Determinants of self-reported musculoskeletal

Determinants of self-reported musculoskeletal discomfort and disability
among commercial minibus (trotro) drivers in Accra Metropolis, Ghana: a
logistic regression analysis.
J.K Abledu1, E.B Offei1, G.K Abledu2, E Essuman3, B.O Essah2
1
School of Veterinary Medicine, University of Ghana.
2
School of Applied Science and Technology, Koforidua Polytechnic, Koforidua,
Ghana.
3
School of Public Health, University of Ghana.
Abstract
Background: Work-related musculoskeletal disorders (MSDs) cause substantial
morbidity and disability in the workplace, affect the quality of life and are inevitably
prevalent across a wide range of occupations. There are ample epidemiological
evidences, mostly in developed countries, less so in developing countries and almost
none in Ghana, to suggest that occupational driving is associated with increased risk
of (MSDs). This study, therefore, seeks to estimate the prevalence and determinants
of musculoskeletal discomfort and disability among a cohort of commercial minibus
(trotro) drivers in the Accra Metropolis of Ghana. Methods: This descriptive crosssectional study was conducted among drivers at four lorry terminals in the Accra
Metropolis of Ghana. All the eligible participants (n= 148) were assessed by using a
semistructured
questionnaire
that
included
the
standardized
Nordic
Musculoskeletal Disorder Questionnaire (NMQ). Results: The estimated prevalence
of musculoskeletal discomfort and disability among the population was 78.4% and
6.1% respectively.
After adjusting for possible confounders in multiple logistic
regression analysis, less physical activity (OR=4.9; 95%CI=1.5-16.5;p=0.010) , driving
>12 hours/day (OR=2.9; 95%CI=1.1-7.8; p=0.037) and driving >5 days/week (OR=3.7;
95%CI=1.4-9.4;p=0.007) emerged as significant risk factors of MSDs while marital
status and satisfaction of job were the main determinants of disability. Conclusion:
There is a need to educate drivers on safety and preventive strategies to reduce the
incidence of MSDs.
Key words:
Musculoskeletal disorders, disability, Nordic Musculoskeletal
Questionnaire, trotro.
Introduction
Commercial minibuses, popularly called ‘trotro’, play a critical role in Ghana’s urban
transportation system because of their ubiquitousness, easy accessibility and low
transport tariffs. However, there are concerns about public safety because of low
standards and poor maintenance of vehicle and deviant driver activities. That said,
the urban transport system in Ghana is usually marked by congested central areas
of the cities, high exposure to road accidents and poor environmental standards [1],
all of which could predispose drivers to a number of health-related problems,
including musculoskeletal disorders.
Musculoskeletal disorders (MSDs) are extremely common, causing considerable pain
and discomfort predominantly at the neck, shoulder and lower and upper back
regions, and in some cases, the extremities. MSDs cause significant morbidity and
disability and are a major economic problem [2], impact negatively on the quality of
life [3] and are a primary cause of health-related absences in the workplace [2 4].
The aetiologic risk factors of MSDs are varied and include awkward posture,
manual handling, heavy lifting, strenuous task and repetitive actions while the
pathogenesis is influenced by demographics, workload and psychosocial factors
[4].
Driving as a task involves prolonged sitting, a static and constrained posture,
vibration and muscular effort, all of which could lead to musculoskeletal discomfort
[5]. There are ample epidemiological evidences [6-17] to suggest that occupational
driving is associated with increased risk of MSDs. The prevalence of MSDs among
drivers varies between 53% to 91% in different parts of the world depending on the
type of vehicle, and is largely influenced by individual, physical (ergonomic) and
psychosocial risk factors [6 15 17 18].
Although several studies (mostly in developed countries) have explored and
reported extensively on musculoskeletal disorders among occupational drivers, few
studies have been conducted in developing countries and almost none in Ghana.
