Participants and data collection
The Gwangju Metropolitan Office of Education (GMOE) conducted a screening program for prevention of musculoskeletal diseases among 1930 school meal employees from February to December 2016. The health examination of musculoskeletal disease was requested to three hospitals with occupational and environmental medicine departments. A total of 1581 (82%) individuals participated in this screening program. We obtained a written consent from all participants, which permits the use of collected data for preventive action. We retrospectively analyzed the data of the GMOE’s musculoskeletal disease screening program. This study was approved by the Institutional Review Board (Chosun 2018–05-015).
Research tools
General characteristics and occupational characteristics
Variables were collected using the musculoskeletal symptom questionnaire developed by the Korea Occupational Safety and Health Agency (KOSHA) [9]. The variables consisted of job control, household work time, current illness, injury experience, current illness, injury experience, working hour, the number of meals per day, career of school meal service worker, type of school, and subjective physical loading. Job control is categorized based on whether it can control work speed and break time. Household work time refers to the average time spent performing certain tasks such as cooking, washing, cleaning, and taking care of children under 2 years old at home and is categorized by a 2-h cut-off. Current illnesses mean diagnosis of diseases such as rheumatoid arthritis, diabetes, lupus disease, gout, and alcoholism by physicians. Moreover, they developed hand, finger, wrist, arm, elbow, shoulder, neck, waist, leg, and feet injuries due to exercise-related accidents, traffic accidents, falls, and crash. Subjective physical loading was assessed on a five-point scale (very low, low, slightly hard, hard, and very hard) based on the physical burden felt for current work and was categorized into three levels by combining “very low,” “low,” and “slightly hard” into “low.”
Four outcome indicators of musculoskeletal diseases
To investigate the characteristics of musculoskeletal diseases in female school meal workers, the four outcome indicators were categorized as follows: subjective musculoskeletal symptoms, presumptive diagnosis, the rate of hospital visits over 7 days during the past 12 months, and the rate of sick leave during the past 12 months. The subjective musculoskeletal symptoms were defined as pain that developed more than once per month or pain that lasted more than 1 week, which was assessed using the musculoskeletal symptoms questionnaire from KOSHA [4]. The presumptive diagnosis was defined as being diagnosed and treated as a musculoskeletal disease by a doctor or having severe pain and objective signs upon physical examination. Severe pain was characterized by difficulty sleeping and restricted work performance or limited performance of daily activities. Pain severity was assessed by the doctor through history taking. Objective signs on physical examination were defined as positive response in provocation test, tenderness, and limited range of joint motion.
The detailed diagnosis of musculoskeletal disorders was made based on the following criteria. Myofascial syndrome has pain on the affected muscle or referred pain, tenderness, taut band, and pain during contraction. Finger joint osteoarthritis has joint stiffness or pain during joint motion and limited range of joint motion, Heberden’s node, Bouchard’s node, and joint swelling. Elbow epicondylitis has pain and tenderness in the medial or lateral epicondylar area without neurological symptoms and symptom induced by resistance against bending and extension of the wrist. Rotator cuff syndrome has no abnormal sensation in the corresponding shoulder area, but the pain is present with a positive sign in empty or full can test, impinge (Neer sign and Hawkins-Kennedy test) test, resisted internal rotation test, external rotation test, or lift-off test. Carpal tunnel syndrome is marked by intermittent sensory disorders or pain in the first, second, third, and fourth fingers and pain in the wrist and palms or radiating pains in the proximal part of the wrist. Phalen’s test, Tinel’s test (percussion), and wrist compression test revealed positive results. Finger tenosynovitis is marked by pain when moving the tendon and tenderness when palpating the tendon. Lumbar radiculopathy is characterized by leg pain, numbness, difficulty in walking, positive straight leg raising test, positive Lasegue sign, sensory changes in the specific site, or decline in motor function. Cervical radiculopathy is marked by intermittent pain and neck stiffness. With regard to head movement, an abnormal sensation or pain is felt that stretches from the neck to the upper limb. A pain is felt in the upper extremity during active or passive neck rotation and the result of Spurling test is positive. Knee osteoarthritis is characterized by knee pain in individuals older than 40 years of age, morning stiffness in the knees with bone spurs quadriceps muscle atrophy, or presence of varus deformity. These diagnostic criteria were shared by occupational and environmental physicians who participated in the screening.
To investigate the rate of medical care use and sick leave among workers with musculoskeletal diseases, the following question was asked: “Have you ever been absent or treated for musculoskeletal (joints, muscles, ligaments, tendons, and nerves) pain during the past 12 months (excluding accidental injuries, visits to the hospital for health checkups, and absence due to personal issues)?” Hence, we categorized medical care use and sick leave as follows: more than 7 days of medical care use and more than 1 day of sick leave.
Statistical analysis
The univariate and multivariate analysis was conducted to examine the relationship between the four outcome indicators and potential risk factors such as job control, household work time, current illness, injury experience, working hour, number of meals per day, type of school, and subjective physical loading. We compared the relative risk of each outcome indicators by log-binomial regression analysis using SAS 9.3 (SAS Institute Inc.).