Evaluation of the prevalence of musculoskeletal symptoms, presumptive diagnosis, medical care use, and sick leave among female school meal service workers

Musculoskeletal disorders are the most common occupational diseases. In Korea, musculoskeletal disorders accounted for about 10% of all occupational diseases in the 1990s. In 2003, however, it accounted for 49.6% of all occupational diseases. Since 2006, it has consistently accounted for 60–70% of all occupational diseases. Of the 4947 workers, 76.64% of men and 20.36% of women were compensated for musculoskeletal diseases, according to workers’ compensation statistics from Korea Workers’ Compensation & Welfare Service in 2016 [1].

However, the burden of musculoskeletal disease in the general population is higher in women than in men. According to a study conducted in South Korea, back pain ranked first among the 30 major diseases in women and second in men based on the estimated disability-adjusted life years [2]. Another study conducted on a 20-to-64-year-old working population using the database of the National Health Insurance Service in South Korea reported that the total loss due to musculoskeletal diseases in men in 2008 was $16.74 billion and that of women was $32.09 billion. The productivity loss was $750 million for men and $1.53 billion for women [3].

South Korea’s public schools have been providing school meals for students since 2003. As a result, the number of school meal service workers had increased dramatically; most of them were middle-aged women. This job was easily accessible to individuals without a career because of similarities with housework. Hence, school meal workers have been exposed to musculoskeletal risk factors such as manual handling, repetitive motion, and awkward posture. Because older female workers performed high burden work, they had higher incidence of musculoskeletal diseases.

In this study, the musculoskeletal diseases of female school meal workers experiencing the highest level of physical burden were evaluated. Furthermore, details regarding the burden of musculoskeletal disease among female workers are limited. Some studies showed the prevalence and major site of musculoskeletal disorders among school meal service workers [4–8]. However, these studies did not provide sufficient information since they only used the musculoskeletal symptom questionnaire. Hence, this study aimed to investigate the presumptive diagnosis, medical care use, and sick leave rate of musculoskeletal diseases based on the physical examinations and history taking of occupational physicians. It also aimed to identify the risk factors for musculoskeletal disorders.

According to the results of this study, the rate of musculoskeletal symptoms among school meal workers was very high (79.5%) but relatively low compared with those reported in previous studies. Compared with the results of other studies that applied the same KOSHA criteria for musculoskeletal symptoms, the rate of subjective musculoskeletal symptom was 91.4% in a study of 326 female food service workers in Nowon-gu, Seoul [4]. In the study of 1513 female food service workers in Gangwon-do in 2012, the rate of subjective musculoskeletal symptoms was 93.4% [5]. In a study of 891 female school meal workers in Seoul in 2012, the rate of subjective musculoskeletal symptoms was 89.0% [6]. The proportion of musculoskeletal symptoms reported in an unpublished study of school meal service workers in Gwangju metropolitan city was 89.8% in 2013 [8]. It is unclear whether the relatively low rate of musculoskeletal symptoms rate in this study represents a reduction in actual musculoskeletal disease. However, since the GMOE has promoted preventive education and improvement of food service facilities, the effectiveness of these efforts may have been reflected. Nevertheless, compared with other occupations, the rate of musculoskeletal symptom among school meal workers is very high. For example, the rate of musculoskeletal symptoms among melon-cultivating farmers was 75.2% [9], and the rate of musculoskeletal symptoms among automobile engine assemblers was 42.2% [10].

According to presumptive diagnosis by physicians, myofascial pain syndrome was most common musculoskeletal disorder among school meal workers. This disorder can affect any of the skeletal muscles in the body and the prevalence varies by physician [11, 12]. The prevalence of musculoskeletal diseases affecting the upper limb was relatively higher than that in other body parts. In particular, finger- and wrist-related diseases were common. This result is similar with those reported in other studies [4, 5]. School meal service consisted of several tasks such as preprocessing, cooking, feeding, washing dishes, and cleaning the kitchen accompanied by repetitive movements, uncomfortable postures, and excessive use of force of the upper limbs. The use of relatively heavy metal plates and cooking utensils, or high intensity of kitchen cleaning for hygiene control is considered to be an additional risk factor.

