Work-related back discomfort and associated factors among automotive maintenance mechanics in Eastern Nigeria: A cross sectional study

Abstract

BACKGROUND:

Back pain has been identified as a common cause of disability in the working population. Automotive mechanics habitually use awkward back posture in their course of manual activity and hence may be at risk of work-related back pain.

OBJECTIVE:

To investigate the prevalence, pattern and severity of back pain among automotive maintenance mechanics, as well as the personal and job variables associated with or predicting occurrence of back pain.

METHOD:

Using a cross-sectional design, information about self-reported back pain and the associated variables were collected among 684 randomly recruited automotive mechanics.

RESULT:

Prevalence of back pain was 76.02%; with the majority experiencing low back pain. 63.3% of the workers reported they limited their activity due to the back pain. Older workers (>50 years), daily work lasting ≥5 hours duration, no more than primary education, being normal weight, frequent use of kneeling and sustained postures, and lack of knowledge of ergonomic postures were associated with increased prevalence of back pain. Lack of job autonomy, inadequate task clarity, heavy physical work load, manual material handling, strenuous posture, noisy environment, vibrations, work schedule and inadequate auxiliary support were also associated with increased prevalence of back pain among the mechanics.

CONCLUSION:

Work-related back pain is prevalent among automotive maintenance mechanics. Work-related back pain is high among automotive maintenance mechanics. Workstation policy and legislation on reduction of risks with combined health literacy and ergonomic education programs in this occupational group are imperative.

Keywords

Musculoskeletal risk back pain manual handling automobile servicing and repair

1 Background of the study

Back pain is a common cause of disability in the working population [1 –3], and its total costs have been estimated to be among the highest for disease for which economic analysis is available [4]. Associations between working environment and musculoskeletal symptoms (MSS), including back pain, have been reported, and ergonomic factors such as awkward working postures, static load and task invariability are among the most important risk factors for MSS [5, 6]. Occupations involving manual handling and physical workload are known to predispose to musculoskeletal disorders, including low back pain [7].

Automotive maintenance mechanics mostly work standing, kneeling or half kneeling, in forward flexion, and on a hard floor. Individuals who continuously adopt these working positions are more likely to suffer from back pain [8]. European and Asian studies have reported that this group of workers suffers from various work-related health complaints, including back pain [8, 9], with higher reported prevalence compared to workers in other occupations [9 –11]. The prevalence of work-related MSS, including back pain, may be even higher in developing countries like Nigeria, due to the absence of effective work injury prevention programs [12, 13].

This is so given that similar manual handling occupational groups in Nigeria have reported higher prevalence of musculoskeletal disorders compared to developed countries [14 –17] indicating that Nigeria workers maybe at higher risk to work-related musculoskeletal disorders. In order to effect ergonomic interventions among this group either by industry or government policies, epidemiological investigation into the level prevalence and risk exposure would be the first step. No study has investigated the prevalence of back pain among automotive maintenance mechanics in Nigeria. Also there is no literature on the specific correlates, determinants or predictors of back pain in this group among African populations. This study therefore aimed to investigate the prevalence, pattern and severity of self-reported back pain and associated personal and job-related characteristics; and to predict occurrence of back pain among this group of workers.

2 Materials and methods

This study is focused on automotive maintenance mechanics in Enugu and Nsukka metropolises ofEnugu State, Eastern Nigeria who have in the past 12 months worked in direct mechanic activity. Enugu is the capital of the Enugu state Nigeria and according to the 2006 Nigerian census the Enugu metropolitan area has an estimated population of 722,664. Nsukka is a town and Local Government Area in Enugu South-East Nigeria. Nsukka LGA has an area of 1,810 km² and a population of 309,633 at the 2006 census [18].

2.1 Method

The study employed a cross-sectional descriptive design, with 684 participants between May and August 2013. A multi-stage sampling technique was used. First, a list of all local government areas in Enugu and Nsukka metropolises was compiled (n = 5). This was followed by a list of every layout in each of the local governments, yielding a total of 87 layouts (10, 12, 14, 16, 18, 10 in A, B, C, D and E local government areas). Altogether, a total of 64 maintenance sites were identified each having between 3 and 26 mechanics, giving a total of 1048. Physical examination and subjective assessment of the workers, as well as discussions with the mechanic workers, were done in order to rule out those who did not meet the inclusion criteria into the study. Exclusion criteria were congenital spinal problems, spinal deformity or previous spinal surgery, lower limb length discrepancy or any foot deformity that could impact on back function. Sixteen people were ineligible for participation in the study due to evidence suggestive of scoliosis; 102 were excluded because they have back pain dating before commencing mechanic work or that their back pain were traceable to specific incidence of trauma outside their work. Another 7 were excluded because of limb length discrepancy. A further 117 mechanics refused to participate; the reason cited being mostly ‘not feeling like it’.

