Prevalence of musculoskeletal pain among professional drivers: A systematic review

Abstract Objectives Professional drivers are at high risk of developing musculoskeletal pain (MSP) due to risk factors such as prolonged sitting, whole body vibration, awkward posture, and repetitive actions. This review investigates the reported prevalence of MSP among professional drivers. Methods An electronic search of Medline (1946 + via OvidSP), Embase (1974 + OvidSP), CINAHL (1982+), AMED, PubMed, and Web of Science from 1990 to July 2019 was performed. Methodological quality of studies was assessed using three quality assessment tools for cross‐sectional, case‐control, and prospective cohort studies. The prevalence of MSP was reported using descriptive analysis. Results A total of 56 studies conducted in 23 different countries across a total of 14 types of occupational transport were reviewed. Data of a total pooled population of 18 882 professional drivers were analyzed for MSP. The prevalence of MSP ranged between 43.1% and 93%. The low back was the most frequently reported body region for MSP with a meta‐prevalence rate of 53% (N = 9998). Neck, shoulder, and upper back were the other common regions with high prevalence. Conclusion There is a high prevalence of MSP in professional drivers and low back was the most frequently reported body region, followed by neck, upper back, shoulder, knee, hip/thigh, wrist, ankle, and elbow. MSP is complicated in nature and therefore in‐depth exploration of causal relationships between MSP and risk factors is necessary so that appropriate healthcare programs can be initiated to prevent and treat MSP effectively.

can trigger disability, leading to reduced work capability and lost wages. 4 In addition to work absenteeism, WRMSDs lead to considerable healthcare costs and economic loss to society at all levels. 5,6 In 2018/2019, the UK Health and Safety Executive (HSE) reported that the prevalence of WRMSDs was 498 000 out of a total of 1 354 000 for all work-related illnesses, with a 37% prevalence and accounting for 29% of all working days lost due to work-related ill health. 7 Recent findings published by the US Bureau of Labor Statistics in 2017 indicated that bus drivers are one of the top three occupations with the highest rates of musculoskeletal disorders, apart from emergency responders and nurses. 8 Specifically, transit and intercity bus drivers had the highest incidence rates (206 per 10 000 full-time workers) of musculoskeletal disorders in 2017. 8 WRMSDs are painful disorders of muscles, bones, nerves, tendons, and other soft tissues, due to workplace activity. 3,9 This review examined the prevalence of self-reported MSP as a marker of WRMSDs among professional drivers.
Professional drivers are defined as those people whose key task is to operate a motor vehicle as their main occupational activity. 9 Previous research has reported high prevalence of MSP in bus drivers (80%), 10 truck drivers (81%), 11 and taxi drivers (71%), 1 with low back pain (LBP) being one of the most commonly reported MSPs. [12][13][14] Other types of MSP such as shoulder and knee pain are also reported among the professional driving populations. 15,16 Investigations into the different types of MSP among professional drivers are sparse and the aim of this systematic review is to investigate the current research into the prevalence of different MSPs among professional drivers.
Due to the high prevalence, negative health consequences, and economic impact, MSP is a major occupational health concern for professional drivers. To the researchers' knowledge, no review has evaluated and reported systematically on the prevalence of MSP among this group of professionals. The current systematic review aims to answer two research questions: (a) What is the estimated prevalence of MSP among professional drivers? (b) What is the prevalence of MSP among drivers who drive light-to-moderate and heavy vehicles? The findings of the current review may generate new scientific evidence about the magnitude of MSP among professional drivers. Evidence generated from this may be useful to policy makers, healthcare providers, researchers, and ergonomists to identify occupational risks of professional driving and design appropriate assessment and interventions to reduce rates of MSP among professional drivers. A better understanding of the prevalence of MSP and its risk factors among professional drivers may be beneficial to establish professional guidelines for primary prevention, identify potential work modifications for secondary prevention and provide evidence-based guidelines to those involved in the decision-making process of MSP claims associated with professional driving.

