The association between mobile phone use and neuromusculoskeletal complaints

2.1 Research sample and inclusion criteria

The total population of the university is 4691 students (4240 undergraduate students, 451 postgraduate students, 1,815 females, 2906 males) and around 3600 students were available on campus. The questionnaire was designed using Google Forms and distributed among 720 students by email using systematic sampling. The students email list arranged alphabetically was acquired and the questionnaire was sent randomly to each fifth student in the list. A reminder was sent once again after two weeks. A total of 228 undergraduate university students responded and filled the questionnaire (response rate 31.7%).

The inclusion criteria included adequate questionnaire completion by young adults aged 18 to 32 years with no known musculoskeletal disorders or upper extremity pains due to any genetic or traumatic disorders or infections. Two subjects were excluded because they did not match the inclusion criteria and the final sample consisted of 226 subjects (age = 20.7±1.27 years, females (n = 103, age = 20.5 (±1.32) years), males (n = 123, age = 20.8 (±1.22) years).

2.2 Questionnaire

A structured and adapted questionnaire was used to collect data on sociodemographic variables (age, gender, height, and weight), awareness of the effect of prolonged mobile phone use, mobile phone characteristics (model and size), usage habits (duration and hand/finger used for typing), and the presence and location of musculoskeletal pain (Appendix). The subjects were asked to measure the hand length, which is defined as the distance from the wrist to the tip of the middle finger. To avoid confusion and to have a standard hand length measurement, a guiding figure was used to indicate the required length clearly (question 4 in the Appendix) [15].

The questionnaire was structured by two biomedical engineering professors after the review of the relevant literature. Questions regarding the musculoskeletal complaints were constructed based on previous questionnaires in the literature [4, 17] and internal reliability test was done. Prior to data collection, a pilot study on 30 subjects was conducted to ensure the clarity of the questions, content, relevance, and time of completion. The questionnaire was handed to the 30 participants. During the filling time, the researchers were available to explain any unclear questions and taking comments. After completing the questionnaire, the participants were asked about any difficulty filling the questionnaire or any unclear parts/repeated questions. Accordingly, the questions were reviewed and refined after the pilot study. Following the pilot study, the questionnaire was developed and distributed via Google Forms.

For testing the internal consistency reliability, a Cronbach Alpha test was done on the first 30 filled questionnaire considering the questions about the musculoskeletal health and resulted in an acceptable inter consistency reliability (α= 0.75).

2.3 Data analysis

Questionnaire results were analysed using the statistical toolboxes within MATLAB software (R2020b). The frequencies of occurrence and percentages are given for categorical questions. The mean values and ranges are given for continuous measures. Statistical comparisons between values are provided where applicable using the two-tailed N-1 Chi-Square test for different groups, t-test or one-way ANOVA for three or more unmatched groups. A p-value of less than 0.05 was considered statistically significant.

Given the large variations in the hand sizes of the participants, a ratio of the length of the hand divided by the width of the mobile phone was used to correlate the relative size of the users’ hands to the presence of pain. Accordingly, the participants were divided into three groups. Those with hand-to-phone ratios of less than 2.3 are considered small (n = 75), those with ratios between 2.3 and 2.5 as average (n = 76), and those with ratios greater than 2.5 as large (n = 75).

3.1 Body mass index and mobile phone use

The average body mass index (BMI) for the sample was 23.8 (±4.24). The sample shows no statistically significant differences (one-way ANOVA, F-value = 1.95321, p = 0.121937) in the BMI between those spending a long time on their phones and those less addicted to mobile phones. Even though smartphone addiction and duration of use can have a negative impact on physical health by reducing daily physical activities [16, 18]. Similarly, other studies reported no relation between BMI and time spent using mobile phones or playing video games [17, 19].

3.2 Pain and mobile phone use duration

Generally, pain in the neck/upper back was the most frequently self-reported pain (59.7%, n = 135), followed by pain in the shoulders (33.6%, n = 76), and pain in the hands and wrist (27.9%, n = 63; 21.0%, n = 61, respectively). Similar results were reported in other studies [4, 21]. The frequent neck pain can be explained by the constantly flexed neck and arms with unsupported elbows during prolonged mobile phone use, which can cause excessive static load on the neck and shoulders [7, 22]. Studies on surface EMG showed an increased activation of the extensor muscles in the neck and thumb, which is correlated to pain in the neck, shoulders, and wrists [11, 23]. Moreover, Zirek et al. [7] have suggested that holding devices with one hand and controlling them using one finger may cause chronic pain in the neck and upper extremities.

