The association between adverse ergonomic factors and work-related musculoskeletal symptoms among medical staff in China: a cross-sectional study

Abstract We investigated the prevalence of work-related musculoskeletal symptoms (WMSs) among medical staff and evaluated the associations of different levels of adverse ergonomic factors with WMSs. A total of 6099 Chinese medical staff were asked to complete a self-reported questionnaire to assess the prevalence and risk factors of WMSs from June 2018 to December 2020. A prevalence rate of 57.5% was observed for WMSs among overall medical staffs, which mainly affected the neck (41.7%) and shoulder (33.5%). ‘Keeping sitting for long hours very frequently’ (OR = 1.26, 95% CI: 1.04, 1.53) was positively associated with WMSs in doctors, while ‘keeping sitting for long hours occasionally’ (OR = 0.91, 95% CI: 0.85, 0.97) was identified as a protective factor of WMSs in nurses. The associations of adverse ergonomic factors, organisational factors, and environmental factors with WMSs were different among medical staff in different positions. Practitioner summary: We conducted a multi-city study concerning the risk factors of WMSs by carrying out a face-to-face one-to-multiple questionnaire survey among medical staff in China. As a risk factor of WMSs in medical staff, adverse ergonomic factors should be paid more attention by the standard setting department and policy makers. Abbreviations: WMSDs: work-related musculoskeletal disorders; WMSs: work-related musculoskeletal symptoms; MSDs: musculoskeletal disorders; NMQ: Nordic Musculoskeletal Questionnaires; DMQ: Dutch Musculoskeletal Questionnaires; NIOSH: National Institute for Occupational Safety and Health; ORs: odds ratios


Introduction
Work-related musculoskeletal disorders (WMSDs) are the major occupational health problem for workers in various industries (Okezue et al. 2020;Deng, He, and Li 2021;Maduagwu et al. 2022).Medical staff are exposed to severe adverse ergonomic factors, such as irregular repetitive operation, poor work postures, and heavy physical work which could contribute to the musculoskeletal disorders in different parts of body (Soylar and Ozer 2018;Yamalik 2007;Nankongnab et al. 2021).It is reported that WMSDs can cause absenteeism, sick leave, and work restriction which lead to poor quality of life as well as work among medical staff (Hafner, Milek, and Fikfak 2018;Zhang et al. 2018;Yan et al. 2018).Work-related musculoskeletal symptoms (WMSs) are a series of pain and incapacity that primarily affect the body structure, such as muscles, bones, nerves, and joints (Sezer et al. 2022).Since WMSs are highly correlated with WMSDs, it is also worthwhile to investigate its associations with multiple job factors.
Nurses, as the largest occupational group in the medical profession, have been the subject of many studies suggesting that poor workload, work organisation, and work environment factors may be associated with WMSs (Almhdawi et al. 2020;Yan et al. 2017;Almhdawi et al. 2021;Almaghrabi and Alsharif 2021;Heidari et al. 2019).A recent meta-analysis including a total of 18,199 nurses indicated that rotating and irregular shift nurses are more likely than fixed day shift nurses to experience back pain associated with WMSs (OR ¼ 1.40, 95% CI: 1.19, 1.64) (Chang and Peng 2021).However, large population studies of WMSs and its associated risk factors among all health care workers are rare.Alwabli et al. (2020) reported that 209 (54.7%) of 382 health care workers from three hospitals in Saudi Arabia suffered from WMSs, with the highest prevalence among nurses (58.3%).In addition, higher exposure rates of adverse ergonomic factors were observed in participants with WMSs compared to non-WMSs participants (Alwabli et al. 2020).In an Indian population of health care workers from a tertiary hospital (n ¼ 140), the prevalence rate of WMSs was found to be 50.7%(Yasobant and Rajkumar 2014).Moreover, the development of WMSs was contributed by staying in the same posture for a long time, working in uncomfortable postures, as well as dealing with excessive patients per day (Yasobant and Rajkumar 2014).In both studies, the correlation between poor workload, work organisation, and work environment, and risk of WMSD was not established, possibly due to the relatively small sample size.Dong et al. (2019) conducted a cross-sectional study among 14,720 medical staff in eight tertiary hospitals in Shandong Province of China and indicated that a total of 8579 (58.3%) medical staff were ascertained with musculoskeletal disorders (MSDs) lasting for more than one week.Besides, workload and related adverse ergonomic factors were associated with an increased risk of MSDs (Dong et al. 2019).However, it is still not clear how the prevalence of WMSs and the associations of adverse ergonomic factors with WMSs differ among medical staff across different positions, and whether multilevel adverse ergonomic factors have different effects on WMSs.
In the present study, we hypothesised that multilevel adverse ergonomic factor may be increasingly associated with WMSs among our medical staff population.We also hypothesise that the association may vary across different positions (nurses, doctors, lab technicians, and nursing workers).The purpose of this study was to investigate the prevalence of WMSs and its association with adverse ergonomic factors among medical staff in multiple cities in China.

