Musculoskeletal Disorders among Oil Field Workers: Influences of Health Beliefs, Mental Health and Somatisation Tendency
Studies in recent years have suggested that health beliefs, mental health and
somatising tendency can affect musculoskeletal disorders (MSDs).The present
survey was conducted to determine the prevalence of MSDs among Iranian oil field
workers and their association with these psychological and physical risk factors.
A cross-sectional survey was carried out among 60 workers in one of the southern
oil fields of Iran in 2008. Data were collected using the standardized CUPID
questionnaire, administered through interviewing by a physician. Chi-square
(χ2) and logistic regression were used to analyze the data through
SPSS. About 86.7% of workers reported at least one MSD in the previous 12 months.
The most prevalent MSDs were knee pain (71%), low back pain (62%) and shoulder
pain (52%). Low back pain was significantly associated with health beliefs that
physical activity adversely effects back disorders. Neck, shoulder, elbow and
wrist/hand pain were each associated with somatising tendency and knee pain
was associated with climbing stairs and poor mental health. The prevalence of
MSDs among oil field workers is high. Somatising tendency is importantly associated
Received: April 23, 2012;
Accepted: September 19, 2012;
Published: December 18, 2012
At present musculoskeletal disorders are one of the most common occupational
health problems among working populations (Parot-Schinkel
et al., 2012). Work-related MSDs can increase disability (Andersen
et al., 2012), impair quality of life and lead to loss of work time
with financial consequences for the individual, employers and society (Tinubu
et al., 2010). MSDs are more prevalent in some occupations than others.
In a study of workers in Norways offshore petroleum industry over 12 years
(1992-2003), work-related MSDs made up half of all occupational diseases (Morken
et al., 2007).
In a British study, MSDs were reported to be the most prevalent health problem
among oil field workers, accounting for 23% of all sick bay consultations (Parkes
and Swash, 2005). Epidemiological studies have shown associations of MSDs
with individual factors, work-related risk factors such as handling loads, heavy
physical work and repetitive movements and psychosocial factors (Da
Costa et al., 2010; Larsson et al., 2007;
Ijzelenberg et al., 2004). WHO has classed musculoskeletal
disorders as multi factorial physical, organisational, psychosocial and sociological
risk factors (Kulin and Reaston, 2011). Moreover, in recent
years research has revealed that health beliefs, mental health and somatising
tendency also affect the MSDs (Palmer et al., 2008;
Solidaki et al., 2012; Leaver
et al., 2011).
Occupations in the oil extraction industry involve exposure to many of these
recognised risk factors (Morken et al., 2007).
Nevertheless, few studies of MSDs among oil field workers have been published
and none from Iran. This survey has been carried out to assess common musculoskeletal
complaints (low back, neck, shoulder, elbow, wrist/hand and knee pain) and their
associations with health beliefs, mental health and somatising tendency and
other risk factors among oil field workers in Iran.
MATERIALS AND METHODS
Study design and questionnaire: The study sample comprised all 60 of
the workers who were employed in one of the southern oil fields of Iran in 2008.
Participants worked in drilling, maintenance and repair, service and engineering
occupations. Data were collected using the standardized CUPID questionnaire
(Coggon, 2005), administered at interview by a physician.
This questionnaire covers demographic and organisational characteristics; aspects
of lifestyle (age, level of education, age of finishing full time education,
smoking, main occupation, duration of employment, weekly work hours), physical
and psychosocial factors at work (use of a keyboard, repeated movements of the
wrist or fingers, repeated bending and straightening of elbow, working with
hands above shoulder height, lifting weights of 25 kg or more by hand, climbing
up or down more than 30 flights of stairs a day, working under pressure by a
fixed time, decision-making, bonus, support from colleagues or supervisor, job
security, second job
.), musculoskeletal symptoms at each of six anatomical
sites (questions adapted from the Nordic questionnaire; Kuorinka
et al., 1987); health beliefs about the impact of physical activity
and work on MSDs (based on the Fear Avoidance Beliefs questionnaire; Waddell
et al., 1993); somatising tendency (elements of the Brief Symptom
Inventory (BSI) questionnaire; Derogatis and Melisaratos,
1983); mental health (questions from Short Form-36 (SF-36) questionnaire;
(Ware and Sherbourne, 1992; Montazeri
et al., 2005) and awareness of other people with MSDs. Validity and
reliability of questionnaire had been approved in other studies (Kuorinka
et al., 1987; Waddell et al., 1993;
Derogatis and Melisaratos, 1983; Ware
and Sherboune, 1992; Montazeri et al., 2005).
The questionnaire was translated from English into Persian and then was independently
back-translated to English with amendment of the Persian version where problems
were identified. Somatising tendency was graded to two and mental health to
three levels, according to scores for relevant sections of the questionnaire.
Interviews were conducted to obtain these data.
Statistical analyses: Statistical analysis was carried out with SPSS 18 software. In the first stage of the analysis, associations between every risk factor with pain in each body site (low back, neck, shoulder, elbow, wrist/hand and knee) were tested by χ2 test (or Fishers exact test, as needed). Then, all independent variables that showed significant associations with a p-value <0.05, were included in a backward stepwise logistic regression in order to investigate associations of all risk factors simultaneously. And they were summarised as Odds Ratios (ORs) with associated 95% Confidence Intervals (CIs). Age was included in the model independently of its p-value. The level of significance was set up at p<0.05.
