Factors associated with neck disorders among university student smartphone users

1 Introduction

In our digital society, the use of smartphones has increased rapidly. There are 3.4 billion smartphone users worldwide [1]. Thailand is nineteenth of the top twenty-five countries worldwide in terms of smartphone use [2]. The age group of smartphone users varies, ranging from students and workers in their 20s to senior citizens who are over the age of 60 [3]. University students in their 20s, in particular, use smartphones more than any other age group [4]. Compared to general cell phones, smartphones are very sophisticated devices, offering vast amounts of information and communication, all in the palm of your hand. They have an operating system, essentially making them palmtop computers, which are more powerful, provide greater computing capacity and diverse software applications [5]. Smartphones provide various conveniences, such as sending and receiving e-mail, accessing the Internet and engaging in entertainment, so the number of smartphone users has increased dramatically in recent years [6].

However, with the growing use of smartphones, comes concerns of increased musculoskeletal problems, which are associated with intensive smartphone usage. Musculoskeletal problems are among the most common occupational disorders in many countries and have an increasing trend [7]. An epidemiological study of 938 smartphone users conducted in the Republic of Korea found that 18.8% of smartphone users (n = 185) experienced musculoskeletal symptoms in at least one of their body parts [8]. In another Korean study involving 292 smartphone users, Kim et al. [6] found the most painful body regions from smartphones use were reported to be the neck (55.8%) and shoulders (54.8 %) [9].

The results of a different study conducted in Asia with a similar survey method are from Hong Kong, where musculoskeletal disorders among smartphone users were shown to have a much higher prevalence than the Korean study conducted by Eom et al. [8]. In the Hong Kong study, 70% of respondents reported having experienced neck pain (n = 1,049), 65% had shoulder pain, 46% experienced wrist and finger pain, [10]; the reasons for the difference in the study results from Korea and Hong Kong are not clear, however, there was a considerable difference in the sample size. Nevertheless, in Thailand, musculoskeletal disorders among smartphone users, especially in university students who are in their 20s, have not yet been reported.

Previous studies have shown the risk of musculoskeletal symptoms in information technology device users, such as tablet users, is related to personal factors such as gender (OR = 2.183, 95% CI [1.276, 3.736], p = 0.004) and awkward positions like sitting in a chair without back support (OR = 2.821, 95% CI [1.341, 5.934], p = 0.006) [11]. Both risk factors, gender and awkward postures, affected the prevalence of neck (84.6%) and upper back/shoulder (65.4%) musculoskeletal symptoms. While smartphone users have different usages compared with tablet users such as posture, previous studies which used self-report methods demonstrate four individual factors associated with musculoskeletal disorders in both groups. These factors were: (i) smartphone usage, people with higher smartphone use had more severe symptoms [12]; (ii) gender, females who use smartphones had a significantly higher neck disability index score than males (p <  0.001) [13]; (iii) age of user, older persons and (iv) lack of exercise also increased the occurrence of musculoskeletal disorders [10].

Physical design factors related to the smartphone itself may also lead to smartphone users developing musculoskeletal disorders. These physical factors have been reported in many survey studies, includes: the size of smartphone liquid crystal displays (n = 292) [9], the number of text messages (relative risk = 1.425) (n = 983), the time spent on daily usage of the smartphone (relative risk = 1.368) (n = 2,353) [4, 8] and prolonged static posture during smartphone usage (n = 1,049) [10]. Several studies have reported psychosocial factors associated with smartphone use. In Korea, Hwang et al. [12] surveyed the impact of smartphone overuse on upper extremity pain, anxiety, depression, and interpersonal relationships using several questionnaires (respectively: the Smartphone Addiction Inventory, the Musculoskeletal Symptom Checklist, the State-Trait Anxiety Inventory, the Beck Depression Inventory-II, and the Relationship Change Scale). They received 525 responses from college students and findings revealed anxiety and depression to be higher in the smartphone overuse group than in the normal use group [12]. In addition, Park et al. [14] studied depression using the Beck Depression Inventory (BDI) in “heavy” smartphone users, which they defined as those who spent 5.4 hours a day on their smartphone. Their sample consisted of 20 healthy student participants and the investigators reported that smartphone use could cause negative effects on a person’s psychological status, such as depression (p = 0.006) [14].