Estimates based on data obtained from developed countries may not accurately
reflect the situation in developing countries; therefore, the present study seeks to
estimate the prevalence and determinants of musculoskeletal discomfort and
disability (sickness absence) among a cohort of commercial minibus (trotro) drivers
in the Accra Metropolis of Ghana.
Methods
Participants
This epidemiological cross sectional survey was conducted among trotro drivers at
four lorry terminals in the Accra Metropolis of Ghana between January 2014 to
February 2014. Eligibility for participants was as follows: ‘trotro’ driver, aged 18
years or older with at least one year experience at the current job and having no
history of a disorder of the musculoskeletal system.
Data collection
Semi-structured questionnaires were administered at interview to 200 participants
while waiting at the lorry terminals. Participation in the study was voluntary and
informed consent was obtained from each participant. The three-part questionnaire,
which included the standardized Nordic Musculoskeletal Disorder Questionnaire
(NMQ) was used to determine participants’ socio-demographic variables such as
age, marital status, religion, education, alcohol consumption, smoking status and
level of physical exercise. Alcohol consumption was defined as the intake of at least
one bottle of an alcoholic beverage per week.
An individual was classified as a
smoker when he smoked at least one cigarette a day.
In addition, the questionnaire assessed occupational factors such as car ownership
and driving time profile (years of driving, total driving hours per day and number of
days per week of driving) and psychological factors such as self-perceived job stress
and job satisfaction of the participants.
Nordic Musculoskeletal Disorder Questionnaire (NMQ)
Musculoskeletal discomfort was assessed by the NMQ [19], a useful tool for
collection data on self-reported musculoskeletal discomfort and sickness absence.
The NMQ is a validated [19-21] tool and consists of a general questionnaire for
analysis of the point prevalence (7days), period prevalence (12months) and severity
or disability (effect on normal activities over the last 12 months) of musculoskeletal
trouble in different body areas such as neck, shoulders, elbows, wrists/hands, upper
back, lower back, hips/thighs, knees, and ankles/feet. The present study however
assessed the period prevalence of MSDs.
The NMQ was chosen because it is
standardized, widely accepted, easy to administer, saves time and cost involved in
constructing and piloting a new questionnaire.
Statistical Analysis
Data were categorized and analyzed with Statistical Package for Social Sciences
(SPSS) for Windows, version 20. (IBM Corporation, USA). First, univariate logistic
regression was used to obtain estimates of the prevalence odds ratio (POR) of
independent factors associated with MSDs and the associated disability. Significant
variables were entered simultaneously into a multiple logistic regression model to
obtain estimates of the adjusted POR. The Hosmer–Lemeshow test was used to
assess the goodness of fit of the model. In all statistical analyses, a value of p<0.05
was considered significant.
The logistic regression model
The logistic regression for the odds of the MSDs/disability is given by;
Odds (MSD/disability) = eβ0 * eβ1χ1 * eβ2χ2 * eβ3χ3….eβnχn
where,
β0, β1, β2, ... βn are the regression coefficients
χ1, χ2, χ3 …χn are the independent factors (e.g age, sex, etc)
eβ is the odds ratio (OR) for the independent variable X and it gives the relative
amount by which the odds of the outcome increase (OR > 1) or decrease (OR< than
1).
Results
Response rate and socio-demographic characteristics of the respondents
Out of the total 200 drivers that were contacted, 36 declined participation while 16
terminated
participation
when
passengers
arrived,
leaving
148
complete
questionnaires for final analysis. Participants’ sociodemographic characteristics are
presented in Table 1. The mean age of the participants was 33.0±10.6 years (range:
20-54 years). A majority of the participants were married (75.6%), Christians (79.1%),
primary and junior high school leavers (54.7%) and employee-drivers (82.4%). The
mean number of years of driving was 5.0±3.2 years while the average durations of
driving per day and per week were 12.4±2.2 hours and 4.9±0.7 days respectively (not
shown in the table). Many (74.3%) of the participants perceived their job as stressful
while 61 (43.9%) of them were dissatisfied with their current job. More than half
(56.1%) of them took alcoholic beverages, 23% smoked cigarettes while 14.2%
engaged in some form of sports/physical activities.