A list of eligible automotive mechanics was made for each of the sites, giving a total of 806. We aimed to sample at least half of the mechanics with a near to equal representation, according to the number of mechanics in each work station. We also aimed for a fair representation of urban and semi-urban situated stations. A proportional sampling was used to allocate the number of mechanics to be included from each site, layout and local area, according to the population of mechanics who met the eligibility criteria described.

2.2 Participants

A total of 693 automotive mechanics between the ages of 15 and 64 years, drawn from 64 workstations in Enugu and Nsukka metropolis, Nigeria and who met the inclusion criteria, participated in the study. Nine eligible mechanics were excluded because the forms on which measurements were written were not filled in completely. Therefore, data for 684 participants are reported. Ethical approval was obtained from the University of Nigeria Teaching Hospital Ethics and Research Committee. Participants were fully informed about the data collection procedures and protocol, after which informed consent was obtained from those who volunteered to participate. Only those who volunteered to participate in the study were recruited. To be included, an individual had to be an automotive mechanic, have worked consistently for at least one year before the start of the study, comprehend written English or Igbo language, and not have any musculoskeletal symptoms (defined as ache, pain, discomfort) of the back region not related to work exposure. Worker were excluded if the responded that their back problem had stated before they commenced automotive work or if their problem is traceable to traumatic events outside auto mechanic duty. Mechanics with congenital spinal deformities were also excluded.

2.3 Measurement

2.3.1 Background and demographics

A series of background and demographic items including age, marital status, highest education attainment, work experience, hours of mechanic activities per day were evaluated using a questionnaire.

2.3.2 Exposure assessment

Work exposure assessment (e.g. job characteristics, physical and psychosocial stresses of works, constraints of workplace and tools, and hazards of physical environment) was carried out using the Nag’s multi-method ergonomic checklist [19] as described by Vyas et al. [20]. This multi-method check list is a 25 item check list and sought responses to information such as job characteristics, physical and psychosocial stresses of work, constraints of workplace and tools, and hazards of physical environment. Following the methodology earlier described by Vyas et al. [20], workers were asked for their responses about their perception of the work aspect to be strenuous. Responses were given on a single digit score, on five point likertscale, from strong disagreement (1) to strong agreement (5), where lowest score indicated that a worker perceived the absence of a problem. The relative loading of scores for each section of the checkpoints was arrived at from the ratio of the summated score value for thatsection to that of maximum cumulative scores possible under that section in line with earlier literature [20]. Accordingly, relative loading of scores for each section were such that values greater than 0.5 was considered as a stressor. A reliability coefficient of 0.84 has been reported for the ergonomics checklists [20].

2.3.3 Outcome variables

Outcomes were back pain at any region of the back, knowledge of ergonomics, personal and work characteristics, and stressors. Back pain outcomes were assessed with a series of questions adapted from modified Nordic Musculoskeletal Questionnaire (NMQ) [21]. Apart from questions about back pain, the modified NMQ questioned further on the exact location of the back pain (i.e. upper, mid or lower back). We further modified the Nordic questionnaire to assess severity of pain. Both the English and Igbo language versions of the NMQ were available. The Igbo version was administered only to those who did not comprehend written English. Cross-cultural translation, validation and reliability of the Igbo language version have been reported elsewhere [14]. The primary outcome variable was the1-year prevalence of back pain (BP). A complaint of back pain was established with the question “Have you had any pain at the back during the past 12 months that you believe to be related to your work?”

