musculoskeletal disorders ( msd ) are considered a work - related burden for occupational societies and national health policymakers . occupational specialists try to find accessible and feasible preventive programs to control its burden ( 1 - 6 ) . msd impacts the industries more than the workers , and the noted impact had been over presented in developing countries due to poor working conditions and lack of local or national effective msd preventive programs ( 7 ) . nurses are one of the at risk groups who provide direct healthcare services to patients . previous studies have reported that patient handling is a significant contributor to musculoskeletal disorders , especially in the back , neck , and shoulders regions , among the nurses and nurses aides ( 8,9 ) . physical factors such as repetitive tasks and awkward positions , and psychological factors such as work- related stress , satisfaction , and burnout had been reported in the previous studies as contributing factors more than age , gender , and psychological characters as personal risk factors in developing msd in workers at their workplace ( 7,10,11 ) . most previous studies in this filed focused on back injuries and musculoskeletal disorders of workers in the healthcare ( 12,13 ) and other industries ( 6,14 - 16 ) . despite these facts , few studies have examined which of the wide spectrum of risk factors are predictive of msd in the nursing profession . it is important for the policymakers to investigate factors that relate to msd among the nurses and take the necessary measures to prevent such conditions to protect nurses health and the quality of the healthcare services they provide to patients . despite their large demographic and associated potential for occupational health problems , few epidemiological studies have investigated msd risk factors among iranian nursing professionals ( 6,8,9 ) . the present study was performed to assess the role of work- related physical and psychological factors on prevalence of neck / shoulder complaints among iranian nurses in 10 main hospitals in tehran . the present cross - sectional study was conducted on nurses of 10 hospitals of iran university of medical sciences in tehran that provided special and super special healthcare services to patients from march 2014 to march 2015 . the study protocol was approved at research ethical committee of iran university of medical sciences . the participants were selected from all of the nurses of the studied hospitals according to their bed and number of patients via stratified sampling . then the study samples were selected through simple random sampling within each stratum . according to the sample size formula ( p=0.5 , d=0.005 and =95% ) , we need 384 nurses , and we added around 30% as a fraction rate ( due to non - attendance and other causes ) , and finally we included 512 nurses . the participants had at least a year of job experience without any history of primary lesions in their musculoskeletal system including neck , shoulder , lumbar , and upper and lower limbs . firstly , we used the nordic musculoskeletal questionnaire ( nmq ) to determine the prevalence of neck and shoulder complaints among the participants . nmq was developed from a project funded by the nordic council of ministers ( 17 ) . the aim was to develop and test a standardized questionnaire methodology , allowing the comparison of low back , neck , shoulder , and general complaints to be used in epidemiological studies . the nmq has been used in several studies to evaluate musculoskeletal problems including computer and call center workers ( 19 ) , car drivers ( 20 ) , and coopers industry ( 21 ) . previous studies reported that the nmq is repeatable , sensitive , and useful as a screening and surveillance tool . however , medical examination is essential to establish a clinical diagnosis ( 22,23 ) . we used job content questionnaire to assess the role of physical and psychological factors on the prevalence of neck and shoulder complaints among the nurses . job content questionnaire had some subdomains in assessing the role of work- related psychological and physical components . in the noted questionnaire , 12 questions were related to physical and 8 to psychological components . answers to questions of physical components were scored in 2 levels between 