Table 1 Sociodemographic characteristics of participants (n=148)
Characteristic
n
Age (years)
<40
79
40-50
42
>50
27
Marital status
Married
112
Single
36
Education
Primary/Junior high school
79
Senior high school and equivalent
69
Religion
Christian
117
Moslem
31
Others
3
Type of driver
Owner
26
Employee
122
Perceived job stress
None
38
Yes
110
Job satisfaction
Satisfied
83
Dissatisfied
65
Alcohol
Yes
83
No
65
Smoking
Yes
34
No
114
Regular sports activities
23
Yes
125
No
Data is presented as frequencies and percentages. Total percentages
exactly 100% due to approximations.
%
53.4
32.4
18.2
75.6
24.3
53.4
46.6
79.1
18.9
2.0
17.6
82.4
25.7
74.3
56.1
43.9
56.1
43.9
23.0
77.0
15.5
84.5
may not be
Prevalence and pattern of musculoskeletal disorders and sickness absence
The results indicate that a total of 116 (78.4%) drivers suffered musculoskeletal
discomfort in at least one body region during the previous 12 months, out of which 9
(6.1%) drivers reported sickness absence (disability). The prevalence of the various
MSD domains are: low back pain (58.8%), neck pain (25%), upper back pain (22.3%),
shoulder pain (18.2%), knee pain (14.9%), ankle pain (9.5%), wrist pain (7.4%), elbow
pain (4.7%) and hip/thigh pain (2.7%) pain (Figure 1). In terms of disability, the
main contributing musculoskeletal discomfort were in the lower back (8 out 148
subjects), upper back (2/148 subjects) and knee (1/148 subjects) regions (Figure 1).
Figure 1 Prevalence and pattern of MSDs (plane bars) and sickness (black shade
bars) absence among the participants
Prevalence odds ratios of factors associated with MSDs and disability
Factors associated with MSDs and disabilities are recorded in Tables 2. Less physical
activity (OR=3.6; 95%CI=1.4-9.3; p<0.008), religion (i.e other religion apart from
Christianity)-OR=2.5; 95%CI=1.0-6.0; p=0.039, driving time >12 hours/day (OR=2.9;
95%CI=1.2-6.8; p=0.016), driving >5 days per week (OR=3.7; 95%CI=1.7-8.5; p=0.002),
self-perceived job stress (OR=3.6; 95%CI=1.6-8.2; p=0.003) and dissatisfaction of job
(OR= 4.5; 95%CI=1.7-11.7; p=0.002) were the significant variables that increased the
risk of MSDs in the univariate analysis.
After adjusting for possible confounders in
the multivariate analysis, the significant risk factors of MSDs were: less physical
activity, driving >12 hours/day and driving >5 days per week (Table 2). The model
was a good fit to the data (Hosmer-Lemeshow test: p=0.726) and explains about
34.7% of the observed variance.
Again in Table 2, factors that increased significantly (both univariate and
multivariate analysis) the risk of disability within the population were: being
married (unasjusted OR=7.3; 95%CI=1.7-30.8; p<0.007)/ (adjusted OR=6.6; 95%CI=1.528.9; p<0.013) and job dissatisfaction (unadjusted OR=11.5; 95%CI=1.4-94.5;
p<0.023)/(adjusted OR=10.4; 95%CI=1.2-88.0; p<0.031). The large confident intervals
could, in part, be due to the small sample size (n=148) and the low frequency of
disability (n=9). However, the model was a good fit to the data (Hosmer-Lemeshow
test: p=0.383), explaining 26.4% of the observed variance).
