The link between workplace stressors and physical injury: A cross-sectional study

Given the human, industrial and societal costs of Musculoskeletal Disorders (MSDs), the aim of this project was to (i) provide up to date prevalence estimates of MSDs among NSW employees in 2020-2021, (ii) estimate the associations of physical, psychosocial, and demographic factors with MSDs among NSW employees, specifically evaluating the Psychosocial Safety Climate (PSC) as a distal cause of MSD outcomes, and (iii) utilise the longitudinal strengths of the Australian Workplace Barometer survey to evaluate prospective physical and psychosocial process paths to MSDs in a wider population of employed Australians based on matched data from NSW, WA and Victoria with a lag of 6 years.

Data on MSDs and associated treatment, together with potential demographic and workplace risk factors were collected via telephone interview data from 628 NSW employees. Workplace risk factors included psychosocial risks (e.g., job demands, job control, social support, harassment, bullying), PSC, and physical risks (e.g., moving/lifting heavy loads, repetitive actions, rapid and continuous physical activity, working for long periods with head/ body or arms in physically awkward positions). Psychological distress was assessed in terms of burnout and depressive symptoms.

We focused on three main MSD specific outcomes; (i) pain, (ii) doctor diagnosed MSDs (e.g., carpal tunnel syndrome, chronic back pain, rotator cuff problem), and (iii) workplace injury.

Statewide and industry-specific prevalence estimates of MSDs and associated outcomes were weighted for age and sex, using weights and estimates generated from the NSW sample in the 2016 ABS census and the Household, Income and Labour Dynamics in Australia (HILDA) panel survey.

In a cross-sectional analysis, we estimated associations of a broad range of risk factors with MSDs. We then investigated poor PSC as a distal cause of MSDs via three paths using regression models:

• Path 1: PSC is negatively related to physical demands that in turn positively relate to MSDs (a physical mechanism);
• Path 2: PSC is negatively related to psychosocial risk factors that in turn positively relate to MSDs (a psychosocial mechanism); and,
• Path 3: PSC is negatively related to psychosocial risk factors that in turn positively related to psychological distress and in turn MSDs (psychosocial extended).

We then repeated this investigation in a longitudinal path analysis again testing the hypothesis of poor PSC as a distal cause of MSDs in 432 Australians employed over 6 years.

Across the sample of 628 NSW employees, one quarter (26%) of respondents reported being in a lot of pain in at least one body area, and only 21% reported no pain in any area. Around 20% of women and 22% of men indicated they had received a lifetime doctor diagnosis of any of the common chronic MSDs, and a half (49%) of those reported being in a lot of pain. The most common doctor diagnosed MSD for both men and women was chronic back pain or sciatica (6%) and osteoarthritis in women (6%). Injuries in the past year were reported by 11% (70/628), and of these 31% (22/70) were work-related. Around 2.5% of employees had made a worker’s compensation claim in the past year.

The different methods of assessing MSDs and related symptoms produce different results for both prevalence and risk analysis.

For MSD related pain, NSW industries with the highest estimated prevalence of employees reporting a lot of pain from MSDs were Retail Trade, Electricity Gas and Waste Services (both around 35%), and Financial/Insurance, and Professional Scientific/Technical Services (both > 25%). Fewer than 15% of employees in Mining, Construction, Education, Public Administration, and IT reported high pain levels.

For doctor diagnosed MSDs, the industry variability in prevalence was lower, with no statistically significant differences between them and a range of 10-23%.

For a 12 month work-related injury, there was a low prevalence of 4% (22/628) and not surprisingly there were no significant differences between industries, although the prevalence was 10% or higher in Electricity Gas Water and Waste Services, Transport, Postal and Warehousing, and Wholesale Trades industries and less than 1% in Finance.

