Physical and psychosocial risk factors for musculoskeletal disorders in New Zealand nurses, postal workers and office workers
Helen Harcombe1, David McBride1*, Sarah Derrett2 and Andrew Gray1 1
Department of Preventive and Social Medicine, University of Otago, Dunedin, New
Zealand 2
Injury Prevention Research Unit, Department of Preventive and Social Medicine,
University of Otago, Dunedin, New Zealand
* Corresponding Author: Dr David McBride, Department of Preventive and Social Medicine, University of Otago, PO Box 913, Dunedin 9054, telephone 03 479 7208, fax 03 479 7298, email
[email protected]
Word count Article: 2606 Abstract: 247
Number of tables: 4
Short running head: MSDs in New Zealand nurses, postal workers and office workers
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ABSTRACT Objective To investigate the association of physical and psychosocial risk factors with musculoskeletal disorders (MSDs) in New Zealand nurses, postal workers and office workers. Design A cross-sectional postal survey asking about demographic, physical and psychosocial factors and MSDs. Participants A total of 911 participants were randomly selected; nurses from the New Zealand Nursing Council database (n=280), postal workers from their employer’s database (n=280) and office workers from the 2005 electoral roll (n=351). Outcome measures Self-reported pain in the low back, neck, shoulder, elbow, wrist/hand or knee lasting more than one day in the month prior to the survey. Results The response rate was 58%, 443 from 770 potential participants. 70% (n=310) reported at least one MSD. Physical work tasks were associated with low back (OR 1.35, 95% CI 1.14-1.6), shoulder (OR 1.41, 95% CI 1.17-1.69), elbow (OR 1.14, 95% CI 1.13-1.83) and wrist/hand pain (OR 1.39, 95% CI 1.15-1.69). Job strain had the strongest associations with neck pain (OR 3.46, 95 CI 1.30-9.21) and wrist/hand pain. Somatisation was weakly associated with MSDs at most sites. Better general and mental health status were weakly associated with lower odds of MSDs.
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Conclusions In injury prevention and rehabilitation the physical nature of the work needs to be addressed for most MSDs, with modest decreases in risk seemingly possible. Addressing job strain could provide significant benefit for those with neck and wrist/hand pain, while the effects of somatisation and promotion of good mental health may provide smaller but global benefits. Key words Musculoskeletal diseases, occupational exposure, psychosocial factors. Key messages What is already known on this subject •
New Zealand nurses, postal workers and office workers have a high prevalence of MSDs
•
Personal, work organisation and work related psychosocial factors are all associated with MSDs
What this study adds •
Physical work tasks were associated with MSDs of the low back, shoulder, elbow and wrist/hand
•
The strongest associations were seen between job strain and neck and wrist/hand complaints
•
A greater number of non-physical factors were associated with neck pain
•
Somatisation had a small, but global, association; better mental health status was associated with a lower odds of neck and shoulder disorders
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INTRODUCTION Musculoskeletal disorders (MSDs) are a leading problem in nearly all industries, from those involving heavy manual work to those with more sedentary activities. In the general population these conditions are also common;[1] they “are the most frequent causes of physical disability, at least in developed countries.”(p.158)[2] Risk factors are multifactorial and include physical and socio-organisational factors at work, and also cultural and personal factors, and this complex model needs to be understood in order to modify the risks.[3] Physical factors are probably best understood.[4] Socioorganisational factors (job control, demand and support) and personal factors (general and mental health) have been studied but are less well understood. An emerging factor, a tendency to worry about disease (somatisation) is now under investigation in an international longitudinal study, Cultural and Psychosocial Influences on Disability (CUPID). The relative importance of these factors and how they differ in their effects across common occupations, and internationally, is not yet well understood.
A previous report showed a high prevalence of MSDs in nurses, postal workers and office workers at base-line in this New Zealand component of the CUPID study.[5] Few studies have investigated risk factors for MSDs in these New Zealand workers. A prospective study included nurses in an investigation of risk factors for acute low back pain becoming chronic[6] and a cross-sectional study has investigated risk factors for MSDs in clerical workers and cleaners.[7] Other studies report MSD prevalence differed among workers in the same occupational groups, for example low back pain was more common among nurses who worked on particular wards[8] and the prevalence of upper limb pain was higher among keyboard workers compared to nonkeyboard workers in a study of clerical workers.[9] To our knowledge no other
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studies have investigated risk factors for MSDs in these ‘at risk’ New Zealand workers. This paper describes the association between physical and psychosocial risk factors and MSDs in New Zealand nurses, postal workers and office workers. METHODS Design A cross-sectional postal survey of nurses, postal workers and office workers using computers. The study received ethical approval from the New Zealand Multi-Region Ethics Committee. Study participants The CUPID study required participants to be aged between 20 and 59 years, working in one of the three target occupations and in their current job for at least a year. They also had to be resident in New Zealand at the time of the survey in 2007. Power calculations were conservatively based on the lowest one-month prevalence estimate (40%) of MSDs lasting for at least seven days in the general population of New Zealand reported by Taylor.[10] A minimum of 350 completed responses allowed us to investigate up to 14 predictors simultaneously (as this would give 140 cases) using the recommendations of Peduzzi.[11] Taking factors such as an anticipated response rate of 50%, stability of employment and accuracy of self-reported occupation on the electoral roll into account, a total of 911 workers were randomly selected and invited to participate in the study. Nurses were selected from the New Zealand Nursing Council database (n=280), postal workers from an employer’s database (n=280) and office workers from the New Zealand 2005 electoral roll (n=351). Definition of injury MSDs were defined as self-reported pain at the low back, neck, shoulder, elbow, wrist/hand or knee lasting for more than a day in the month prior to the survey.
