Study design
Our cross-sectional study was carried out between August 2010 and August 2012 at 13 special schools focusing on motoric and/or holistic development of severely and multiple handicapped children in Rhineland-Palatinate (Germany). The main objective of the study was to survey data on physical and psychological strains and several health outcomes of teachers and educational staff at this type of school. Between August and September 2010, an information letter with a brief description of the course of the study was sent to the head teachers of all 15 schools focusing on motoric and/or holistic development of severely and multiple handicapped children in Rhineland-Palatinate. Altogether, 13 schools comprising 245 teachers and 417 educational staff were interested in participating. The head teachers of the two schools which did not participate asked the principal investigators to participate at a later time when the study was already completed. Subsequently the project was presented to the employees of the interested schools at teachers´ councils between October and December 2010. Directly following the presentation, an information letter about the whole project along with a written informed consent form was deposited in the personal “letter boxes” of all teachers and educational staff at the interested schools. The informed consent form has been signed by all participants. The individual registration deadline for a participation in the study was four weeks after the teacher´s council.
All participating schools received a detailed plan of action, including dates of interviews. In order to minimize any disturbances of regular teaching activities, the participants were allowed to determine the date of participation. The study was carried out directly at the schools. Data were surveyed using written questionnaires.
The study was conducted by the Institute of Occupational, Social and Environmental Medicine and the Institute for Teachers´ Health at the University Medical Center of the Johannes Gutenberg University of Mainz.
The study was approved by the State Ministry of Rhineland-Palatinate for Education, Science, Further Education and Culture (MBWWK), the supervision and service administration body (ADD) in Trier, the main staff councils of the special schools for children with learning difficulties, the ethical committee of the medical association of the German State of Rhineland-Palatinate, and the responsible principals and the local staff councils.
Questionnaire
The data for the present article were surveyed using a medical history questionnaire, containing 84 questions covering the topics basic sociodemographic information, professional qualification/requirements, personal state of health, musculoskeletal strains and disorders, prevention and risk of infections/vaccination status, psychological health, work-related accidents, and health-related behavior. The majority of the questions included in the medical history questionnaire were developed by the Institute of Occupational, Social and Environmental Medicine. In addition, 21 questions were adopted from the questionnaire of the GEDA (Ge sundheit in D eutschland a ktuell) study [10–12]. The latter study was commissioned by the German Federal Ministry of Health and carried out by the Robert Koch-Institute.
Variable construction
The dependent variable “chronic back pain” was surveyed by the following two questions adopted from the GEDA-questionnaire:
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Have you ever had (almost) daily back pain for three months or longer? (Yes, No, I don´t know)
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If yes, has this also been the case in the last 12 months? (Yes, No, I don´t know)
If the respondents agreed to both questions, they were categorized as having had chronic back pain in the last 12 months. If one of the questions was answered with “No” or “I don´t know” they were coded as not having suffered from chronic back pain during the aforementioned period.
Regarding sociodemographic variables, information on age, sex, marital status, highest level of education, and profession was used. Age was defined as the present age (in years) when completing the questionnaire. Information on the educational background of the respondents was obtained by asking for the highest level of education, using the categories “Abitur”, “Fachhochschulreife/Fachoberschule”, and “Mittlere Reife”. Generally speaking, German school-leaving qualifications do not have exact counterparts in most other countries. While the “Abitur” takes 12 to 13 years of school and is the entry qualification for the universities, “Fachhochschulreife/Oberschulreife” takes 12 years of school and permits entering an advanced technical college, whereas “Mittlere Reife” is obtained after 10 years of school without being able to study at a university or college. The profession of the respondents was obtained by asking whether they were actually working as teachers or as educational staff. The term “educational staff” is not clearly defined and is rather a collective name for all non-teachers working at special schools (e.g. physiotherapists, ergotherapists, nursery school teachers, remedial teachers, social education workers, speech therapists, etc.). Apart from nursing activities, people working as educational staff are also involved in teaching, but unlike regular teachers do not have a higher education degree in special needs education.
With regard to health-related variables we collected information on smoking status, alcohol consumption, body mass index (kg/m2 as reported by the respondents), days of physical activity per week, and whether participants ever having had a diagnosed depression. People were classified as having had a depression/depressive mood when they agreed to the statement that a physician or a psychotherapist ever diagnosed a depression or a depressive mood in the past. Concerning the body mass index (BMI), we applied the thresholds given by the World Health Organization to categorize respondents as having normal weight (BMI < 25), overweight (25 ≤ BMI < 30) or being obese (BMI ≥ 30) [13].
The work-related exposures included the duration of employment (in years), hours working per week (in hours), frequency of exposure to carrying and lifting heavy loads (> 20 kg), frequency of working in an uncomfortable position, frequency of exposure to environmental impacts (e.g. noise, heat, cold, moisture, fume, dust), and frequency of psychosocial stressors in the working atmosphere (e.g. conflicts with colleagues/superiors or bullying). The response format concerning exposure frequency comprised “frequently”, “sometimes”, “rarely”, and “never”. We subsumed “rarely” and “never” into one item category afterwards. Information on nursing activities (carrying, lifting, and transferring pupils, washing pupils, toilet assistance for pupils, changing pupils´ diapers, (un-)dressing pupils) was surveyed by asking if the respective activity is an integral part of everyday work (Yes/No).
Statistical analyses
All statistical analyses were carried out using STATA/IC 12.1 (StataCorp LP, College Station, TX). Relative frequencies were calculated for a general description of the sample. In order to identify influencing factors of chronic back pain we conducted several multivariable logistic regression analyses. Firstly, we carried out regression analyses adjusted for age and sex for all variables potentially associated with chronic back pain. Secondly, all variables being significantly associated with chronic back pain in the age- and sex-adjusted models were eligible to enter into a final multivariable logistic regression model. We applied backward elimination with p < 0.05 to determine the variables to retain in the final model. Age and sex were entered into the final multivariable model independent of any considerations of significance.
