnaire during the 14 day vacation period.

Convergent validity measures constructs that, theoretically, should be related to each other. Adequate convergent validity in this study was shown by a significant association between the DES summary score and the self-perceived level of stress.

Divergent validity measures constructs that, theoretically, should not be related to each other and this was proved for the DES questionnaire by significantly lower DES summary scores in students not studying dental medicine compared to dental medicine students.

Due to its good psychometric properties, the DES questionnaire can be implemented in the Croatian dental academic community in order to find out stressors and to cope with them (, ).

It should be noted that this study has some limitation, which include relatively a small number of students on each year who completed the DES questionnaire (about 25 percent of students). It is presumed that students were probably to busy by learning and other responsibilities at the faculty as well as outside the faculty.

Conclusion

In conclusion, this study confirmed the fact that the 41-Item DES questionnaire is a suitable instrument for the assessment of stress level in dental students and can be used in longitudinal, cross-sectional, and cross-cultural studies.