To investigate the prolonged use of the mobile phone and musculoskeletal pain, the sample was divided into four groups based on the daily time spent using the mobile phone (Table 1). Those spending more time using their mobile phones reported more moderate to severe pain in comparison with the other groups. However, these differences are statistically significant only for pain in the neck/upper back (p = 0.03) as well as for pain in the hands (p = 0.043). These results agree with Regiani Bueno et al. [11], who reported that individuals using smartphones from 4-5 hours daily tended to have more severe pain symptoms than those with less than two hours of daily use. According to their results, the most affected areas were the neck (43.87%) followed by the hand/wrist (30.87%). Namwongsa et al. [21] reported that the neck is the most painful body region after using smartphones with flexed neck posture being an associated factor. Alsalameh et al. [20] reported a significant association between mobile phone addiction and neuromusculoskeletal problems in the neck (p = 0.041) and hand/wrist (p = 0.026). Similarly, Peak [24] found a significant correlation between smartphone addiction and pain in the neck and hands (p < 0.05). Continuously flexing the head forward or flexing the arms results in a posture that explains the pain in the neck, shoulders, and hands [11].

The percentage of those suffering from pain was higher for those with a smaller hand-to-phone ratio compared to the average and large hand-to-phone ratio (Table 2). This can be explained by extra stretching in the muscles of the fingers to reach the target on relatively large screens, which results in increased muscle activity and pain in the lower arm and hand muscles for prolonged mobile phone use. For example, the extensor pollicis longus muscle is strained more and has higher muscle activity while texting on large screen sizes compared to small screen sizes [25].

Despite the high pain percentages, the hand-to-phone ratio was a statistically significant factor only for pain in the neck/upper back (p = 0.026) and shoulders (p < 0.01), given the probability of pain increases for a small hand-to-phone ratio.

The use of the hand-to-phone ratio in investigating the relationship between hand size and the existence of pain can be an important tool to reduce the possible negative effect of user preference in selecting a mobile phone. Users tend to purchase trending mobile phones rather than those suitable for their hand size and usability [26, 27]. Kim and Kim [28] found no significant correlation between touch screen size and pain when they used the absolute screen size, even though a tendency for more comfort when using larger screens was reported.

A statistically significant relation of pain in the neck/upper back, shoulders, upper arms, and lower arms with gender was found (Table 3). Females suffer more from moderate to severe pain. Other studies have demonstrated similar results where the prevalence of neck/shoulder pain was significantly higher (p < 0.01) in females than in males [9, 29]. This can be related to muscular activity; females had higher muscle activity during entering SMS messages than males [22]. In this study, females’ average hand size was significantly smaller (p < 0.00001) than males (17.04 cm (±1.20), 18.60 cm (±1.28), respectively). This results in a larger range of motion of the thumb in females to reach the target on the screen. When the thumb and fingers and their associated joints are subjected to operational stresses exceeding their intended function, pain and musculoskeletal disorders can result [27, 30].

Out of the 226 subjects, 104 subjects (46.0%) used their right hand in texting, similarly 104 subjects (46.0%) used both hands, and only 18 subjects (8.0%) used their left hand. The thumb was the most often used finger in texting and scrolling by 187 subjects (82.7%) followed by both the thumb and index for 22 subjects (9.7%).

A significant relation was found between the hand/mobile ratio and the tendency to use one or two hands (p = 0.020806), given 58.7% of those with a small hand/mobile ratio used both hands while 41.3% used one hand. For those with a larger hand/mobile ratio, 42.7% used both hands and 57.3% used one hand. Previous research has shown that anthropometry and the design of mobile phones have an impact on the development of fatigue and discomfort in body parts such as the hands and shoulders [31]. Individuals who use smartphones with one hand perform repetitive wrist flexion/extension causing increased pressure in the carpal tunnel [32–35]. Thus, it would be more comfortable to hold the phone with both hands and distribute the required work on both hands’ muscles [25].

Similarly, a significant relation was found between hand/s used for texting and gender (p = 0.041641) with more females (53.4%) tending to use both hands for texting than males (39.8%). This might be related to the significantly smaller hand size of females (17.04 cm±1.20) compared to males (18.60 cm±1.28). Thus, females might tend to use two hands to make it easier for the thumb to reach the target on the screen in comparison with using one hand.