In this study, the risk of musculoskeletal symptoms, presumptive diagnosis, and sick leave was significantly higher in patients older than 50 years of age, but the relative risks of musculoskeletal symptoms and presumptive diagnosis were 1.04 and 1.17, respectively. There were significant differences in the prevalence of finger joint osteoarthritis and rotator cuff syndrome by age. This result is similar with previous studies [13–15]. There are few cases of knee osteoarthritis in this study to determine whether a result is statistically significant.

By contrast, the relative risks of musculoskeletal symptoms and presumptive diagnosis by subjective physical loading were 1.45 and 2.92, respectively. According to a previous study conducted on 7100 food service workers in Japan, a large number of meals per person, insufficient rest in the morning, poor kitchen environment, and inadequate height of the countertop were significant risk factors of musculoskeletal disorders [16]. A 2-year prospective study of 385 employees in a community restaurant in Finland showed that high physical workloads play a major role in predicting the occurrence of multisite musculoskeletal pain. This study has shown that higher physical workloads have a greater impact on musculoskeletal pain incidence than individual factors such as obesity and smoking [17]. In a survey of 114 elementary school meal workers showed that age, job stress, and presence of lunchroom were not significant risk factors for musculoskeletal symptoms. However, when the number of meals per worker was over 150, the odds ratio adjusted by age, job stress, and presence of lunchroom was 4.67 (95% CI: 1.04–21.0) [8]. In a study of school meal workers in Seoul, it was concluded that job demands and stress due to physical environment were associated with musculoskeletal symptoms, with odds ratios of 3.3 and 2.5, respectively [6]. Therefore, in the case of school meal workers, the physical labor intensity is generally the most important risk factor for musculoskeletal disorders than age. The groups that responded “very high” to the physical loading showed a lower prevalence rate of rotator cuff syndrome than the group that responded “low or high”. We supposed that this phenomenon is a survivor effect, because patients suffering from this disease are no longer able to perform high-level burden work.

According to the results of this study, the prevalence of medical care use and sick leave are low considering high prevalence of musculoskeletal disorder. We supposed through interviews with school meal service worker that this phenomenon is due to a lack of alternative labor. They complained that their co-workers should have an excessive workload if they have sick leave.

This study had some limitations. First, physical loading was evaluated using a self-reported questionnaire. The number of meals per worker was widely used to identify physical loading. However, this indicator does not reflect the physical loading accurately, because food service environment varied depending on the modernization or layout of school’s kitchen, the age of the students served with meals, and additional tasks such as food preparation and cleaning. Rather, subjective physical loading can reflect this situation comprehensively. Second, there is likely to be a bias in the presumptive diagnosis of musculoskeletal disorders in this study. The six occupational physicians participating in musculoskeletal screening may have had a different experience regarding the diagnosis of musculoskeletal disorders and may have a different understanding of the diagnostic criteria. However, since most of the diagnostic criteria for musculoskeletal diseases are not clear, epidemiologic studies of musculoskeletal disorders can only be made by operational definition. In this study, the presumptive diagnosis of the physician was based on the necessity of disturbance of daily life due to pain and discomfort and the existence of objective signs. This type of diagnosis complements the limitations of subjective symptom reporting. Third, the relationship shown in this study seemed to be underestimated or overestimated due to selection bias. Therefore, other evidence is needed to determine the causality between related factors and musculoskeletal disorders. However, musculoskeletal diseases have a long prevalence duration, and there is short latency period between the exposure to the harmful factors and the onset of the disease; hence, even a cross-sectional study can be one of evidence for judging the causal relationship.

The strength of this study was the large number of participants. In addition to the subjective symptoms assessed using a questionnaire, the results were obtained through doctors’ surveys and physical examinations, as well as assessing the burden of diseases such as hospital use and sick leave.

In this study, the musculoskeletal symptoms were investigated using questionnaires and by conducting physical examinations of school meal workers. The rate of musculoskeletal symptoms was 79.6%; musculoskeletal patients, 47.6%; medical care use for 7 days or more, 36.4%; and sick leave, 7.3%. It is confirmed that the level of subjective physical loading is an important factor in developing musculoskeletal diseases rather than the age of school meal workers.

These results suggest that it is important to reduce physical burden, especially the upper limb physical burden for prevention of musculoskeletal diseases among food service workers.