Study population and design
In this cross-sectional study, from June 2018 to December 2020, we adopted a multistage cluster sampling method to select all the on-duty hospital staff with more than one year of working experience in 54 hospitals (six first-level hospitals, 17 secondary hospitals, and 31 tertiary hospitals) covering seven regions and 12 provinces and cities in China, excluding the hospital staff with congenital spinal malformations or musculoskeletal injuries caused by non-occupational factors, such as trauma, infectious diseases, and malignant tumours.Among 6766 on-duty hospital staff, 6485 (response rate, 95.8%) hospital staff successfully filled out the questions for adverse ergonomics factors and WMSs; of these, we excluded 386 subjects who were not part of the medical staff (such as administrative staff and logistics staff), leaving 6099 medical staff for further analyses.The medical staff included in the study can be categorised as doctors (including surgeons, physicians, dentist, and physiotherapist), nurses, lab technicians, and nursing assistants.The study passed an ethical review organised by the National Institute of Occupational Health and Poisoning Control, Chinese Centre for Disease Control and Prevention.

Data collection
An electronic version of the Musculoskeletal Disorders Questionnaire created and modified by Yang et al. from the Occupational Health and Poison Control Institute of the Chinese Centre for Disease Control and Prevention was used to assess the prevalence of WMSs in all medical staff (Yang et al. 2009).The questionnaire which originated from Nordic Musculoskeletal Questionnaires (NMQ, inquiring about WMSs) (Kuorinka et al. 1987) and Dutch Musculoskeletal Questionnaires (DMQ, inquiring about WMSs and related risk factors) (Hildebrandt et al. 2001) were modified according to the national conditions of China and the experience of the domestic experts.There are four sections in questionnaire that contains demographic information, musculoskeletal symptoms of different body parts (neck, shoulder, upper back, lower back, hand or wrist, leg, knee, foot or ankle, and elbow), adverse ergonomic factors, and work-related factors.The case diagnosis information was collected by asking the following questions: (1) 'In the past year, have you had any symptoms of pain or discomfort in different body parts lasting for seven days'; (2) 'Whether the pain or discomfort is caused by the current job'.These two questions concerning disease diagnosis were obtained from the US National Institute for Occupational Safety and Health (NIOSH) for musculoskeletal injury (Salvendy 2012).The relationships between adverse ergonomic factors and WMSs were assessed by this specially designed questionnaire.The questionnaire was proved to have good reliability (with Cronbach's a coefficient of the questionnaire being 0.52-0.92)as well as structural validity (with the variances of common factors being >0.4,explaining 55.17% of the total variance) in Chinese (Du et al. 2012) and has been widely used in Mainland China (Deng, He, and Li 2021;Dong et al. 2019;Zhang et al. 2020).We gathered the on-duty hospital staff on the day of the survey for one-to-multiple guidance to fill out the questionnaire, which helped the respondents to correctly understand and answer the questions.Quality control including supervision and question answering was carried out by investigators who were trained in National Institute of Occupational Health and Poison Control, Chinese Centre for Disease Control and Prevention.At the guidance site, the questionnaires were posted online through WeChat quick response code.The respondents filled out the questionnaire under one-to-multiple field guidance and online guidance of the electronic questionnaire so that we could collect the questionnaire data in good quality.

Statistical analysis
A total of 6099 valid questionnaires were included in the data analyses which performed with SAS version 9.4.Measurement data was described with mean and standard deviation.Chi-square tests were applied to compare the prevalence of WMSs among different participants in different body parts.Logistic regression models were used and adjusted for sex (male and female), age, type of work (nurses, doctors, lab technicians, and nursing assistants), BMI (<18.5, 18.5-23.9,and �24.0), current working experience (refers to the number of years of working from the date of working in the current position to the present day, categorised as 1-5, 6-10, and >11 years), working experience (refers to the total number of years of working from the date of starting the job to the present day, categorised as 1-5, 6-10, 11-15, and >16 years), education level (high school and below, college, and postgraduate and above), marital status (unmarried, married, and widowed or separated), physical exercise (never, sometimes, 2-3 times per month, 1-2 times per week, and >2 times per week), and hospital level (first-level, secondary, and tertiary hospital) to estimate the associations of adverse ergonomic factors, organisational factors, and environmental factors with WMSs.Odds ratios (ORs) with a 95% confidence interval (95% CI) were computed as the estimates of the relative risk of WMSs.All statistical analyses were two sided and pvalue <0.05 was considered statistically significant.

