Introduction 
In the past decade, occupational diseases have been prevalent in 40-60% of the workers, most of which is musculoskeletal disorders [1, 2]. Work-related musculoskeletal disorders are associated with discomfort, weakness, inability, or persistent pain in the neck, back, or upper limbs [2, 3]. The prevalence of musculoskeletal injuries is estimated to be 40% and 84% in developed and developing countries, respectively [4, 5]. Nurses, due to having repeated movements such as pushing, pulling, lifting, and bending in the workplace, are prone to a variety of musculoskeletal disorders [6]. The most common musculoskeletal disorder among nurses is low back pain with a prevalence of 32-90%, followed by neck pain, shoulder pain, and knee pain with prevalence rates of 12-52%, 17-48%, and 7-68%, respectively [7]. Musculoskeletal disorders seem to be multifactorial and has several risk factors, including physical, psychosocial, organizational and individual factors. Risk factors associated with musculoskeletal pain among nurses include high physical activity, poor posture at work, moving patients, and lifting heavy loads. Neck pain has a multifactorial etiology. Nonmodifiable risk factors of neck pain are age, gender, and genetics, while modifiable risk factors are smoking, exposure to tobacco smoke, physical inactivity, and mental health problems [8]. Due to anthropometrical and physiological sex differences, women are more prone to neck pain [9]. Genetics seem to have a role in neck pain, although its influence gradually decreases by aging and environmental factors become more predominant. Studies have shown that exposure to tobacco smoke, obesity, and high physical activity are risk factors for neck pain [9, 10]. The results of a study showed that the highest rate of musculoskeletal injuries in health care providers was due to lifting and moving patients [11]. Intensive care unit (ICU) nurses are at higher risk of developing musculoskeletal disorders than nurses working in other hospital wards [12, 13]. History of sports injury or occupational trauma, has also been reported as a risk factor for chronic neck pain [14]. Mental problems such as anxiety and anger in case of neck pain have been shown to be associated with a weaker prognosis [15]. Musculoskeletal disorders are the second leading cause of occupational disability and absence from work after cold, which can force hospital nurses to change their career and can impose high economic burden on the health care system [16]. Due to the limited research on this issue in developing countries, especially Iran, this study aims to investigate the frequency of neck pain among ICU nurses in north of Iran and its associated factors.

Materials and Methods
This is a descriptive-analytical study with a cross-sectional design. The study population consists of the nurses working in ICUs of seven teaching hospitals in Rasht, Iran, in 2019. The sampling was done by a census method. Thus, the sample size was equal to the study population (n=145). Inclusion criteria were willingness to participate in the study, no cervical trauma or surgery in the neck area, and working in the ICU.
The data collection tool was a two-part questionnaire. The first part surveyed demographic information including age, sex, body mass index (BMI), and information about the number of work shifts per month, type of work shifts, marital status, work experience, family history of neck pain, history of exercise, and history of mental health problems. The second part was the neck disability index (NDI) developed by Vernon et al. [17]. It has 10 items rated on 6-point scale from 0 to 5, and has a total score of 50. A score of 0-4, 5-14, 15-24, 25-34, and above 34 indicate no disability, mild inability, moderate disability, severe disability and complete disability, respectively [17]. The Persian version of this questionnaire has been validated by Mousavi et al [18]. They reported a Cronbach’s α value of 0.88 for this questionnaire. The questionnaire was distributed among the participants and collected during one month (from March to April 2019). 
The recorded data were statistically analyzed in SPSS software, version 22 (IBM Corp., Armonk, NY). To investigate the difference in the prevalence of neck pain based on the sociodemographic factors, chi-square test and Fisher’s exact test were used. To determine the risk factors of neck pain among nurses, logistic regression analysis was used. Significance level was set at 0.05. 

Results
Of 145 questionnaires, 120 were completed and returned (response rate: 82.7%). Table 1 presents the characteristics of participants.


The mean age of nurses was 35.7±5.8 years and their mean work experience was 11.1±5.6 years. The overall frequency of neck pain among nurses was 82.5% (n=99), and 17.5% of patients had no disability. Among those with neck pain, 51.7% had mild disability, 26.7% had moderate disability, and 4.2% patients had severe disability.
The results in Table 2 showed that the prevalence of neck pain was not significantly different based on sex, BMI, number of work shifts per month, type of work shift, family history of neck pain, or history of mental health problems; however, it was significantly different based on age (P=0.031), marital status (P=0.012), work experience (P=0.019), and history of exercise (P=0.031).


The frequency was higher in married nurses than in single ones, and in nurses with more than 15 years of work experience. Moreover, as shown in Table 3, the frequency of neck pain severity were also significantly different based on age (P=0.001), marital status (P=0.042), work experience (P=0.006), and history of exercise (P=0.011). 