Study population: All of the 60 men were eligible and agreed to take
part in the survey. There were no female oil workers. The ages of participants
ranged from 24-60 years, with a mean of 35.5 years. The average hours worked
per week in the two week periods when they were at work was 72.5 (range 70-84
|| Characteristics of study group
|Somatic distress score, Low: 0-7, Medium: 8-14, High: 15-22,
Mental health score, Low: 0-250, Medium: 250-375, High: More than 375
||Prevalence of musculoskeletal disorders in the past 12 months
among study group
Among subjects 48.3% had worked in their job for longer than five years and
21.7% smoked cigarettes. There were 38.3% in drilling jobs, 31.7% in service
jobs, 16.7% in maintenance and repair jobs and 13.3% in engineering jobs. Also
93.3% reported working under pressure to complete tasks by a fixed time. Table
1 summarises the individual and psychosocial characteristics of the study
Prevalence: The analysis of data showed that in this survey 86.7% of participants reported at least one musculoskeletal complaint in the previous 12 months. The highest prevalence rates were found for knee pain (71.1%) followed by low back pain (61.7%) and shoulder pain (51/7%). Table 2 presents the 12 month prevalence of complaints of back, neck, shoulder, wrist/hand, elbow, knee and each MSDs.
Among the study group 15% reported pain only in one region of body, 58.4% in
2-5 regions and 15% in all six regions (low back, neck, shoulder, elbow, wrist/hand,
knee pain). The highest prevalence of MSDs was in drilling occupations.
Potential risk factors: All variables in the first stage of the study (using χ2 and fishers exact tests) showed significant associations with each MSDs, with a p-value <0.05. Subsequently, the variables along with the variable of age were included in a multivariate logistic regression model (Table 3). In the final model of stepwise logistic regression analyses, low back pain was significantly associated with a belief that physical activity should be avoided when the symptom occurs (OR = 4.6) (95% CI 1.2-17.3). This means people with this avoidance belief are exposed 4.6 times more to the risk of LBP.
The neck pain associated with knowing people at work who suffered from neck
pain in the past 12 months (OR = 11.9) (p-value = 0.030) and somatisation tendency,
the OR in the medium and high versus the low band of somatisation tendency was
4.5 (95% CI 1.2-17.8). The shoulder, elbow and wrist/hand pain also associated
with somatisation tendency. Risk of these pains tended to increase according
to the score of somatic symptoms. The ORs for shoulder pain, elbow pain and
wrist/hand pain were 6.9 (95% CI 1.8-26), 9 (95% CI 2.1-38.8) and 5.9 (95% CI
1.7-20.1), respectively. The results also showed knee pain associated with mental
health (OR = 8.8) and climbing up or down more than 30 flights of stairs a day
OR = 10.8) (p-value = 0.006).
|| Association with prevalent musculoskeletal disorders: results
from the multiple regression backward analysis
|Mental health score; Low: 0-250, Medium; 250-375, High: More
than 375, Variable(s) entered on step 1 regression model for; Low back pain:
Age, belief in avoiding physical activity in low back pain, lifting weights
of 25 kg or more by hands, knowing anyone at work who has had low back pain,
somatic distress, Neck pain: Age, deciding about work time table and breaks,
knowing anyone at work who has had neck pain, knowing anyone outside work
who has had neck pain, somatic distress, Shoulder pain: Age, somatic distress,
working for longer than one hour with your hands above shoulder height,
knowing anyone at work who has had arm, hand/shoulder pain, Elbow pain:
Age, main occupation, somatic distress, Wrist/hand pain: Age, knowing anyone
at work who has had arm, hand/shoulder pain, somatic distress, Knee pain:
Age, main occupation, climbing of stairs, somatic distress and mental health
Thus, the OR for knee pain increased 8.8 times more in workers in the highest
versus the lowest band for the SF-36 mental health score.
The present study showed that prevalence of musculoskeletal complaints among
Iranian oil field workers was high (86.7%) and higher than that in a similar
study in China (56%) (Chen et al., 2005). In
a study by Choobineh et al. (2009), among workers
of an Iranian sugar-producing factory 87.1% reported musculoskeletal disorders
in the past year while a study by Karimfar et al.
(2008) showed that 77.6% of workers in the Zinc Industry reported at least
one MSD in the previous 12 months. The highest prevalence was reported in the
lower back (47.9%).
In the present study the most prevalent MSD was knee pain (71.7% of all subjects
and 82.7% of those with musculoskeletal pain), whereas in most other studies
back pain has been more prevalent than other musculoskeletal disorders. For
example, in the offshore petroleum industry in Norway, back and knee problems
accounted for 20 and 12% of work-related musculoskeletal disorders over 12 years
(Morken et al., 2007).
Moreover, in China, the most prevalent MSD in the past year among oil field
workers was low back pain 32% (Chen et al., 2005).