Characteristics of the study population
The general characteristics of the study population are summarised in Table 1.A total of 6099 medical staff ).Among all participants, 3895 (63.9%) were nurses, 1709 (28.0%) were doctors, 139 (2.3%) were lab technicians, and 356 (5.8%) were nursing assistants.Furthermore, 76.4% of the participants had working experience <15 years, and 63.5% of the respondents have been working in their current working position for <10 years.Medical staff included in the present study were mostly married (67.3%) and well-educated (95.6% with a college degree or above).
The majority of the medical staff [n ¼ 4919 (80.6%)] never or rarely do sports.

Prevalence of WMSs among different types of medical staff
Table 2 shows the prevalence rates of WMSs in various parts of the body among different types of medical staff.The prevalence of WMSs for any body region was 57.5% for overall participants, with different positions in descending order of nurse (59.3%), doctor (54.8%), nursing assistant (53.1%), and lab technician (52.5%).Among all the body parts, the prevalence of WMSs for the neck and shoulder were the top two highest.In the overall population, upper back (22.7%) and lower back (26.3%)pain were also reported, meanwhile, about one in nine to one in six participants suffered from hand or wrist (11.8%), leg (17.4%), knee (14.3%), and foot or ankle (16.5%) injury.Besides, the elbow (6.9%) was the least indicated body site.Apart from the elbow, the prevalence of WMSs were different across positions for the rest of the body parts (chi-square value ranging from 8.749 to 82.023, p < 0.05).

Adverse ergonomic factors and WMSs
The associations between ergonomic risk factors and WMSs are shown in Table 3.After adjusting for the covariates, the adjusted ORs (Table 3) were in good agreement with the crude ORs (Table S1).For overall participants, 'keeping standing (OR ¼ 1.

Organisational factors, environmental factors, and WMSs
The effect of organisational factors and environmental factors on WMSs is presented in Table 4.The adjusted ORs (Table 4) were generally robust compared to the crude ORs (Table S2).For nurses and doctors, 'working for more than 40 h per week' was positively associated with WMSs whereas 'completing work alternatively with coworkers' was a protective factor of WMSs.However, 'work at the same place' was a risk factor of WMSs for nurses but not for doctors.As for environmental factors, we found that 'feeling coldness in work place' (OR ¼ 1.16, 95% CI: 1.09, 1.22) was identified as a risk factor for WMSs in nurses.Nonsignificant  For each adverse ergonomic factor, n represents the number of people in different levels (never, sometimes, frequently, and very frequently), which, when added, equals the total number of people in that certain population.This explanation also applies to Table 4 and Tables S1 and S2.associations were observed for all organisational factors and environmental factors neither in lab technicians nor nursing assistants.