Although it is clear that the neck is the area commonly reported to have the highest pain among smartphone users [9, 10], investigation on the ergonomic factors leading to neck pain among smartphone users remains limited [5]. Neck pain is known to be a multi factorial disorder, with head and spinal posture being one of the most important factors. Previous studies concluded that prolonged neck flexion is highly associated with neck pain both among the general population [15] and among office workers who use computers [16–18]. Similarly, the neck flexion posture is commonly adopted while smartphone users view the visual display terminals of smartphones for extended periods. Kang et al. [19] reported that this posture causes musculoskeletal problems [19]; however, the association between neck flexion during smartphone use and neck disability has not been scientifically confirmed to date. Furthermore, there are possible influential factors, which are reported to be associated with neck disorders in the general population, however, these have not been studied among smartphone users who smoke or suffer from stress.

The purpose of the current study was to investigate MSDs in smartphone users in Thailand in order to confirm high prevalence of neck pain. The study also aimed to determine all possible factors associated with neck disorders among smartphone users. The hypothesis was that ergonomic factors like neck postures are associated with neck disorders among smartphone users. The findings of this study can produce important information for exploring associations between intensive smartphone use and the occurrence of neck disorders. Additionally, the information may be used to underpin prevention and health promotion initiatives to address the risk of neck disorders associated with smartphone use.

2 Methods

3 Results

The purpose of this study was to determine associations between neck flexion postures and neck disorders among smartphone users. The current study found that smoking and neck flexion posture were associated with the occurrence of neck musculoskeletal disorders in the smartphone users.

Smoking is an important individual risk factor for neck musculoskeletal disorders [23]. It is clear that cigarette smoking has deleterious effects on the musculoskeletal system [24]. Two recent systematic reviews published by Hogg-Johnson et al. [25] and Côté et al. [26] evaluated the determinants of neck pain. The former found evidence that exposure to passive smoking in adolescents increased the risk of neck pain. The latter review summarized that smoking increased the risk of neck pain among the working population [25, 26]. The current study is the first to show smoking is a factor associated with neck disorders in smartphone users. The odds ratio for this was high because there were 11 participants who identified themselves as current smokers and 9 of them had musculoskeletal disorders in the sample of 643 participants. The Khon Kaen University is a non-smoking campus which may account for the low number of smokers in the current study. In the future, it would be useful to study a specific ‘smoker only’ group to clearly confirm this finding. In linking smoking with neck pain, clinical and experimental studies have shown that cigarette smoking induced skeletal muscle damage due to impaired muscle metabolism, increased inflammation and oxidative stress [27]. These could be affected by the occurrence of neck pain in university student smartphone users.

Neck flexion is the most common posture smartphone users adopt when looking at their smartphone visual display terminals for long duration of time and such postures may cause musculoskeletal problems [19] especially in the neck region [5]. Kim et al. [28] studied the influence of the duration of smartphone use on cervical and lumbar spine flexion angles and reposition error in the cervical spine in 18 healthy smartphone users. They measured the kinematics of the upper and lower cervical and lumbar spine flexion angles and the reposition error of the upper and lower cervical spine after 3 seconds (s) and 300 s (five minutes) of smartphone use in sitting. They reported that the flexion angles of the lower cervical and lumbar spine and the reposition error in the upper and lower cervical spine were significantly increased after 300 s of smartphone use (p <  0.05). However, the flexion angle of the upper cervical spine was not significantly different between the 3 s and 300 s smartphone of use (p >  0.05). These findings suggest that prolonged use of smartphones can induce changes in cervical and lumbar spine posture and proprioception in the cervical spine [28].

Park et al. [14] evaluated two groups of 10 healthy Korean student smartphone users based on the length of time spent on their smartphones. The researchers categorized the two groups into ‘heavy’ smartphone, defined as those who spent 5.4 hours a day on their smartphone, compared to a ‘control’ group who spent an average of 4.1 hours a day on their smartphone. The researchers measured participant craniovertebral angle, head position angle, pain threshold of the sternocleidomastoid and upper trapezius muscles, and presence of depression. They found significant differences between the groups in the pain threshold of the sternocleidomastoid and upper trapezius muscles, head position angle, and depression (p <  0.05), but not in the craniovertebral angle. Based on the results, their study showed that ‘heavy’ smartphone use may produce considerable stresses on the cervical spine, thus changing the cervical curve and pain threshold of the muscles around the neck. Smartphones could also cause negative effects on a person’s psychological status, such as depression [14].