In a similar longitudinal British survey conducted in 2000-2005, LBP was reported
34 and 46%, respectively (Parkes, 2008).
Fernandes and Carvalho (2000) surveying among 1,026
oil drilling workers in northeast Brazil indicated an overall prevalence rate
of 5% for intervertebral disc disease, with rates of 1.8% among people who did
not carry heavy loads, 4.5% among people who sometimes carried heavy loads and
7.2% among those who usually carried heavy loads. In a study of car manufacturing
workers in Iran, the reported prevalence of back pain in the past year was 51.1
and 81.8% among workers who had to lift heavy loads (Dehghan-Manshady
et al., 2003). The relationship between lifting heavy loads and low
back pain has been recognised for many years (Elders and
Burdorf, 2004; Andersen et al., 2007). In
the present study, almost all participants (88.3%) reported lifting heavy loads
and therefore it was not possible to draw meaningful conclusions about the association
of low back pain with lifting.
We did, however, find a significant association of back pain with health beliefs
about avoidance of physical activity when the symptom occurs, a finding that
has also been previously reported by Waddell et al.
(1993). Andersen et al. (2007) reported a
similar association for back and also other regional musculoskeletal pain. It
is probable that people who suffer from back pain are more aware that physical
activities exacerbate their symptoms and therefore think that they should be
avoided. However, it is also possible that beliefs about the influence of physical
activity on back pain predispose people to getting back problems. A longitudinal
study would be needed to test this.
Neck pain was associated with knowing other people at work with neck pain (OR = 11.9). It could be that greater awareness of MSDs predisposes people to be troubled by such symptoms. Alternatively, it might be that when people have pain, they talk about it to others and then find out about other people's pain as a consequence.
Neck, shoulder, elbow and wrist/hand pain all showed significant associations
with somatising tendency. Similar associations have been observed in other studies
(Warnakulasuriya et al., 2010). In Greece, Solidaki
et al. (2012) found that pains at two or more anatomical sites were
associated with somatisation tendency. A study in New Zealand by Harcombe
et al. (2010) indicated weak associations of somatisation with musculoskeletal
pain at most sites. In addition, Matsudaira et al.
(2011) in a study of four occupational groups in Japan found that somatising
tendency was the strongest risk factor for musculoskeletal disorders.
In the present study, shoulder pain with prevalence of 51.7% is in the third
position after other musculoskeletal disorders which is higher than that (22
and 29%) in a similar British longitudinal study (Parkes,
According to the results, the highest rates of all of MSDs were found in workers
of drilling group but in a study by Morken et al.
(2007) in oil field, workers of maintenance and repairing reported the highest
prevalence and also significant relationships were indicated between musculoskeletal
disorders of upper, lower extremities, low back and neck pain with four job
groups of oil fields.
In this study, knee pain was significantly associated with climbing up or down
of stairs. Baker et al. (2003) have previously
linked repetitive climbing of stairs with an increased risk of meniscal tear
in the knee and in another study in an oil field 10% of workers reported walking
on hard surfaces and climbing stairs and ladders as reasons of musculoskeletal
disorders (Morken et al., 2007).
We also found that knee pain was associated with poor mental health. People
who reported low mental health had knee pain 8.8 times more than those who reported
high mental health. In another study, poor mental health was associated with
increased risk of both knee pain and associated disability (OR = 2.1, OR = 4.7)
(OReilly et al., 1998).
Sagmanli et al. (2009) in Turkey showed significant
positive correlation between low back pain intensity and emotional status while
Parkes and Swash (2005) reported an association between
poorer mental health and greater number of MSDs consultations. In a study by
Antonopoulou in Greece, among all aspects of quality of life and all MSDs, the
mental health domain was influenced only by knee pain (Antonopoulou
et al., 2009). In a study in Japan among nurses, computer operators,
sales/marketing personnel and transportation operatives, people who reported
poor mental health had 1.4 fold higher risk of musculoskeletal pain at ≥3
body sites (Matsudaira et al., 2011). Also, in
a study using the Short Form 36 questionnaire, regional pain at four sites (elbow,
forearm and hand; low back; hip, knee, foot and neck/shoulder) was associated
with poor mental health and vitality (Andersen et al.,
2007). Warnakulasuriya et al. (2010) in a
study among 852 participants in four occupational populations in Sri Lanka found
MSDS pain was strongly associated with low mood. Part of this association may
occur because musculoskeletal pain causes mental distress but poor mental health
may also predispose people to the development of musculoskeletal symptoms.
This study found prevalence of musculoskeletal complaints and especially of knee pain, among oil field workers is high. The most consistent risk factor for symptoms was tendency to somatize, an association that has been observed in other countries and occupational groups. In addition, back pain was associated with beliefs about adverse effects of physical activity and knee pain with low mood and frequent climbing of ladders or stairs. A follow-up longitudinal study could help to establish the extent to which the associations with psychological variables are causal.
The authors would like to express their special thanks to Prof. David Coggon of the MRC Epidemiology Resource Centre, University of Southampton, UK, for his assistance in this research and his valuable comments in the preparation of this study. We are also thankful to research deputy of Shahroud University of Medical Sciences for financially supporting this study.
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