0 and 12 . finally , the scores of physical components were divided into 2 groups of low / middle physical pressure ( 0 - 9 ) , and high physical pressure ( 10 - 12 ) . we divided psychological scores into 2 groups of low psychological pressure ( 0 - 5 ) , and high psychological pressure ( 6 - 8 ) ( 24,25 ) . job contents questionnaire had a valid persian version with cronbach alpha of between 0.64 and 0.85 ( 26 ) . mean / standard deviation and frequency / percentages were used for descriptive analysis of qualitative and qualitative variables , respectively . independent sample t - test was used to compare qualitative variables , and chi - square test was used for the statistical analysis of qualitative variables . firstly , we used the nordic musculoskeletal questionnaire ( nmq ) to determine the prevalence of neck and shoulder complaints among the participants . nmq was developed from a project funded by the nordic council of ministers ( 17 ) . the aim was to develop and test a standardized questionnaire methodology , allowing the comparison of low back , neck , shoulder , and general complaints to be used in epidemiological studies . the nmq has been used in several studies to evaluate musculoskeletal problems including computer and call center workers ( 19 ) , car drivers ( 20 ) , and coopers industry ( 21 ) . previous studies reported that the nmq is repeatable , sensitive , and useful as a screening and surveillance tool . however , medical examination is essential to establish a clinical diagnosis ( 22,23 ) . we used job content questionnaire to assess the role of physical and psychological factors on the prevalence of neck and shoulder complaints among the nurses . job content questionnaire had some subdomains in assessing the role of work- related psychological and physical components . in the noted questionnaire , answers to questions of physical components were scored in 2 levels between 0 and 12 . finally , the scores of physical components were divided into 2 groups of low / middle physical pressure ( 0 - 9 ) , and high physical pressure ( 10 - 12 ) we divided psychological scores into 2 groups of low psychological pressure ( 0 - 5 ) , and high psychological pressure ( 6 - 8 ) ( 24,25 ) . job contents questionnaire had a valid persian version with cronbach alpha of between 0.64 and 0.85 ( 26 ) . independent sample t - test was used to compare qualitative variables , and chi - square test was used for the statistical analysis of qualitative variables . finally , from 512 distributed questionnaires among the study nurses , 405 questionnaires came back to the investigators ( response rate : 79% ) . meansd of age and job experience among the study participants were 426.5 ( range : 22 - 60 ) and 20.76.5 ( range : 2 - 40 ) years , respectively . meansd of bmi among the participants was 25.9 9.31kg / m ( 15.8 - 49 ) . the prevalence of neck and shoulder complaints among the nurses was 21% and 21.5% in the recent week , and 32.6% and 29.9% in the recent year , respectively . the prevalence of neck pain in the female nurses was significantly higher than in male nurses ( 37.5% vs. 27.4% ; p=0.03 , or : 1.58 , 95% ci:1.04 - 2.42 ) . the prevalence of neck complaint in the recent year was not statistically significant among the married and single nurses ( 33.1% vs. 17.6% ; p=0.4 ) . the prevalence of neck complaints was similar between nurses of special and super special hospitals ( 34% vs. 31.2% ; p=0.55 , or:0.88 , 95% ci:0.58 - 1.33 ) . the prevalence of shoulder pain among the female nurses was significantly higher than in the male nurses ( 35.1% vs. 24.3% ; p=0.01 , or:1.68 , 95% ci:1.09 - 2.59 ) . the prevalence of shoulder complaint in the recent year was not statistically different between the married and single nurses ( 31.1% vs. 5.9% ; p=0.03 ; or:5.28 , 95% ci:0.78 - 35.59 ) . the prevalence of shoulder complaints was similar in the nurses of special and super special hospitals ( 29.5% vs. 30.2% ; p=0.87 , or:1.03 , 95% ci:0.68 - 1.58 ) . the mean of age and work experience among the nurses with neck or shoulder complains was significantly higher than in nurses without neck or shoulder complaints . the mean of bmi and work hours per week was not significantly different between the nurses with and without neck or shoulder pain in the last year ( table 2 ) . 