| MATERIALS AND METHODS
This systematic review had been conducted and reported according to the guidelines of the Preferred Reporting Items for Systematic Review and Meta-Analysis Protocols (PRISMA-P). 17

| Literature search
An electronic search of Medline (1946 + via OvidSP), Embase (1974 + OvidSP), CINAHL (1982+), AMED, PubMed, and Web of Science was undertaken using a broad strategy. A combination of three main components: professional driving, musculoskeletal disorder, and prevalence/ risk were used as MeSH and/or text word search terms. The terms within each component were linked with "OR," and the three groups were linked with "AND." A full search strategy based on the Embase literature database is shown in Appendix A. Similar strategies were performed using other databases.
Studies that did not meet the eligibility criteria for this review were excluded through screening titles, abstracts and full texts. Reference lists of included studies were also searched for additional relevant studies. A gray literature search was conducted using the following sources of information: Open Grey, The King's Fund, and WHO (World Health Organization).

| Eligibility criteria
The criteria required for inclusion in the review were studies that (a) included professional drivers of >18 years old with at least 1 year of professional driving experience; (b) included professional drivers, defined as those whose main task was to operate a motor vehicle in traffic conditions; (c) had a primary purpose of examining the prevalence of MSP among professional drivers; (d) were published in peer-reviewed English language journals; (e) utilized cross-sectional, case-control, or prospective cohort study designs and reported prevalence of MSP; and (f) reported results on prevalence for MSP along with risk factors associated with professional driving.
Studies that were excluded (a) had no specific population (eg, too broad); (b) reported incidence of MSP without prevalence; and (d) were non-scientific studies (eg, editorials, commentaries), literature reviews, reporting only treatment of pain, basic sciences, or cadaver studies.

| Screening process
Search results were exported into Endnote™ (EndNote x8 for Windows version) to check for duplicate studies which were removed accordingly. Bibliographic records were then exported from Endnote™ into Microsoft Excel to enable further manual deletion of duplications. Initial screening was conducted on the title and abstract of studies by one reviewer and cross-checked by a second reviewer. The second level screening evaluated full-text reports for studies deemed potentially eligible after the first screening. Disagreements among reviewers were resolved by discussion and reflection with the third reviewer.

| Methodological quality assessment
The methodological quality of studies was assessed independently by two reviewers using three quality assessment tools. A risk of bias tool was used to assess the quality of cross-sectional studies. 18 This tool assesses external validity through four items (1)(2)(3)(4), and evaluates internal validity using six items (5-10). Case-control and prospective cohort studies were assessed using the Newcastle-Ottawa Scale for observational studies. 19 A case-control version of the Newcastle-Ottawa Scale was used for case-control studies consisting of nine items assessing selection, comparability and exposure. The Newcastle-Ottawa Scale for cohort studies was used for prospective cohort studies that assessed nine items of selection, comparability, and outcome.
The overall methodological quality of each included study was rated as being high quality (low risk of bias), medium quality (high risk of bias), or low quality (very high risk of bias). Total scores from the risk of bias tool and Newcastle-Ottawa scales were categorized into three groups: Very high risk of bias (0-4 points), high risk of bias (5-6 points), and low risk of bias (7+ points). 20 This method is consistent with Grades of Recommendation, Assessment, Development and Evaluation and Cochrane approaches. 21

| Data extraction
The study characteristics extracted from the reviewed studies included information on the authors, year of publication, country, study design, number of participants, type of vehicle driven, and aim of study. If reported, further information regarding participants' mean age was collected. For information regarding the prevalence of MSP, the type of professional driving (vehicle driven), type/area of MSP, prevalence duration, and results of prevalence were collected. If the case-control and prospective cohort studies provided a baseline cross-sectional prevalence rate of MSP among the drivers, the reported prevalence rate was extracted for this review.

| Analysis of data
The prevalence of MSP presented among the different studies was reported using descriptive analysis. The metaprevalence estimate of MSP for each specific body region reported for professional drivers was calculated by weighing the studies according to their sample size within pooled samples. This was done using the meta-prevalence estimate formula in Microsoft Excel; thus, giving a meta-prevalence estimate of MSP for each body region. 22 Where available, prevalence rates from the median prevalence duration were used for calculation. In this review, the most commonly reported prevalence duration was 12 months. For this reason, if data for 12-month prevalence were available, they were used to calculate the estimated meta-prevalence. In addition, subgroup descriptive analysis was conducted to calculate the meta-prevalence estimate of MSP among professional drivers in two subgroups, namely low-moderate vehicles and heavy vehicles. For subgroup analysis, buses, trucks, and cranes were classified as heavy vehicles while all other types of vehicles were classified as low-moderate vehicles.