Taking into consideration the results from both cross-sectional and longitudinal analysis (considering the effects of risks over 6 years) it is clear that workplace physical risk factors are negatively associated with MSDs. Over and above these effects, there was some support for a psychosocial mechanism. Cross-sectionally psychosocial factors such as psychological demands (work pressure) and workplace harassment were positively related to psychological distress (depression) that in turn related positively to MSD pain. Burnout was directly related to the work injury. Longitudinally workplace autonomy (skill discretion and decision latitude) emerge as a more important factor for predicting future pain and workplace injury. A novel finding was that skill discretion appeared linked to MSD pain via physical demands, highlighting a new mechanism – how psychosocial mechanisms relate to physical mechanisms. Since PSC was related to psychosocial factors and distress, and sometimes directly related to MSDs there is some support for the proposition that PSC is an indicator of MSDs. The plausible risk factors for MSD pain (as an exemplar) are summarised in the figure below.

Some demographic factors were also significant risks: MSD diagnosis was more common among older workers, MSD pain more common among women workers.

Given the important role of physical demands, we tested longitudinal models predicting future physical workplace risks. In this analysis since we were predicting future work conditions, we included only workers (n = 269) who were in the same organization at both T1 and T2. As expected, physical demands predicted future physical demands. Autonomy in the form of skill discretion was negatively related to future physical demands work, after controlling for baseline physical demands. Psychological distress (burnout, depressive symptoms) was not related to future exposure to physical demands. This is an important point since it gives more weight to these working conditions, rather than an overall negative view of the individual workers, as an explanation for future exposures.

Figure 1. Plausible pathways to workplace MSDs

In sum, the emergence of MSDs in the workplace is difficult to predict. The impact of high workplace physical demands, low PSC, skill discretion, decision authority and psychological health status many years earlier are variable depending on MSD outcomes. High levels of workplace physical risks are easier to predict and the most consistent risk factor for these is psychosocial - lower levels of autonomy at work. In occupations where workers are exposed to low skill discretion and decision authority, this may imply that local actions cannot be taken by employees to reduce or manage physical demands (less agency), resulting in increased risk for MSDs.

Given the impact of workplace factors on MSDs and that some risks identified are preventable or modifiable, action should be taken to target these. Physical demands should be reduced or controlled. Action should be taken to improve PSC, improve skill discretion, reduce harassment, and reduce work pressure. Although we have identified some factors that are associated with MSDs and psychological health the predictive effects are small and targeting each will have only a small effect. However, across employees over a whole NSW state, this could have some reasonable population effects.

Duty holders under WHS laws should consider plans to implement control strategies for the physical and psychosocial risks identified. The finding that psychosocial factors play a substantive role in MSDs supports emerging research and requires a fresh preventive approach. A novel intervention not yet tried to improve MSD status among employees would be to focus on improving PSC. Since PSC is antecedent to many risk factors, focusing on improving PSC would be an efficient focus, and is achievable in a short period (Dollard & Bailey, 2021), and would have the added benefit of increasing workplace mental health.

Our research suggests that interventions focused on the following industry sectors reporting the most MSD pain in this study might be beneficial: Retail Trade, Electricity Gas and Waste Services, Financial/Insurance, Professional Scientific/Technical Services, Rental Hiring and Real Estate Services, Agriculture and Fishing, and Administrative and Support Services.

In conclusion, MSDs represent a complex issue for workplaces and workplace research. When assessing MSDs in an organisational context our multidimensional approach highlights huge variability in prevalence and risks depending upon how MSDs are conceptualised and measured. The low prevalence of MSDs in some physically demanding industries such as mining may reflect good work health and safety practices, or alternatively may not be indicative of incidence but rather represents people with MSDs leaving these industries (healthy worker effect).

This study shows that pain linked to MSDs is a very common symptom in NSW employees, regardless of occupation, and is associated with a range of physical and psychosocial risks, potentially mediating the effects of a poor corporate climate for worker psychological health (PSC).

Theoretically, the results suggest that both physical and psychosocial mechanisms impact MSD and both must be considered in combination to fully understand the manifestations of MSDs.

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