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Questions were similar to the Standardised Nordic Questionnaires for MSDs and were accompanied by a diagram showing the area of the body in question.[12] Survey The UK CUPID team designed a core questionnaire developed from previous research (for example Palmer 2001[13] and Smedley 2003[14]) including demographic, physical and psychosocial factors. Additional items, specific to the New Zealand survey were also included such as a measure of general health status. Eight physical work tasks (Table 1) were aggregated to give a ‘total task score.’ Psychosocial work factors were assessed by the Whitehall II psychosocial work questionnaire.[15] This consists of 25 questions in three principal domains, recoded so that high scores equal high job control, high job demands and high support. Scores were added for each subscale and divided into high medium and low tertiles. High job strain was defined as low control-high demands, low job strain was high control-low demands and medium job strain was the remainder (low-low, high-high or medium in either subscale.) Seven questions from the Brief Symptom Inventory (BSI)[16] were used to investigate somatisation. Each item was scored on a five point scale (0-4) with total possible scores of 0-28. Because two BSI questions could relate directly to MSDs (numbness or tingling, and feeling weak) somatisation scores were also calculated omitting these items. Mental health status was assessed by the Mental Health Inventory-5,[17] five items each with a six point scale; self-efficacy using the General Self-Efficacy Scale,[18] ten items scored from one to four (possible scores 10 to 40), and general health status using the EQ-5D.[19] The length of time participants had been in their current job was classified as one to five years or greater than five years. Participants were asked how secure they felt their job would be if they had a significant illness that kept them off work for three months
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(job security) with four possible response options which were dichotomised for analysis (ie low/high job security). Job satisfaction was assessed by asking how satisfied participants had been with their job as a whole, taking everything into consideration. The four possible responses were once again dichotomised for analysis (ie low / high job satisfaction.)
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Table 1:
Physical work tasks on an average working day
Work characteristic Keyboard or typewriter use for more than 4 hours in total Repeated wrist or finger movements for more than 4 hours in total Repeated bending and straightening of the elbow for longer than 1 hour in total Reaching, pushing or pulling Hands above shoulder height for more than 1 hour in total Lifting weights 25kg or more by hand Climbing up or down more than 30 flights of stairs Kneeling or squatting for longer than 1 hour in total
Statistics MSDs were investigated by anatomical site considering all occupational groups together. The association between risk factors and each site of MSD was analysed by multiple logistic regression adjusting for occupation, age, sex and body mass index (BMI). Fewer participants reported elbow pain so, for this type of MSD, only occupation and age were entered into the model. Physical work tasks were also adjusted for when analysing psychosocial factors. Data were analysed using Stata 9 statistical software.[20] RESULTS Of the 911 people invited, there were 770 eligible participants; of these 443 (58%) agreed to participate. Of the 443 participants, low back pain was reported by 31% (n=136), neck pain by 29% (n=128), shoulder pain by 27% (n=120), elbow pain by 12% (n=52) , wrist/hand pain by 23% (n=104) and knee pain by 22% (n=98).
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Table 2 shows the work organisational factors investigated. Physical work tasks showed weak but significant associations with MSDs of the low back, shoulder, elbow and wrist. The remaining factors showed no significant effects.