3.6 Symptoms of carpal and cubital tunnel syndromes

Repetitive hand and wrist use over a prolonged period results in aggravating the tendons in the wrist and increasing the pressure on the median nerve and ending up with carpal tunnel syndrome [36]. Nearly half of the sample (n = 114, 50.4%) had symptoms in one or more of their fingers. This high prevalence of symptoms necessitates highlighting the potential risks of prolonged mobile phone use on upper extremity health. To investigate the use of the mobile phone and the incidence of these symptoms of carpal and cubital tunnel syndromes, the subjects were divided into four groups, i.e., those with symptoms of carpal syndrome, with symptoms of cubital syndrome, with symptoms of both syndromes, and no symptoms.

The symptoms of cubital tunnel syndrome frequency of occurrence were significantly higher (p = 0.010476) among those spending more than 6 hours using their mobile phones daily (26.0%) in comparison with the less than 2 hours, 2-4 hours, and 4-6 hours groups (12.5%, 5.6%, and 11.2%, respectively) (Table 4). No significant differences were recorded for the frequency of occurrence of the symptoms of carpal tunnel syndrome or both syndromes. The incidence of symptoms of carpal tunnel syndrome was very high for all mobile phone usage time groups. This high rate is consistent with many studies that have shown the excessive of electronic devices can harm affect the transverse carpal ligament and the median nerve, resulting in pain, tingling, and numbness in the hands [34]. Non-neutral wrists can cause carpal tunnel syndrome by increasing pressure in the tunnel [32, 33]. The frequency, duration, and years of using electronic devices may cause enlargement of the median nerve within the carpal tunnel [35, 37].

As shown in Table 5, males tend to have significantly fewer symptoms of syndromes in their fingers (43.9%) than females (63.1%) with p = 0.003979. This was driven by a significantly higher incidence of symptoms of carpal syndrome within females (33.0%) compared to males (21.1%) with p = 0.044135. Al Shahrani et al. [38] reported that symptoms of carpal tunnel syndrome were significantly higher in females compared to males (p = 0.001). The repeated wrist and finger motions during prolonged mobile phone use are associated with an increased range of motion for females’ small hands compared to males and this increases the pressure on the median nerve that may end up with carpal tunnel syndrome.

The location of the pain on the right, left, or both upper extremities is investigated and compared to the used hand. Out of the 117 subjects suffering from pain, 20 subjects (17.1%) have pain on the extremity opposite to the one used for texting, 64 subjects (54.7%) have pain on the same extremity/ies used for texting, and 33 subjects (28.2%) use both hands to text while having pain on just one side.

In one-handed use, the mobile phone is carried in the hand and the thumb of the same hand is used for texting. This requires the thumb to extend and move in a larger range of motion to reach the target compared to two-handed use, particularly in large size phones. Additionally, the repetitive flexion/extension of the wrist in one-handed mobile phone use leads to narrowing and increasing the pressure in the carpal tunnel instead of distributing the work/stress on both hands [25, 40]. Previous studies have reported higher muscle activity of the Upper Trapezius (UT), Extensor Pollicis Longus (EPL), Extensor Carpi Radialis (ECR), and Abductor Pollicis (AP) during one-handed smartphone use compared to two-handed smartphone use [41, 42]. Because of microscopic damage to the blood vessels, muscles, and nerves during task performance, continuous muscle contraction in one-handed use may lead to increased risk to musculoskeletal disorders [12]. As a result, using a smartphone with both hands is advised to reduce the musculoskeletal problems [41].

3.8 Awareness of the risks of prolonged mobile phone use

The participants were asked about their knowledge of the impact of mobile phone use on the health of the upper extremity (Fig. 1). Around 75% of the participants (n = 170) declared that they had already heard or read something about the effect of prolonged use of mobile phones on health. The participants’ sources of information varied, with the media being the most reported source (n = 104, 46.0%), while mobile phone disclaimers/warnings were the source of information for only 4 subjects (1.8%). The warning about the potential negative effects of prolonged mobile phone use on health is hidden in user manuals, which most users do not read.

OPEN IN VIEWER

Fig. 1

Sources of information about the potential effect of prolonged mobile phone use.

Out of the 170 subjects already aware of the possible risks of prolonged use of mobile phones, 130 subjects (76.5%) declared that they take breaks while texting or they plan to do that in the future. Within the 57 participants with no previous awareness of the risks of prolonged mobile phone use, only 32 subjects (57.1%) expressed that they take breaks or will do in the future. This statistically significant difference (p < 0.05) indicates that good knowledge and a clear warning can help protect young adults from the risks of mobile phones. Thus, policymakers and regulatory agencies should compel mobile phone manufacturers to include a clear disclaimer or label on their products that helps choosing appropriate mobile phones and developing better usage habits.