2.4 Data analysis

An analysis was carried out to determine the minimum sample needed for the study, using the prevalence of back pain reported by Vyas et al. [20] and based on the minimum sample calculation for infinite population [22], a 95% level of confidence and a precision of 5% [22, 23]. Based on this analysis, a minimum sample of 619.6 participants was required. Data analysis was performed using Statistical Package for Social Sciences version 15 (SPSS Inc., Chicago, IL, USA). Descriptive statistics of frequency were used to analyze the report of demographics, anthropometric and job history data, as well as prevalence of back pain, knowledge of ergonomics and pattern, and severity of pain. Association of personal and job characteristics with back pain prevalence were assessed by Chi-square, and Tukey Post Hoc was used to delineate the specific point of differences in prevalence among the multinomial variables that showed significant association. Kolmogorov-Smirnov Test with Lilliefor’s correction was used for normality checks, and distribution of the data for most variables was found to be normal (p > 0.05). To understand the effects of work stressors on the prevalence of back pain, we used a multivariate analysis using binary logistic regression model with backward elimination method. In the regression model, variables such as specific perceived work factors were fed as continuous variables (0. 1), whereas personal and job characteristics variables that showed association with prevalence were applied as categorical covariates; such factors included age ≥30 years or <60 years, working experience <10 years, working for ≥5 hours per day, formal education ≤ primary school, and having no knowledge of ergonomic posture. All the variables were applied simultaneously in a backward logistic regression model, to derive the effect of each work stressor on the prevalence of back pain.

3 Result

3.1 Personal and job characteristics of participants

A total of 684 automotive maintenance mechanics aged 15–64 in Enugu state Eastern Nigeria participated in the study. Table 1 shows the personal characteristics of the participants. All the maintenance mechanics were males and most were about middle age, single, with primary education or less and of normal weight. Daily working hours were predominantly 5–7 hours, with most of the mechanics having 20 years or less of work experience in automotive maintenance. Tasks performed by the mechanics ranged from vulcanizing, wheel alignment, welding and cleaning to repair and servicing, and the main work postures adopted were squatting, standing and sustained postures.

3.2 Report of back pain

The prevalence, severity and pattern of distribution of back pain, as well as activity limitation by back pain, are shown in Table 2. A total of 76.02% (520) mechanics reported had at least one episode of back pain in the last 12 months, most of whom experienced the pain in the low back. About half of participants had been prevented from doing activity by back pain in the last 12 months. Fewer than one in five responded that they had knowledge of ergonomic posture (those that had such knowledge gained it mainly from seminars or workshops, and health personnel). The most commonly reported health or treatment seeking behavior or choice was treatment chemist/over the counter drug, and this was closely followed by resorting to self-management.

3.3 Association between personal and job characteristics and prevalence of back pain

The association between personal and job characteristics, and prevalence of back pain is shown in Table 3. Prevalence was high (over 67%), even among those with only 1–5 years experience, and there was no significant association between years of experience working in automotive maintenance and prevalence.

The prevalence of back pain was highest in the 50–59 age group and lowest in the <20 age group. Older age was significantly associated with higher prevalence (p = 0.014). Differing weight status was also significantly associated with a prevalence of back pain (p < 0.001), and prevalence was highest in those of normal weight and lowest in the underweight. Similarly, increasing level of education was significantly associated with decreased prevalence, with prevalence highest among those with no formal education and lowest among those with tertiary education (p < 0.001). The association between job tasks and back pain was significant, with prevalence being highest among the welders and lowest among servicing men. Similarly, knowledge of ergonomics was significantly associated with decreased prevalence of back pain, with prevalence lowest among those who reported knowledge of ergonomic posture.

3.4 Post hoc analysis of association between personal characteristics and back pain

Table 4 shows the post hoc analysis of the significant association observed between age, daily working hours, and levels of education, weight status, job status, and most commonly adopted posture and prevalence of back pain. For the post hoc of age, the only significant results were those increase prevalence seen in those 50–59 years when compared to 20–29 years (p = 0.017), and 30–39 years (p = 0.019). There was a significant decrease in prevalence of back pain for those who worked 5–7 hours compared to those who worked at least 8 hours (p < 0.001). For post hoc analysis of educational status and back pain, higher education attainment was consistently associated with lower prevalence of back pain, except that those with no formal education and those with primary education had similar prevalence (p = 0.42). Similar significant associations were seen in all comparisons of weight status, except that between those of normal weight and the overweight or obese (p = 0.098).

Post hoc comparison of association between job tasks and prevalence of back pain were significant between panel beaters and electricians (p < 0.001), panel beaters and servicing men (p < 0.001), panel beaters and vulcanizers (p = 0.001), panel beaters and painters (p < 0.004), panel beaters and welders (p = 0.014), welders and service men (p = 0.015), repair and service men (p = 0.003), and cleaners and service men (p = 0.005). All other job task group comparisons were not significant. For post hoc analysis of the association between self-reported most adopted posture and prevalence of back pain, prevalence was significantly different for those who adopted mostly standing posture compared with those with sitting (p = 0.006), kneeling, bending, sustained posture (p = < 0.001s), squatting (p = 0.014), and repetitive movement (p = 0.001). Those who adopted mostly sitting posture differed in prevalence compared with those who adopted mostly squatting (p = 0.001), or lying (p < 0.001). Similarly, workers adopting mostly squatting showed a significant difference from those who adopted a lying (p < 0.001) or sustained posture (p < 0.001) as did those who adopted lying posture compared to those who adopted a sustained posture, repetitive movement or overhead reaching (p < 0.001s).