 
 among the nurses , 88.6% and 11.4% had low and high physical workload , respectively . with respect to psychological workload , 75.8% and 24.2% of the nurses had low and high psychological workload in their workplaces , respectively . the mean of age , bmi , work experience , and working hours per week was not significantly different between the nurses with low and high physical and psychological workload . the prevalence of neck complaints among the nurses with high physical workload was significantly higher than in nurses with low physical workload ( 52.1% vs. 30% ; p=0.11 , or:2.5 , i95% c:1.37 - 4.74 ) . unlike physical workload , the prevalence of neck complaints was not significantly different between nurses with low or high psychological workload ( 38.7% vs. 30.6% , p=0.12 ) . the prevalence of shoulder complaints among the nurses with high physical workload was significantly higher than in those nurses with low physical workload ( 50% vs. 27.2% ; p=0.02 , or:2.6 , 95% ci : 1.44 - 4.99 ) . unlike physical workload , the prevalence of shoulder complaints was not significantly different between the nurses with low or high psychological workload ( 36.1% vs. 27.5% , p=0.11 ) . the results of logistic regression model in our study revealed that among the included variables , only female gender ( or:2.2 , 95% ci:1.3 - 3.7 ) and high physical workload ( or:1.2 95% ci:1.06 - 1.3 ) had an independent impact on the prevalence of neck complaints . moreover , female nurses ( or:2.8 95% ci:1.7 - 4.8 ) and those nurses with high physical workload ( or:1.2 , 95% ci:1.07 - 1.32 ) were independent predictors of shoulder complaints among the nurses . the prevalence of neck and shoulder complaints among the nurses with high physical workload was significantly higher than in nurses with low physical workload . unlike physical workload , the prevalence of neck and shoulder complaints was not significantly different between the nurses with low or high psychological workload . the prevalence of neck and shoulder complaints among the female nurses was significantly higher than in the male nurses . in our study , only the female nurses with high physical workload were independent predictors of neck and shoulder complaints . our study was designed to find the relations between neck / shoulder complaints and job demand among the nurses working in several hospitals with different work tasks . our findings can help accept our hypothesis :  increase in job demands , especially workload is associated with neck and shoulder complaints among nurses  . in a similar study in nigeria , an increase in prevalence of musculoskeletal complaints similar results were found in nurses in american ( 28 ) and chinese ( 29 ) studies . the present study revealed that neck and shoulder pain was highly prevalent among the nurses . neck and shoulder pain among the nurses might be due to recurrent lifting of heavy weights that these nurses experience in some hospital wards such as emergency situations while helping patients to be positioned on examination tables or preventing their falls ( 28,29 ) . in our study , a strong association was found between the job demands and physical workload with musculoskeletal symptoms . on the other hand , the nurses with higher physical workload had significantly higher neck and shoulder complaints compared to other nurses . our findings were similar with those of the previous studies on musculoskeletal disorders ( 30 - 32 ) and physical and mental health outcomes ( 33 - 36 ) . first , due to the cross- sectional design of the study , we could not establish causal relationships between the study variables . second , the relatively small sample size and potential selection bias might have also limited the validity and generalizability of the study findings to iranian nurses as a national finding . third , our analysis was based on self - report measures of job contents and neck / shoulder complaints . common method variance may lead to bias inflating correlations between these variables , but unfortunately , we did not assess the common method bias in our study . findings of the present study revealed that those nurses who more workload , especially physical workload , had a higher prevalence of neck and shoulder complaints and this fact could impact their work tasks . conducting a longitudinal design to confirm our interpretation and use them in national preventive programs for healthcare workers is highly recommended .
background : identifying the predisposing factors of neck and shoulder complaints and finding solutions to avoid them could improve the occupational health condition of the nurses . in this study , we aimed at determining the role of psychological and physical occupational factors in developing neck and shoulder complaints among the participants . 
 methods : this analytic cross - sectional study was conducted on the nurses of main hospitals of tehran . to study the prevalence of neck and shoulder pain , 
 the nordic questionnaire was used , and job content questionnaire was used to assess the psychological and physical occupational factors . 
 data were analyzed using spss and statistical methods . 
 independent sample t - test was used to compare the qualitative variables , and chi - square test was utilized for the statistical analysis of the qualitative variables . 
 results : prevalence of neck and shoulder complaints among the nurses with high physical workload was significantly higher than in those nurses with low physical workload . unlike physical workload , the prevalence of neck and shoulder complaints was not significantly different between the nurses with low or high psychological workload . 
 prevalence of neck and shoulder complaints among the female nurses was significantly higher than in the male nurses . in our study , only female nurses with high physical workload had been known as independent predictors of neck and shoulder complaints . 
 conclusion : those nurses who had more workload , especially physical workload , had a higher prevalence of neck and shoulder complaints , and this fact could affect their work tasks .