Lee et al. [5] assessed posture during smartphone use in 18 participants in a laboratory setting. Their measurements included the amount and range of head flexion of smartphone users, head forward flexion angle while they were conducing three common smartphone tasks (text messaging, web browsing, video watching) while sitting and standing. They found that participants maintained head flexion of 33°–45° from vertical when using the smartphone. The head flexion angle was significantly larger (p <  0.05) for texting than for the other tasks, and significantly larger while sitting than while standing. Their study results suggest that texting, which is one of the most frequently used app categories of smartphone, could be a main contributing factor to the occurrence of neck pain of ‘heavy’ smartphone users [5].

Ning et al. [29] also evaluated the neck extensor muscle activities and the kinematics of the cervical spine during the operation of a touchscreen tablet and a smartphone in 14 participants. Participants of this study maintained significantly increased neck flexion angle when operating a smartphone (44.7°), with the mobile devices set on a table (46.4°), and while performing a typing task (45.6°) [23]. This study had apparently shown that during smartphone use, smartphone users also maintained their head flexion in various angles conforming to Lee et al. [13]. They also demonstrated that the magnitude of neck flexion was affected by the size of the screen, device location and the tasks performed [29]. Task influenced cervical spine posture with the highest cervical flexion occurring while completing a simulated data entry task [30]. Awkward posture like neck flexion refers to positions of the body that deviate significantly from the neutral position while tasks are being performed and it is the primary ergonomic risk factor for developing musculoskeletal discomfort [31]. In addition, elevated neck muscle activities were observed while holding mobile devices in hand (vs. putting them on a table) and elevated neck muscle activities also were observed while performing typing and gaming tasks (vs. reading task) [29]. These occurrences could be a main associated factor to the occurrence of neck pain.

Hansraj [32] assessed stresses on the cervical spine caused by posture and position of the head and reported that the weight taken by the spine dramatically increases when flexing the head forward at varying degrees. Loss of the natural curve of the cervical spine leads to incrementally increased stresses about the cervical spine [32].

In summary, all of the reasons above support the association we found in our study; that is, neck flexion postures in smartphone users are associated with the occurrence musculoskeletal disorders of the neck.

Our study is the first to examine stress in relation to neck disorders in smartphone users, and we found no association between stress and smartphone use. Previous studies of psychosocial factors revealed anxiety and depression to be higher in smartphone users [12, 14] but we are not able to comment on these individual psychosocial factors. Rather, the Suanprung Stress Test –20 that we used in our study provides a measure of stress because this test is appropriate for Thai student and adulthood [33].

Our study found the average size of smartphone liquid crystal displays was 4.46 ± 0.69 inches which is smaller than the average size of smartphones reported in previous studies [9]. It is possible that smaller screen size may relate to different neck postures to improve vision, because smaller screens will cause a deeper bending of the neck to reduce the distance between the eyes and the screen, as well as increase the clarity of vision. The deeper neck bending could be due to elevated neck muscle activities, and this will affect neck pain respectively. Mobile devices with larger screen sizes are preferable from the MSD prevention perspective. However, larger screen sizes may also increase the weight of the device, which could introduce fatigue to arm and shoulder muscles when holding these devices for prolonged periods of time [29]. And this remains to be tested in future studies. It is interesting to note that most participants in this study held their smartphones with both hands, which is a good ergonomic for smartphone users. Holding a smartphone with one hand presents a higher risk for a musculoskeletal lesion, as compared with holding it with both hands [34].

Regarding of the implication of this study, the findings reveal an important information of an association between intensive smartphone use and the occurrence of neck disorders. Additionally, the information may be used to develop prevention measure and health promotion initiatives that aim to decrease neck flexion and smoking to address the risk of neck disorders associated with smartphone users.

The current study has some limitations. A general limitation of cross-sectional studies is that they do not show cause and effect [35]; however, this method was useful as a starting point to gauge smartphone use and associated symptoms in the university student population. Our study also did not examine some characteristics of daily smartphone use reported in other studies (e.g. number of text messages and neck postures). Furthermore, as our sample consisted of only young people we cannot compare differences between younger and older age groups as previous studies have. Additionally, it should be noted that a self-administered questionnaire increases the risk of response bias [9]. In future studies we suggest participants should be included from beyond the university student sector, and a cohort with more smoking smartphone users should be studied to confirm our finding of smoking as an associated factor.

5 Conclusion

Individual factor of smoking and ergonomic factor of the neck flexion posture were both associated with the occurrence of neck musculoskeletal disorders in smartphone users in the present study. To the best of our knowledge, this is the first study which has demonstrated that neck disorders in smartphone users are associated with neck flexion postures and smoking. The current data suggests that neck disorders in smartphone users can be reduced through measures that aim to decrease neck flexion and smoking.

Conflict of interest

None to report.