| Study selection
The search strategy yielded a total of 1028 citations, 242 of which were deemed potentially relevant at the first cycle of screening. On further review, 56 studies satisfied the eligibility criteria. The PRISMA flowchart explaining the process of selection is shown in Figure 1

| Study characteristics
The 56 studies involved a total of 18 882 participants, included in 48 cross-sectional studies, five prospective cohort studies, and three case-control studies. The characteristics of the studies included are summarized in Table 1. The age of participants ranged from 20 to 71 years with a mean age of 42.8 years. Of those studies reporting mean years of driving experience and mean hours driving per day, results showed 13.1 years and 9.6 hours, respectively. The included studies were conducted in 23 different countries, nine in the United Kingdom, eight in the USA, and seven in Italy. Studies from other countries included the Netherlands (four) and India (four), Malaysia (three) and Iran (three), Israel, Ghana, Nigeria, Taiwan, China, Canada, and Japan (two each), and one study each from Brazil, Sweden, Finland, Poland, Norway, South Africa, Germany, Turkey, and Hong Kong. A total of 14 types of occupational transport were represented by these studies, most commonly buses in 18 studies, trucks in 11 studies, and taxis in 10 studies. Other vehicles included transit vehicles, minibuses, tractors, straddle carriers, police cars, rally cars, delivery vans, cars, garbage trucks, earth moving vehicles, cranes, and forklifts.

| Quality of reviewed articles
Of the 56 studies included in the study, seven were considered of low methodological quality with a very high risk of bias, 32 of medium methodological quality with a high risk of bias, and 17 studies were considered of high methodological quality with a low risk of bias. Selection bias was apparent in most of the cross-sectional studies ( Table 2, items 1 and 2) and many of them failed to provide an acceptable case definition (Table 2, item 6). Additionally, many prospective cohort studies presented the outcome of interest at the start of the study (Table 3A,B).

| Prevalence of musculoskeletal pain among professional drivers
All studies included investigated prevalence rates of musculoskeletal pain (MSP) among professional drivers (Table 4).
Of these 56 studies, 18 studies (N = 6588) reported total prevalence rates of MSP ranging between 43.1% and 93%, with a mean of 73%. The low back region was the most frequently reported body region, with 43 studies (N = 9998) reporting a prevalence rate of LBP between 17% and 82.9%, with a metaprevalence rate of 53%. Twenty-six studies (N = 3480) reported prevalence of neck pain between 7.1% and 78.8% with a meta-prevalence rate of 42.4%. Shoulder pain was reported between 6.3% and 79.4% in 19 studies (N = 2751) with a meta-prevalence of 39.2%. Fourteen studies (N = 1299) reported prevalence of upper back pain between 2.6% and 60.3% with an estimated meta-prevalence rate of 25.5% and 16 studies (N = 1460) reported knee pain prevalence between 5.6% and 36% with an estimated meta-prevalence of 21.8%. Hip/thigh pain was reported with a prevalence between 2.7% and 22.2% with a meta-prevalence of 19.5% in eight studies (N = 655). Wrist pain prevalence ranged between 1.3% and 31% in nine studies (N = 239), reporting an estimated meta-prevalence of 11.5%. The other body regions affected were ankle (N = 266) and elbow (N = 313) and these studies reported an estimated meta-prevalence of 15.1% and 7.9%, respectively.
A summary of the overall breakdown of meta-prevalence rates for specific body regions among professional drivers is presented in Figure 2. The results of the sub analysis of MSPs reported about professional drivers who drive light-moderate vehicles and heavy vehicles are presented in Figure 3A,B.

| Prevalence of MSP among professional drivers
The purpose of this review was to investigate the prevalence of MSP among professional drivers. An international expert group on WRMSDs initiated the current systematic review to identify the magnitude and possible variability of MSP among professional drivers globally. In the absence of comprehensive evidence on MSP among professional drivers, it is difficult to coordinate and provide appropriate services for the management of MSP in this group. The findings of this review provides comprehensive, comparable data on the prevalence of MSP among professional drivers. 8 These findings can support policies and practices of policy makers and occupational health authorities, such as the HSE in the United Kingdom, and similar bodies in other countries to understand and address MSP among professional drivers, leading to improvement in the health of this working population.
The authors of this review consider this to be the first systematic review of epidemiological literature investigating the prevalence of MSP among this group of professionals. Heterogeneity was noted in the scope of reported prevalence, ranging from point prevalence to lifetime prevalence ( Table 4). The most widely applied approach for estimating prevalence among professional drivers was 12-month prevalence ranging from 43.1% to 93%. Within self-reported epidemiological studies, longer prevalence periods increase the likelihood of participants being unreliable in recalling experiences of MSP. 18 It is suggested that in order to reduce risk of bias, reporting 12-month prevalence is an adequate period and can help establish standard reporting procedures, making the data comparable globally with a greater precision of prevalence. Many cross-sectional and case-control studies included in this review reported that professional drivers had higher MSP prevalence than non-professional driver controls. 1 Boshuizen et al (1992) 48 Bovenzi and Betta (1994) 51 Bovenzi and Zadini (1992) 23 Gangopadhyay and Dev (2012) 58 High Gyi and Porter (1998) Raanaas and Anderson (2008) 76 Robb and Mansfield (2007)    Anderson Bovenzi

