Neck/shoulder pain and low back pain among school teachers in China, prevalence and risk factors

Between December 11, 2009 and March 15, 2010, seven schools were selected at random from 60 major public schools in Puning, a city in eastern Guang dong Province. Written consent was obtained from the Ministry of Education in the districts where the schools were located. This research was also approved by the Ethics Committee of the Medical College of Shantou University and the Ministry of Education of Puning. Each teacher in the chosen schools was given a consent letter and a document describing the procedure of the study and its objectives. At the weekly school teachers’ meeting, a questionnaire was administered and it took about 20 min to complete.

The demographic characteristics in the questionnaire included gender, age, height and weight. Body mass index (BMI) was calculated by the formula weight (kg)/height (meter)². Normal weight was defined as a BMI of ≤23.9 kg/m², overweight as BMI 24.0-27.9 kg/ m² and obesity as BMI ≥28.0 kg/m²[14]. Also, lifestyle (smoking, hours of housework and physical exercise per week) were surveyed. The work characteristics were assessed using questions for school level, years in current job, work hours per week, how many lessons per week and hours of working with computer per day. The questions used to assess occupational risk factors were derived from the standardized Dutch Musculoskeletal Questionnaire (DMQ) [15]. Occupational factors were measured using a dichotomous scale (No/Yes) during an average working day. Work was categorized as tasks with prolonged standing (≥2 hours per day), sitting (≥4 hours per day), static posture, working with hands above shoulder (≥2 hours per day), lifting of weight with hand ≥20kg, posture characterized by twisting posture (≥2 hours per day), uncomfortable back support, have enough rest time. The questions on musculoskeletal symptoms were assessed according to the Nordic Musculoskeletal Questionnaire (NMQ) and were accompanied by anatomical diagrams depicting the specified sites [16]. The participants were asked whether they had experienced pain in the neck or/and shoulder and low back lasting for more than 1 day during the previous 12 months.

The results were reported as descriptive statistics. Odds ratios (OR) and 95% confidence intervals (95%CI) were calculated to examine the association of NSP and LBP with demographic, individual and occupational risk factors using binary logistic regression. Initially, univariate analyses were calculated, with each of the potential explanatory variables as independent variables and NSP or LBP as the dependent variable. OR were obtained for each potential factor after adjustment for age (as a continuous variable with a unit of analysis of 1 year), and gender. In further multivariate logistic regression, non-significant variables (P > 0.05) were excluded, with the exception of age and gender, which remained in the model regardless of statistical significance. Multivariate logistic regression analyses were performed using all retained variables. The final model included terms with a P value less than 0.05. All analyses were performed using SPSS version 19.0.

The first aim of this study was to estimate the 12-months prevalence of NSP and LBP among school teachers in Puning. Our study identified 48.7% and 45.6% prevalence of NSP and LBP among teachers. Parallels can be drawn to other studies where 42.5-47.9% and 43.8-74.9% of Turkish school teachers reported having experienced neck pain and low back pain respectively, while 28.7-55.9% had experienced MSD symptoms in the shoulder area [17, 18]. In Brazil and Malaysia, 41.1% and 40.4% of elementary school teachers reported low back pain [19, 20]. Another study of Brazil obtained data showed the presence of pain in the trapezius muscle region, on the left side, in 52.5%; and, on the right side, in 50.6% among elementary school teachers [21]. Other studies where 40.0% of Chinese primary school teachers and 34.8% of French school teachers also reported back pain [7, 22]. In Chinese Hong Kong, studies of secondary school teachers reported a 12-month prevalence of neck pain at 64.4% and 66.7% [23, 24]. The disorders seem to be most common in the neck, shoulders and low back among teachers. Our results are generally consistent with these prior studies in school teachers. It is important to pinpoint hazards for developing prevention strategies.

Many individual factors including age, gender and BMI may play a role in causing NSP and LBP. Our results showed that gender and physical exercise were related to NSP. The prevalence of NSP was substantially higher among women (51.7%) than men (42.7%) in our study, which is consistent with previous studies [25, 26]. Women appear to consistently report more neck, shoulder and upper extremity symptoms than men [12, 18, 23, 24, 27, 28]. In our study, even though males had a higher BMI, longer employment than females, a significant higher proportion of smokers and often worked time >40 h, females were significantly at risk for NSP. The gender difference may be explained by many factors, one of which could be that the women had in which they were more likely suffered emotional exhaustion compared with men among teachers [29]. This may also explained partially by women having a lower pain threshold than males. Torgen et al. suggested that pressure pain thresholds increased with muscle strength and Chiu et al. found that the isometric neck muscle strength in all directions for men was 1.2–1.7 times those in women [30, 31]. Moreover, we found females bore more heavy housework than male in daily life, and some authors suggest that differentials in household task participation may explain WMSDs differences between men and women [25, 32].

Teachers at the senior middle school level reported the highest prevalence of NSP and LBP, in comparison to those at the primary and secondary school levels, which is consistent with previous studies [33]. The teachers who worked in high schools suffered significantly higher risks of NSP and LBP. One of the reasons could be that senior middle school teachers have to deal with more examinations and are under higher pressure to graduate students. So they experience more psychological stress and a higher work load than others. In the present study, teachers who worked in senior middle schools also had the highest work load in comparison to those who worked in other levels of schools. Emotional exhaustion correlates with the high numbers of weekly lessons [34]. Work activities that involve heavy lifting, awkward postures, bending, twisting or stooping, prolonged sitting or standing and repetitive motions may contribute to the development of MSD [35‐37]. Activities of sustained sitting of frequent reading, marking of assignment and in front of computer, standing up teaching in class, repetitively overhead writing on board are also unsafe act and favorable to the development of NSP, LBP and upper limb pain which found in teachers [20, 23, 38]. Studies have also confirmed that sitting for more than 3 hours daily could be a risk factor for LBP [39, 40]. But Lis and colleagues, in their systematic review, found that sitting itself does not increase the risk of LBP, but sitting for more than half a workday, combined with whole-body vibration and/or awkward postures, does increase the likelihood of having LBP, and it is the combination of those risk factors that leads to the greatest increase in LBP [41]. Epidemiological studies show a significant association among uncomfortable back support and LBP [42, 43]. Moreover, our study further confirmed these findings in school teachers. In the present study prolonged sitting and static posture and uncomfortable back support were positively associated with NSP and LBP. In addition, prolonged standing was closely associated with NSP alone.

Our data demonstrates significant school levels differences in the experience of NSP and LBP. Moreover, our data point to senior middle school teachers in which there is a very great need to study workload stress factors and devise adequate preventive and interventional action.

Our study had several limitations. Information about musculoskeletal symptoms and related factors were obtained by the self-reporting method and the nature of this retrospective questionnaire survey, it is difficult to rule out the possibility of recall bias, which may lead to over-or underestimation. Furthermore, as a cross sectional study, only associations can be established but no inferences of causality can be made.