Table 2. Occupational and personal factors associated with MSDs and sickness absence
Musculoskeletal disorders
Characteristic
Age (years)
<40
40-50
>50
Marital status
Married
Single
Education
Primary/ junior high school
Senior high school equivalent
Religion
Christian
Muslim*
Alcohol
No
Yes
Smoking
No
Yes
Physical activity
Yes
No
n/N≠
OR (95% CI)
67/79
30/42
19/27
1
0.5(0.2-1.2)
0.9(0.3-2.8)
92/112
24/36
1
0.4(0.2-1.0)
61/79
55/69
1
1.2(0.5-2.5)
96/117
21/31
1
2.5(1.0-6.0)
48/65
68/83
1
1.6(0.7-3.5)
27/34
89/114
1
0.9(0.4-2.4)
13/23
103/125
1
3.6(1.4-9.3)
P value
n/N≠
OR (95% CI)
P value
0.121
0.900
2/82
5/39
2/27
1
3.2(0.4-23.9)
1.5 (0.1-3.0)
0.257
0.488
0.053
5/112
4/36
1
7.3(1.7-30.8)
0.007
0.713
4/79
5/69
1
2.4(0.6-10.0)
0.226
5/117
4/28
1
1.1(0.2-5.5)
0.923
0.238
5/65
4/83
1
0.6(0.2-2.4)
1
0.472
0.868
1/34
8/114
1
2.5(0.3-20.7)
0.398
1/23
8/125
1
1.5(0.2-12.6)
0.707
0.039
0.008
aOR (95% CI)
Disability
1
2.2(0.7-6.3)
1
4.7(1.4-15.8)
P value
0.170
0.011
aOR (95% CI)
P value
1
6.5(1.5-28.9)
0.013
Type of driver
Owner
22/26
1
2/26
1
Employee
94/122 0.6(0.2-1.9)
0.398
7/122
0.7(0.1-3.7)
0.706
Driving duration (years)
<5
34/48
1
4/46
1
5-10
46/59
1.8(0.6-5.2)
0.263
2/59
0.4(0-2.2)
0.290
>10
36/43
1.5(0.5-4.0)
0.471
3/43
1.4(0.2-10.3) 0.747
Driving time per day (hours)
≤12
20/32
1
1
1/32
1
>12
96/116 2.9(1.2-6.8)
0.016
2.8(1.0-7.5)
0.046 8/116 2.3(0.3-19.1) 0.441
Driving time per week (days)
<5
22/44
1
1
1/44
1
5-7
89/104 3.7(1.7-8.5)
0.002
4.0(1.5-10.2) 0.004 8/104 3.6(0.4-29.5) 0.236
Perceived job stress
None
23/38
1
1
1
1/38
1
Yes
93/110 3.6(1.6-8.2)
0.003
2.8(0.98.2)
0.066 8/110 2.9(0.4-24.0) 0.323
Job satisfaction
Satisfied
55/83
1
1
2/87
1
1
0.002
3.0(1.0-9.5)
0.058
7/61 11.5(1.4-94.5) 0.023 10.4(1.2-88.0) 0.031
Dissatisfied
61/65 4.5(1.7-11.7)
≠n/N- Number of subjects with MSDs/number of subjects in each category. * Muslims and other religions combined due to very low
frequency of the latter. OR-odds ratio; aOR-adjusted odds ratio; CI confidence interval; Hosmer-Lemeshow Goodness-of-Fit test (MSDs:
p=0.726; disability: p=0.383). Nagelkerke R-square (MSDs = 0.347; disability = 0.264)
Discussion
The prevalence and risk factors of MSDs among professional drivers would vary in
different countries due to differences in race (ethnicity), geographical location and
sociodemographic; however, to date, there is a paucity of data on MSDs of drivers in
the Ghanaian population. An earlier report (in press) found a 70.5% prevalence rate
of MSDs among taxi drivers in the Accra Metropolis, hence the need to replicate this
study among trotro drivers.