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Table 2:
Work organisational factors
Sample size (n=443)
LBP (n=136)
Neck (n=128)
Shoulder (n=120)
Elbow (n=52)
Wr/hand (n=104)
Knee (n=98)
p-value
p-value
p-value
p-value
p-value
p-value
Variable (reference)
OR (95% CI)
OR (95% CI)
OR (95% CI)
OR (95% CI)
OR (95% CI)
OR (95% CI)
Time in job (1-5 years)
0.301
0.308
0.554
0.983
0.093
0.515
1.32 (0.78, 2.23)
0.77 (0.46, 1.28)
1.18 (0.68, 2.04)
1.01 (0.50, 2.02)
0.61 (0.34, 1.09)
1.22 (0.69, 2.24)
0.403
0.319
0.840
0.652
0.675
0.983
0.77 (0.41, 1.43)
1.36 (0.74, 2.49)
1.07 (0.56, 2.04)
0.80 (0.65, 2.07)
0.85 (0.41, 1.78)
1.01 (050, 2.04)
0.598
0.721
0.615
0.168
0.965
0.584
1.15 (0.68, 1.97)
0.91 (0.52, 1.56)
1.16 (0.65, 2.07)
1.73 (0.79, 3.79)
0.99 (0.53, 1.82)
0.85 (0.47, 1.52)
0.768
0.092
0.525
0.876
0.202
0.622
Regular night shift
0.71 (0.28, 1.79)
2.81 (1.05, 7.48)
0.66 (0.26, 1.66)
0.94 (0.28, 3.22)
1.89 (0.64, 5.55)
1.56 (0.52, 4.62)
Other
0.87 (0.38, 1.97)
1.15 (0.45, 2.96)
0.63 (0.26, 1.55)
1.33 (0.37, 4.75)
2.69 (0.88, 8.23)
1.55 (0.57, 4.23)
0.723
0.230
0.973
0.421
0.681
0.264
1.00 (0.98, 1.03)
1.01 (0.99, 1.04)
1.00 (0.98, 1.02)
1.01 (0.98, 1.05)
1.01 (0.98, 1.03)
1.01 (0.99, 1.04)
0.402
0.110
0.335
0.547
0.734
0.227
1.01 (0.99, 1.03)
1.02 (1.00, 1.04)
1.01 (0.99, 1.03)
1.01 (0.98, 1.04)
1.00 (0.98, 1.03)
1.01 (0.99, 1.04)
0.001
0.294
5 years Contract type (permanent) Other Work schedule (regular day) Other Type of shift (regular day)
Hours/week main job
Hours/week total jobs
Physical work tasks
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Table 3 presents psychosocial work factors. Job strain showed the strongest association with MSDs, with statistically significant associations for neck and wrist/hand pain and an increased OR for low back pain.
Job dissatisfaction was significantly associated with shoulder MSDs, with a non-significantly elevated risk for low back pain.
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Table 3:
Psychosocial work factor associations with MSD reported at specific anatomical site
Sample size (n=443)
LBP (n=136)
Neck (n=128)
Shoulder (n=120)
Elbow (n=52)
Wr/hand (n=104)
Knee (n=98)
p-value
p-value
p-value
p-value
p-value
p-value
Variable (reference)
OR (95% CI)
OR (95% CI)
OR (95% CI)
OR (95% CI)
OR (95% CI)
OR (95% CI)
Job satisfaction (satisfied)
0.064
0.418
0.022
0.938
0.469
0.747
1.86 (0.96, 3.60)
0.73 (0.34, 1.56)
2.23 (1.12, 4.43)
1.04 (0.38, 2.89)
0.73 (0.31, 1.71)
0.88 (0.39, 1.96)
0.546
0.808
0.208
0.271
0.664
0.520
0.84 (0.48, 1.48)
1.07 (0.61, 1.87)
1.43 (0.82, 2.51)
0.62 (0.26, 1.46)
1.15 (.62, 2.12)
0.81 (0.42, 1.54)
0.068
0.029
0.342
0.169
0.023
0.288
Medium
2.45 (1.12, 5.37)
1.43 (0.69, 2.98)
1.58 (0.72, 3.49)
1.95 (0.65, 5.92)
4.13 (1.40, 12.22)
2.01 (0.84, 4.86)
High
2.85 (1.01, 8.03)
3.46 (1.30, 9.21)
2.18 (0.76, 6.24)
0.61 (0.10, 3.73)
2.33 (0.57, 9.51)
2.07 (0.64, 6.71)
0.056
0.890
0.290
0.694
0.449
0.360
Medium
0.59 (0.34, 1.01)
1.06 (0.62, 1.81)
0.75 (0.43, 1.32)
0.98 (0.48, 2.00)
0.90 (0.50, 1.63)
0.64 (0.34, 1.18)
High
0.56 (0.32, 0.96)
0.92 (0.53, 1.59)
0.64 ( 0.36, 1.14)
0.72 (0.33, 1.59)
0.67 (0.36, 1.26)
0.80 (0.44, 1.46)
Dissatisfied Job security (safe) Unsafe Job strain (low)
Social support (low)
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Somatisation showed consistent and significant but weak associations with MSDs. After excluding the variables potentially associated with MSDs, (numbness or tingling, and feeling weak), somatisation was no longer associated with shoulder pain (p=0.061) but remained associated with low back, neck and knee pain. Better general and mental health was associated with lower odds of shoulder pain and mental health with neck pain.
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Table 4:
The association between personal factors and risk of MSDs
Sample size (n=443)
LBP (n=136)
Neck (n=128)
Shoulder (n=120)
Elbow (n=52)
Wr/hand (n=104)
Knee (n=98)
p-value
p-value
p-value
p-value
p-value
p-value
Variable
OR 95% CI1
OR 95% CI
OR 95% CI
OR 95% CI
OR 95% CI
OR 95% CI
Somatisation2
0.001
0.001
0.015
0.359
0.062
0.001
1.10 (1.04, 1.16)
1.10 (1.04, 1.16)
1.07 (1.01, 1.13)
1.03 (0.97, 1.10)
1.06 (1.00, 1.12)
1.11 (1.04, 1.18)
0.991
0.167
0.655
0.410
0.638
0.648
1.00 (0.95, 1.05)
0.96 (0.91, 1.02)
1.01 (0.96, 1.07)
1.03 (0.96, 1.11)
0.99 (0.93, 1.05)
1.01 (0.95, 1.08)
0.277