3.5 Factors predicting back pain among the participants

Multivariate analysis was done using a binary logistic regression model with a backward elimination method, to understand the effect of different job characteristics on the prevalence of back pain as dependent variable, among the automotive maintenance workers, as shown in Table 5. The multivariate analysis showed that the factors associated with back pain among the automotive maintenance mechanics were lack of job autonomy, inadequate task clarity, noise in the environment, manual handling, strenuous posture, heavy physical work load, vibration, work schedule, and inadequate auxiliary support.

4 Discussion

4.1 Prevalence reports

To our knowledge, this is the first study in Nigeria investigating back pain in the automotive sector. Our findings revealed that 12-month prevalence of backpain among the automotive maintenance workers was high, the low back being the most affected. This prevalence is higher than the 64.5% or 64.8% reported among professional drivers [16, 24], and the 65.6% among timber workers [14] in Nigeria. It is also higher than the prevalence reported among some automobile worker [25], including among Chinese [26, 27], Iranian [28], automobile workers. Low back was reported as the most affected body region with pain in a Chinesestudy [26].

The high prevalence of back pain seen in this group compared to other job settings in Nigeria, and to similar job settings in other countries, raises a public health issue. Certainly, the fact that about half the participants have been prevented from activity in the past 12 months by cases of back pain is cause for concern, and may indicate relatively high exposure to risk factors in these workers. Few of the workers had knowledge of ergonomic posture, demonstrating a need for awareness creation of work ergonomics among this group. Particularly, seminars and workshops should be aggressively pursued; and clinicians should include ergonomic education as a core component of interventions during back pain management. Back school is a particular area that may benefit these workers.

Among the different specialties of automotive work, welders had the highest prevalence. This can be attributed to the fact that welding entails bending, sustained static posture or a combination of several unsound postures. This is further corroborated by the fact that kneeling and sustained posture were the most adopted posture among the workers. This finding is in line with NIOSH [29], in which a relationship between these postural factors and back pain has been established. About three quarters of the respondents tried to mitigate their pain with over-the-counter drugs, self-medication or herbal treatment, and only about one quarter sought treatment from either a medical doctor or physiotherapist. Similar observations were reported by Burton et al. [30], among children and youths aged 10–19 years. What could explain this care seeking behavior among these workers even when majority (63%) reported that their back pain were severe? We did not investigate health believes in terms of seeking remedy among these group, neither did we asked question regarding accessibility to health services; or the level of satisfaction with their treatment choices. The question to also ponder is do these workers have enough health literacy to navigate the health system so as to access optimum care? These need to be answered by future research in this group.

4.2 Association with age

In this study, reported experience of back pain among the participants increased significantly with advancing age up to the 50–59 years old. This may suggest that these age groups are critical to back pain incidence among automotive mechanics workers; prospective research is needed to determine whether this is the case or are these time periods related to aging generally. In terms of the relationship between increasing age and prevalence of back pain, several authors [11 , 31] have shown evidence of this occurring in the general population.

4.3 Association with daily working hours

Our findings demonstrated that longer daily working hours (≥5hours) in automotive mechanic maintenance tend to lead to a rise in the prevalence of back pain. In a related job setting, Vyas et al. [20] found that workers who had worked for lengthy periods were at a higher risk than those who worked for shorter durations. This may be associated with fatigue related to long working hours, which may increase the risk of injury [31].

4.4 Association with weight status

Our study showed that weight status was not significantly associated with back pain. However, normal weight individuals had the highest prevalence while the underweight had the lowest prevalence. The lack of association between overweight and back pain was surprising, given the overwhelming evidence of the effect of increasing weight on the mechanical loading of the spine. The effects of decreasing loading intensity on back biomechanics have been examined, but whether being underweight confers an advantage in terms of predisposition to back pain is not known. Nevertheless, the high prevalence of back pain in the normal weight or low prevalence in the underweight may be connected to some other intervening variables outside weight status. Particularly, the weight back pain interactions reported were not gender and age specific as this objective is outside the scope of the present research.