Discussion
The results of this study indicated that WMSs mainly affected the neck and shoulder among Chinese medical staff.The prevalence of WMSs and WMSs in different body parts (including lower back, leg, knee, foot or ankle, and hand or wrist) were significantly different across positions.Regarding adverse ergonomics factors, 'keeping sitting for long hours very frequently' was positively associated with WMSs in doctors, while 'keeping sitting for long hours occasionally' was identified as a protective factor of WMSs in nurses.As for organisation and environmental factors, 'completing work alternatively with coworkers' was a protective factor of WMSs in doctors, while 'working for more than 40 h per week' and 'feeling coldness in work place' were positively associated with WMSs in nurses.
Our study demonstrated that WMSs are widespread among medical staff across China, thus medical staff should pay more attention to the higher levels of adverse ergonomic factors, inappropriate organisational factors, as well as poor work environment to reduce and prevent WMSs.We found that the gender distribution of the medical staff in the present study is comparable with other previous multi-region studies of medical staff in China (Zhou et al. 2018;Su et al. 2021).Cao et al. and Tang et al. found that 96.7 and 96.3% of the nurses were female, which were both comparable to our study population (98.3%) and were representative of the overall Chinese nurses (Cao et al. 2021;Tang et al. 2022).
In the present study, the total prevalence of WMSs among medical staff was 56.7%, which was similar to the prevalence of WMSs in Saudi Arabia (54.7%),India (50.7%), and Shandong Province, China (58.3%) (Alwabli et al. 2020;Yasobant and Rajkumar 2014;Dong et al. 2019).Many studies have reported great differences in the prevalence of WMSs in nurses all over the world (Soylar and Ozer 2018).The prevalence rate of WMSs in nurses was 56.7% in our study, which was higher than the nurses in the United States (47.4%) (Zhang et al. 2018), but lower than the nurses in Lebanon (71.3%) (Younan et al. 2019), Saudi Arabia (85.5%) (Almaghrabi and Alsharif 2021), Jordan (91.0%) (Almhdawi et al. 2021), and Malaysia (97.3%) (Krishnan, Raju, and Shawkataly 2021), probably because the difference in workloads, organisational factors, and working environment factors between countries.The top three highest prevalence rates of WMSs in nurses were observed in the neck, shoulder, and lower back in the present study, which is similar to several previous studies (Yan et al. 2017;Almhdawi et al. 2021;Ou et al. 2021), indicating that the nurses had heavy burden of high pressure and poor posture in these body parts.Similarly, the doctors in hospital also seriously suffered from WMSs (Oude Hengel, Visser, and Sluiter 2011;Alnaser, Almaqsied, and Alshatti 2021;Wang, Cui, et al. 2017;Lave et al. 2020;Epstein et al. 2018), mainly involving neck, shoulder, and lower back (Smith et al. 2006;Szeto et al. 2009;Gadjradj et al. 2020;Mavrovounis et al. 2021), which is comparable to the present study.Besides, we also found that nurses had higher prevalence of WMSs for the lower parts of the body, such as lower back, leg, knee, and foot or ankle than doctors, probably due to the longer standing hours in nurses' daily work than doctors (Yilmaz and Isik Andsoy 2022).The prevalence of hand or wrist WMSs in doctors was higher than nurses in our study, probably attributable to the fact that doctors carried more static load and force on the hands or wrists than nurses during physical examinations and surgeries (Catanzarite, Tan-Kim, and Menefee 2018).The technicians engaged in a variety of clinically relevant technical activities and may be exposed to hazards associated with the development of WMSs.According to a systematic review regarding technicians (Anderson and Oakman 2016), the prevalence rates of WMSs were 28.0-96.0%with our results falling within the range (52.5%).Technicians are consisted of a variety of professionals with different operating styles and workloads, which may account for the variation in the prevalence rates of WMSs.Many studies have indicated that WMSs in nursing assistants are most likely to involve lower back (Salmani Nodooshan et al. 2020;Haas, Hunter, and Howard 2018).The prevalence rate of WMSs in lower back among nursing assistants was 20.5% in the present study, which was similar to the nursing assistants in Iran (29.8%) (Salmani Nodooshan et al. 2020), but lower than the nursing assistants in Thailand (82.0%) (Chanchai et al. 2016).This may be attributed to the difference in job duties in different countries.As for other industries, such as construction, the incidence rate of WMSs among construction workers in the United States during 2011-2014 was 39.5% (mainly involving the back and upper extremities), which is lower than in our study population (Wang, Dong, et al. 2017).
In previous studies, adverse ergonomic factors, such as working in uncomfortable posture (Rafeemanesh et al. 2021), repetitive operation (Gurgueira and Alexandre 2006), operating with hands or arms, handling tasks (Pompeii et al. 2009), using vibrators (Michalak-Turcotte 2000), as well as standing (Dong et al. 2019) and kneeling for long hours (Spector, Adams, and Silverstein 2011) at work were positively associated with WMSs in medical staff, which are consistent with our findings.Moreover, in consistent with our study population, 'awkward postures', 'working against force or vibration', and 'manual materials handling' were all risk factors for WMSs among male construction workers in Nigeria (Ekpenyong and Inyang 2014).Interestingly, 'keeping sitting for long hours occasionally' was identified as a protective factor of WMSs for nurses, since nurses often stand for long period at work, suggesting that nurses were alternated between positions, which may relieve the burden of staying in one position for a long time.For doctors, however, 'keeping sitting for long hours very frequently' was considered as a risk factor of WMSs, indicating that doctors also need to pay attention to the switch between standing and sitting posture while working.These results suggested that we should pay more attention to various adverse ergonomic factors and establish specific protective strategies to reduce WMSs in medical staff.
In our study, 'completing work alternatively with coworkers' tended to be inversely associated with decreased risk of WMSs in nurses (p ¼ 0.058), which is somewhat consistent with the significant positive association between 'not enough staff' and WMSs in a previous epidemiological study conducted among nurses in Saudi Arabia (Attar 2014).As for working hours, 'working for more than 40 h per week' were positively associated with WMSs both in nurses and doctors, probably due to the excessive workload caused by the large amount of patients in the hospital in China (Dong et al. 2019;Attar 2014;Dehghan et al. 2016;Lee et al. 2018).Besides, the association between 'working for 40 h per week' and WMSs was nonsignificant in nurses and doctors, indicating that proper working hours may reduce the occurrence of WMSs among medical staff.In this study, 'contacting frequently with patients' tended to be positively associated with WMSs in nurses.According to Milhem et al., 'direct contact with patients' was positively associated with WMSs in health care workers because of their operational needs and posture maintained throughout the working day (Milhem et al. 2016), which is comparable to our results.Possible explanation may involve that 'frequent and direct contact with patients' may cause a great deal of work stress and mental strain.'Feeling coldness in work place' was considered as a risk factor for WMSs for nurses in our study, which was similar to the results obtained from operating room nurses in Italy (Clari et al. 2019).Our findings suggested that it is necessary to provide appropriate organisation management and comfortable working environment for medical staff to reduce WMSs.
The National Plan for Prevention and Control of Occupational Diseases in China from 2021 to 2025 indicated that the research on the mechanism of occupational health damage for a series of diseases, such as WMSDs is warranted.WMSDs has not been included into occupational diseases in China, and a series of nationwide population data are urgently needed to study the determination, diagnosis, and compensation standards of WMSDs.Medical staff is a very typical occupational group, and the standardised prevalence rate of musculoskeletal injury is the second highest in China, second only to flight attendants (Jia et al. 2021).After identifying the corresponding risk factors for WMSs, some of them can be improved by strengthening relevant education and training, developing ergonomic guidelines for medical staff to prevent musculoskeletal injuries, and improving the ability of personal protection, while others (such as some postural loads, heavy lifting, and the use of vibration absorbing tools) cannot be improved by managing ergonomics.We hope that more optimised working tools can be provided to medical staff through interdisciplinary cooperation with researchers engaged in ergonomics.
Our study has certain limitations.Firstly, we defined the outcome as any symptom at any body parts and were not able to provide detailed risk factors for certain body part, which makes it not easy to find specific solutions to manage WMSDs.We will consider to further breakdown the data to finer details to evaluate the risk factors to body part relationships.Moreover, although a multi-city cross-sectional study in China was conducted to acquire more representative information and estimate WMSs prevalence among medical staff, we were not able to provide evidence of causal relationships between adverse ergonomic factors, inappropriate organisational factors, as well as poor work environment and WMSs.Besides, recall bias on different levels of exposure may lead to exposure misclassification.Finally, it is inevitable for self-reported questionnaire to result in measurement errors.