In the present study, 78.4% of the subjects suffered MSDs. This prevalence rate is
consistent with 53%-91% prevalence rates quoted in the world’s database for
professional drivers [6 15 17 18], and supports the hypothesis that professional
drivers are at increased risk of developing musculoskeletal troubles. Again,
musculoskeletal discomforts of drivers in this study were most common at the lower
back, occurring in 58.8% of the population. This figure is comparable to 60% among
truck drivers [6] and 60.4% [16] among commercial vehicle drivers in Malaysia, but
lower than 64.8 % [18] and 73.5% [22] reported among occupational drivers in
Ibadan and Kano cities respectively in Nigeria. Prevalence rates varying between
45.8% and 59% have been reported among taxi drivers [10 11 13 23], 40%-82% among
bus drivers [24] and 26% among a population of car drivers [15]. The observed
variation could, in part, be due to differences in population (race and ethnicity),
sample size, co-morbidities and methodological differences.
From this study, less physical activity (OR=4.9; 95%CI=1.5-16.5; p=0.010), driving >12
hours/day (OR=2.9; 95%CI=1.1-7.8; p=0.037) and driving >5 days/week (OR=3.7;
95%CI=1.4-9.4; p=0.007) were significant factors that increased the risk of MSDs
among the population. Although sports activity is said to have direct effects on
physical fitness and by extension, musculoskeletal health [10]; evidence for this
observation has been inconclusive [14], thus may warrant further research for
clarification.
Prolonged sitting as part of driving could exert tension on the spine,
thus leading to musculoskeletal discomfort [5].
A relationship between
musculoskeletal discomfort and duration of driving is supported by several studies
[10-12].
Religion, self-perceived job stress and dissatisfaction of job, all of which were
significantly associated with MSDs of drivers in this study, emerged as confounders
after multiple logistic regression analysis. The observed association between religion
and MSDs in this study could not be explained. On the other hand, psychological
factors such as self perceived job stress, job satisfaction and mental health have been
linked to increased risk of MSDs among drivers [11 12].
It is postulated that
psychosocial stress causes muscle tension, spinal cord strain and fatigue, any of
which could lead to traumatic injury [14].
However, some authors [15] found no
significant association between psychological factors and MSDs of drivers. Contrary
to previous studies [10 11 14 18], the present study found no statistically significant
association between musculoskeletal discomfort and age, number of years of
driving, alcohol drinking, smoking or ownership of vehicle.
Despite elevated prevalence of MSDs among the population, the observed
prevalence of disability was low (6.1%), with lower back pain, upper back pain and
knee pain as the main contributing symptoms.
Being single (unmarried) and
dissatisfaction of job were the significant factors (both univariate and multivariate
analysis) that increased the risk of disability among the population. Dissatisfaction
of one’s job due to low wage and low job support or lack of it, could lead to apathy,
and psychological stress of drivers; thus increase the likelihood of unwarranted
absenteeism among drivers. Also, psychosocial stressors have been postulated to
contribute to chronicity and disability of MSDs [25].
The reason why marriage
emerged as a determinant of MSDs among this cohort of drivers could not be readily
deduced from this study, but could simply be attributed to behavioral adaptation;
where unmarried men (usually with no spouse and children, hence less dependent
relatives) are more likely to deselect themselves from work.
The results of the Hosmer-Lemeshow test (MSD: p=0.726; disability: p=0.383)
supported the goodness of fit of the multiple logistic regression models presented in
Table 1. The Nagelkerke R2 values (MSD=0.347; disability=0.2640) indicate the multifactoral aetiology of MSDs and the associated disability. This cross-sectional study
could not account for all the possible risk factors of MSDs among this cohort of
participants. Further research is required.
Conclusion
The prevalence of musculoskeletal discomfort among trotro drivers in Accra
Metropolis is high (78.4%) and the resultant disability rate is 6.1%. The determinants
of MSDs among this population include less physical activity, driving more than 12
hour/day and more than >5days/week whereas marital status and satisfaction of job
are the main determinants of disability. There is a need to educate drivers on safety
and preventive strategies to prevent or reduce the incidence of MSDs.
Acknowledgement
We gratefully thank all the participants and research assistants.
Conflict of interest
There is no conflict of interest regarding this research.
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