) High
Note: High, high quality (low risk of bias); Low, low quality (high risk of bias); Med, medium quality (moderate risk of bias); N, no; Y, yes; 1-Representativeness of the exposed cohort. 2-Selection of the nonexposed cohort. 3-Ascertainment of exposure. 4-Demonstration that outcome of interest was not present at the start of study. 5-Study controls for important factor. 6-Study controls for an additional factor. 7-Assessment of outcome. 8-Was follow-up long enough for outcomes to occur? 9-Adequacy of follow-up cohorts. had not been conducted so far in the field of musculoskeletal disorders related to work.

| Prevalence of LBP
Previous research indicates that low back, neck and shoulder regions are the most commonly reported body regions affected by MSP. 24 The present review found that the low back was the most commonly affected region, followed by neck and shoulder. The review findings suggest that professional drivers have a higher prevalence rate for LBP (53%) when compared with other occupations such as manual material handling workers (25%) and physiotherapists (50%). 25,26 When compared to the prevalence rates (38%) reported globally for LBP, 27 the higher rate observed among professional drivers indicates the significance of the problem for this occupational group. Findings in this review are complemented by a recent smaller review reporting a high prevalence of LBP and neck pain among bus drivers. 28 With a much larger pooled sample (N = 18 882), the current review reports a meta-prevalence of LBP (53%), consistent with the high prevalence of LBP reported in other recent professional driving studies 29-31 at 61.7%, 49%, and 54% respectively. Another systematic review of the global prevalence of LBP reported a mean 12-month prevalence of 38.9%. 32 This suggests the increased risk of occupational groups, such as professional drivers, developing low back symptoms and disorders. The findings from the current review subgroup analysis ( Figure 3A,B) showed a similar trend in the prevalence of LBP in drivers of both low-moderate vehicles and heavy vehicles.
The high prevalence of LBP is considered to place great financial burden on, and possibly contribute to early retirement, among such individuals. 32,33 The findings on LBP from this review would support action by the relevant transport-occupational health sectors toward the prevention and management of LBP among such drivers. It is suggested that the current review findings might prompt practitioners and policy makers across different countries to understand and act appropriately to improve overall health care and wellbeing of professional drivers.

| Prevalence of MSP in the upper body region
The 12-month reported prevalence of neck pain ranged between 7.1% and 78.8%. A previous synthesis of 249 papers reported a 12-month prevalence of neck pain similarly ranging between 12.1% and 71.5% in the general population, 34 with most estimates ranging between 30% and 50%. Our estimated metaprevalence of 42.4% is comparable to a 12-month global mean prevalence of 37.2%. 35 This seems to indicate that professional drivers are at a higher risk of developing neck pain than the general public. The large variations of prevalence estimates in the general population have been credited to differences in the demographic and socio-economic status of the surveyed populations, methods of case definition, and ascertainment and the criteria for inclusion/exclusion in various studies. 34 these variables could also contribute to the large variations of prevalence estimates presented in this review.
In the present review, the meta-prevalence of MSP in the neck, shoulder, and upper back region was 42.4%, 39.2%, and 25.5% respectively. The prevalence of shoulder pain among drivers is higher than the global 12-month prevalence of shoulder pain in the general public (36.7%). 37 Although three included studies reported higher prevalence of MSP in the upper back than the shoulder region, 2,9,38 the meta-prevalence of MSP as indicated in Figure 2 suggests that the shoulder region is more affected than the upper back. It is noteworthy that the subgroup analysis from Figure 3A,B indicated prevalence of MSP in the neck and shoulder regions as noticeably higher among drivers in the light-moderate vehicles sector compared to drivers using heavy vehicles. Involvement of neck, shoulder, and upper back pain has been well documented among professional bus driver 15 and significant prevalence of this body region reported among professional drivers in general, demonstrates a clinical need to investigate the biomechanics of the upper quadrant region among this group. Currently, there is a paucity of evidence available for practitioners to understand the pathogenesis of upper quadrant musculoskeletal problems among professional drivers. It is suggested that future research on the kinetics and kinematic parameters of scapula kinesis and their association with musculoskeletal symptoms is warranted. Furthermore, available scientific evidence on drivers who experience neck pain, also shows a higher prevalence of upper back and shoulder pain compared to drivers without neck pain, 15 and this warrants investigation of the upper quadrant motor control mechanisms among professional drivers.