Conclusions
In a relatively large population of medical staff, the present study using questionnaire survey to obtain the prevalence rate of WMSs, as well as evaluating the associations between adverse ergonomic, organisational, and environmental factors and WMSs.Our findings suggested that WMSs are widespread among Chinese medical staff and that the neck and shoulder were the two most affected body parts.The effects of adverse ergonomic factors, inappropriate organisational factors, and poor environmental factors on WMSs were different among medical staff in different positions.Our results could be applied to guide the establishment of preventive measures, such as conducting ergonomic training, optimising work organisation, and improving working environment.Further studies investigating WMSs in certain body parts and conducting related intervention studies concerning management systems and ergonomic tools among medical staff are warranted.

Table 1 .
Basic characteristics of participants in hospital (n ¼ 6099).

Table 2 .
The prevalence rate of work-related musculoskeletal symptoms (WMSs) and its difference among different participants in different body parts.
WMSs: work-related musculoskeletal symptoms.a p-Value of chi-square.p-Values with statistical significance (p < 0.05) are presented in bold.

Table 3 .
Adjusted odds ratio [OR (95% CI)] for associations between adverse ergonomic factors and the risk of work-related musculoskeletal symptoms among all medical staff, nurses, doctors, lab technicians, and nursing assistants.
OR: odds ratio; CI: confidence interval.a , age, type of work, BMI, current working experience, working experience, education, marital status, physical exercise, and hospital level.ORs with statistical significance (p < b Adjusted for sexc Adjusted for covariates in model B, expect for type of work.ORs with statistical significance (p < 0.05) are presented in bold.

Table 4 .
Adjusted odds ratio [OR (95% CI)] for associations between factors of work organisation, work environment, and the risk work-related musculoskeletal symptoms among medical staff., type of work, BMI, current working experience, working experience, education, marital status, physical exercise, and hospital level.ORs with statistical significance (p < OR: odds ratio; CI: confidence interval.a Adjusted for sex, ageb Adjusted for covariates in model A, expect for type of work.ORs with statistical significance (p < 0.05) are presented in bold.