4.5 Association with level of formal education

This study found an association between level of education and prevalence of back pain among the automotive maintenance workers. The highest prevalence of 12-month back pain was found among those with no formal education, and the lowest among those with tertiary education. Level of education has been shown to be inversely associated with work-related musculoskeletal discomforts [32], and use of traditional folk remedies of complementary and alternative medicine [33]. We did not study the relationship between level of education and remedy-seeking trends, but in a previous study it was found that increased level of education has a direct effect in health literacy, which in turn influences exposure to disease risks and health-seeking behaviours [34]. It could be suggested, therefore that people in this sector, comprising mainly individuals with primary education or less and with little knowledge of health issues, are at increased risk of exposure to work-related musculoskeletal disorders, particularly back pain, and are thus more likely to resort to unconventional remedies to treat back pain, as seen in our findings. Certainly, this triad is another public health issues in terms of wider determinants of industrial health.

4.6 Perceived work place stressors responsible for back pain

The study found that workers who lacked job autonomy, received inadequate task clarity or auxiliary support reported higher prevalence of back pain.Evidence of work psychosocial stressors and relationship with psychosocial stress symptoms including work-related musculoskeletal disorders are well documented in literature [35 –38]. One possible link between lack of job autonomy and back pain could be through a complex interaction with physical factors. Davis and Marras [39] suggest that physical fatigue is significantly increased during manual work under suboptimal conditions and the degree of interaction with psychosocial stressors including suboptimal job autonomy is highly predictive of pain. Supporting this theory, Clays et al. [40] stated that baseline low decision latitude (low control) correlated with the incidence of low back pain. Similarly, inadequate task clarity could put the worker at higher mental and psychological stress invariably eliciting the same cascade as would do inadequate auxiliary support. These were corroborated by Golabadi and colleagues in their findings [41].

And talking about physical stressors, in this study workers who had noise in the environment were at increased risk of back pain as do those with heavy physical work load, involved in manual handling or strenuous posture. Exposure to vibration and tighter work schedule were also found to be responsible for the reported back pain. How could be the possible links between these physical stressors and back pain in this occupational group? Individuals with high exposure to awkward trunk postures or an overall physically demanding job had a higher likelihood of incident LBP [42]. Also tighter work schedule among these worker mean higher tendency for fatigue related symptoms [41] thereby could prepare a pathway for back painvulnerability. This assertion is valid considering emerging biological link between fatigue and MSDs [39, 40]

These findings have wide implications, in that automotive maintenance industries in Nigeria are largely non-formal and poorly organized, and lack injury-prevention policies. Workers predominantly carry out maintenance tasks in the highly unsound conditions as seen during visits to this sites. Many who are undergoing apprenticeships are subjected to a heavy work load with rigid deadlines and inadequate job clarity. Additionally, the use of noise protective devices is lacking among Nigerian automotive maintenance workers, who are often exposed to noise in the workstations.

Much remains to be done. Legislation on minimum workstation safety standards, including wearing of appropriate industrial protective aids, is among the priority areas in this group. Also, occupational safety seminars and work shops for all those working in the automotive maintenance industry should be compulsory, while continuing education on safety precautions at work places should be an ongoing exercise for this group of workers.

5 Conclusion

The prevalence of back pain among automobile mechanics is higher compared to that of many countries. Majority of these workers do not seek consultation with a Doctor or a Physiotherapist even when majority of pain is severe and limit activity. Also knowledge of ergonomics is low in these workers. Factors associated with the back pain include strenuous work postures, lack of job autonomy, inadequate task clarity, heavy physical work load, noise in the environment among others. We suggest that health education programmes and measures directed towards prevention of occupational diseases would help to improve the health of automotive maintenance mechanics, particularly in decreasing the prevalence of back pain. Specifically, seminars and workshops should be aggressively pursued; and clinicians should include ergonomic education as a core component of interventions during back pain management. Back school is a particular area that may benefit these workers.

5.1 Limitations

First, the 12 months prevalence as well as the self-report prevalence of back pain implored in our study may be prone to recall bias. Also, social desirability bias may be a problem affecting the accuracy of the data due to the utilization of self-reported questionnaires as a major method of data collection. Again, the cross sectional design of our research at best explained associations; and a cause and effect relation betweenthe factors and back pain cannot be inferred. Interpretation should be done in light of these limitations.

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