| Prevalence of MSP in the lower extremity region
This review reported an estimated meta-prevalence of 21.8% knee pain and 19.5% hip pain, demonstrating that MSPs are common in lower extremity regions among professional drivers. The prevalence of MSPs in the lower extremity regions were generally higher among heavy vehicle drivers compared to those driving low-moderate vehicles. As shown in Figure 3B, the ankle was the least affected region in the lower extremity with a meta-prevalence rate of 10.5% and 16.4% among drivers driving low-moderate and heavy vehicles, respectively. Some of the MSP experienced in the upper and lower extremities might possibly be referred pain from the spine, or have local origin due to mechanical loading of these joints associated with postures and repetitive movements involved in professional driving. 14 Generally, the studies included in this review did not clarify the spinal origin of pain in the extremities and hence, no conclusions can be drawn for the spinal contribution of MSP to pain in extremities related to professional driving.

| Implications for practice
The findings of this review provide scientific evidence internationally to stake holders such as policy makers, insurance providers, occupational health authorities, researchers, and clinicians on the magnitude of MSP among professional drivers. Aside from providing scientific evidence on MSP to those concerned, the review findings raise several other key points for consideration. First, the availability of prevalence data alone may not be helpful in planning health interventions or policies, but the review findings point to a need to investigate risk factors that contribute to MSP among professional drivers so that adequate interventions could be designed to address this global issue. Further investigation of the multifaceted and complex risk factors and contributors to MSP is needed before work-place interventions can be attempted. Therefore, a systematic review to investigate risk factors and their causal relationship with MSP is urgently needed to assist policy makers in identifying and handling risk factors appropriately. Second, the biopsychosocial model needs to be considered when investigating management strategies for MSP in drivers. 39 Drivers' perceptions and experiences of MSP, including pain and other symptoms have not been studied and therefore need to be explored further to fully understand the phenomenon. Additionally, drivers' perceptions of health and wellbeing, work/life balance, and mental attitude might all contribute to MSP outcomes and further study could assist policy makers and health authorities to understand the needs and expectations of drivers with MSP. The professional drivers themselves should be involved in framing management strategies to combat MSP.

| Study limitations
The review highlighted some limitations. The use of the term "work related musculoskeletal disorders" was not consistent between the studies included. Often interchangeable terms such as: work-related musculoskeletal symptoms, musculoskeletal complaints, musculoskeletal problems, MSP, and musculoskeletal discomfort were used across studies. Nevertheless, the studies reported widely the presence of pain as one of the commonest presentations among participants. Thus, MSP was considered as an umbrella term and a main outcome of interest for the current review. However, it is possible, that some studies included cases of non-specific MSP that were not definitively linked to work. The absence of standardized methods across the studies and lack of general consensus to distinguish non-occupational MSP indicates the challenge in estimating prevalence of MSP among drivers.
It is possible that other tasks, in addition to driving, (eg, loading and unloading trucks) may have occurred in the different groups of professional drivers. However, neither the current review nor the studies which reported MSP among drivers accounted for any procedures to address this confounding factor. Because of the limitations discussed above, the reviewers urge some caution in interpreting the prevalence of MSP among professional drivers.

| CONCLUSION
The findings from the review provide evidence on the prevalence and severity of MSP among professional drivers. A wide range of prevalence rates of MSP affecting different body regions have been reported, with the highest prevalence found in the low back region, followed by the neck, shoulder and upper back regions. The review findings suggest that further investigation into the multiplicity of risk factors for MSP is necessary so that policy makers, health professionals, drivers themselves, and other stake holders can work together toward combatting MSP among this population.