To determine the risk factors of neck pain among ICU nurses, logistic regression analysis was used. The results are summarized in Table 4.


Among the parameters of age, marital status, work experience, and history of exercise, only the history of exercise was significant predictor of neck pain in nurses. In nurses who had no history of exercises, the risk of neck pain was 3.277 times higher than in nurses with a history of exercise (OR=3.277, 95% CI; 1.30%, 10.43%, P=0.045). But at a significance level of 0.1, marital status and work experience were also independent predictors of neck pain in nurses, so that compared to single nurses, the risk of neck pain in married nurses is 2.92 times higher (OR=2.92, 95% CI; 0.9%, 9.3%, P=0.069) in borderline manner.

Discussion 
In the present study, most of ICU nurses suffered from some degree of neck pain and the majority of them had moderate or severe neck pain. We used the standard NDI questionnaire. The related studies have mostly used a researcher-made questionnaires and have reported different rate and severity of pain in nurses [19]. Our findings showed that the frequency of neck pain among ICU nurses in Rasht was significantly higher than reported rates of neck pain in the general population [9-11, 20, 21]. Joslin et al. reported that 76% of nurses had neck pain [12]. In the study by Sheikhzadeh et al., the prevalence of neck pain among surgical nurses was 71% [13]. The results of a study in Brazil showed that neck pain with a prevalence of 68% was the second most common musculoskeletal pain among nurses [22]. Habibzade et al. reported the prevalence of low back pain among Iranian nurses was 56% [23]. Kheiry et al. reported that 16.7% of nurses in Bandar Abbas had chronic neck pain [15].
In the present study, frequency of neck pain was not significantly different between males and females. It can be because of small number of male nurses in our study. Côté et al. reported that female gender was an independent risk factor for neck pain [24]. Our study showed that the frequency and severity of neck pain was significantly different based on age; it was higher in the age group of 40-49 years than in younger nurses. In our study, prevalence of neck pain was higher in obese nurses than in overweight or normal weight nurses, but the difference was not statistically significant. Frequency of severe neck pain in married nurses was significantly higher than single nurses, consistent with Afshar et al.’s study [25]. This can due to pregnancy, hormonal changes, or child care tasks added to the responsibilities of nurses. Furthermore, the overall prevalence of neck pain and severe neck pain were significantly higher among nurses with more than 15 years of work experience than in nurses with less work experience.
In the present study, although the prevalence of neck pain was higher among nurses with higher number of work shifts per month, but the difference was not statistically significant. Also, there was no significant difference between nurses with morning, evening or night shifts. An interesting finding of the present study was the difference in the prevalence of neck pain among nurses based on the history of exercise; the prevalence in nurses who had no sport activity and exercise was significantly higher. Exercise has been shown to be an effective preventive intervention in reducing musculoskeletal pain, especially in the neck and back [21, 26]. In a recent study, the results indicated high prevalence of musculoskeletal complaints in nurses working in hospitals. The posture and movements as well as the type of work can affect the prevalence in nurses [27].

Conclusion
This study showed a high frequency of neck pain among ICU nurses in Rasht, north of Iran. The risk factors were work experience >15 years, age >40 years and lack of sports activity. Therefore, it is necessary for policy makers to take the necessary measures to prevent or reduce these complications in nurses in order to protect the health of nurses and the quality of patient care. One of the limitations of this study was that the nurses answered the questions in their work environment; the workplace-related stress and pressure can affect their answers to the questions. Another limitation was the small number of male nurses. Thus, more studies in the future is needed to accurately determine the prevalence of neck pain and related factors among male nurses. Moreover, further studies with larger sample sizes and considering the ergonomic characteristics of the workplaces, postures and movements are recommended.

Ethical Considerations
Compliance with ethical guidelines
The study was approved by the Ethics Committee of Guilan University of Medical Sciences (Code: IR.GUMS.REC.1398.014). Informed consent was obtained from all participants, and they were assured of the confidentiality of their information. 

Funding
This research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors. 

Authors' contributions
Conceptualization and supervision: Ali Ashraf; Methodology: Kamran Ezzati; Data collection: Roxana Mahdavi and Sedigheh Samimian; Data analysis: Habib Eslami Kenarsari; Literature review: Kamran Ezzati; Writing the original draft: Zoheir Reyhanian; Final approval: All authors.

Conflict of interest
The authors declared no conflicts of interest.

Acknowledgments
The authors would like to thank the Clinical Research Development Unit of Poursina Hospital in Rasht, Iran, and all nurses participated in this study for their cooperation in this study.


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