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Workplace
Original article
Compensation benefits in a population-based cohort of men and women on long-term disability after musculoskeletal injuries: costs, course, predictors
  1. Valérie Lederer1,2,3,
  2. Michèle Rivard2,3
  1. 1Department of Industrial Relations, University of Quebec in Outaouais, Gatineau, Québec, Canada
  2. 2University of Montreal Public Health Research Institute, Montreal, Québec, Canada
  3. 3Department of Social and Preventive Medicine, University of Montreal, Québec, Canada
  1. Correspondence to Dr V Lederer, Department of Industrial Relations, University of Quebec in Outaouais, CP 1250, succ. Hull, Gatineau, Québec, Canada J8X 3X7; valerie.lederer{at}uqo.ca

Abstract

Objectives The aim of this study is to assess costs, duration and predictors of prolonged compensation benefits by gender in a population characterised by long-term compensation benefits for traumatic or non-traumatic musculoskeletal injuries (MSIs).

Methods This study examined 3 years of data from a register-based provincial cohort including all new allowed long-term claims (≥3 months of wage replacement benefits) related to neck/shoulder/back/trunk/upper-limb MSIs in Quebec, Canada, from 2001 to 2003 (13 073 men and 9032 women). Main outcomes were compensation duration and costs. Analyses were carried out separately for men and women to investigate gender differences. An extended Cox model with Heaviside functions of time was used to account for covariates with time-varying effects.

Results Male workers experienced a longer compensation benefit duration and higher median costs. At the end of follow-up, 3 years postinjury, 12.3% of men and 7.3% of women were still receiving compensation benefits. Effects of certain predictors (e.g., income, injury site or industry) differed markedly between men and women. Age and claim history had time-varying effects in the men's and women's models, respectively.

Conclusions Knowing costs, duration and predictors of long-term compensation claims by gender can help employers, decision makers and rehabilitation specialists to identify at-risk workers and industries to engage them in early intervention and prevention programmes. Tailoring parts of long-term disability prevention and management efforts to men's and women's specific needs, barriers and vulnerable subgroups, could reduce time on benefits among both male and female long-term claimants.

  • Longitudinal study
  • Register-based study
  • Long-term
  • Compensation

https://doi.org/10.1136/oemed-2014-102304

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    What this paper adds

    • This study describes for the first time by gender the costs, duration and predictors of prolonged compensation benefits in a population characterised by long-term compensation benefits.

    • In this population, male workers experienced a longer compensation benefit duration and higher median costs.

    • Effects of certain predictors differed markedly between men and women.

    • Knowing costs, duration and predictors of long-term compensation claims by gender can help employers, compensation agency decision makers and work rehabilitation specialists to identify at-risk workers and industries to engage them in early intervention and prevention programmes.

    • Tailoring parts of long-term disability prevention and management efforts to men and women's specific needs, barriers and vulnerable subgroups could reduce time on benefits among both male and female long-term claimants.

    Background

    Prevention and management of work disability related to musculoskeletal injuries (MSIs) are priorities for Canada and many governments around the world. In Quebec, the compensation budget for work-disabled workers with MSI exceeds $121 million (Canadian) annually.1 ,2 Most workers (90%) resume work rapidly and exit the compensation system within 3 months.1–3 However, the 10% transitioning into long-term work disability (≥3 months) make up a disproportionate 75% of compensation costs.1 ,2

    Long-term work disability associated with MSIs has severe financial and social consequences for injured workers (e.g., loss of autonomy, distress, private expenses), their relatives (e.g., additional housework, reduced income) and businesses (e.g., cost of hiring/training a replacement, pressure on coworkers).4–6 It is also associated with higher use of medical care7 and an increased risk of transition to permanent disability.5 ,8

    Gender differences in compensation benefit costs, duration and predictors of duration have, to our knowledge, never been explored in the subpopulation of workers on long-term disability.9 ,10 Studies indicate women on long-term sickness absence are slightly more likely to transition to permanent disability.8 ,11 Women also face a higher prevalence and incidence of work-related musculoskeletal disorders,12–16 a higher incidence of work disability17 ,18 and a slightly longer duration of work disability.11 ,13 ,15 ,18

    The aim of this study is to assess costs, duration and predictors of prolonged compensation benefits by gender in a population characterised by long-term compensation related to MSIs. Six research questions are addressed: How does the proportion of workers on long-term benefits evolve over the life of the compensation claim in men and women? What is the relationship between length of work disability compensation and cost distributions? What key predictors of time receiving benefits are currently available in Quebec's Occupational Health and Safety Commission (Commission de la santé et de la sécurité au travail (CSST)) administrative worker's compensation database for men and women? Do the effects of these predictors vary over the life of the compensation claim? Does the compensation cost distribution vary by gender? How do the compensation costs vary according to sociodemographic and injury-related predictors uncovered in the predictive analyses?

    Methods

    Design

    This register-based provincial prospective cohort study uses CSST claims data. Claims are coded according to the National Work Injuries Statistics (NWIS) standard Z795. Data were extracted at the CSST's head office. Identifying features were removed for confidentiality.

    Quebec compensation system

    The CSST is the principal provider of worker's compensation in the province of Quebec and covers approximately 93.4% of workers.19 The 6.6% not covered include the self-employed, domestic workers and home caregivers who can acquire personal protection under certain conditions. It is an exclusive provincial fund. The Quebec compensation system is a ‘no-fault’ system (no need to provide proof of fault or employer legal liability for compensation eligibility). All injuries ‘arising out of’ or ‘in the course of employment’ are covered, as are occupational diseases (i.e. diseases contracted ‘out of’ or ‘in the course of’ work and characteristic of that work or directly related to the specific risks of that work). While the treating physician determines the extent of the disability caused by the injury or illness, it is ultimately the CSST that determines whether an injury or illness is work related and whether it is compensable. Theoretically, compensation is equally accessible to men and women. However, studies have shown patterns of discrimination against women.19 ,20 Studies also reveal women in Quebec are less likely to receive adequate monetary compensation or to benefit from postinjury vocational rehabilitation and job retention measures.19

    Definition of MSIs

    An algorithm combining the codes for ‘nature of injury’, ‘injured site’ and ‘event leading to injury’ was used to identify traumatic and non-traumatic MSIs. A definition developed by experts from the CSST, National Public Health Institute of Quebec and Robert-Sauvé Occupational Health and Safety Research Institute to identify non-traumatic disorders in the CSST's databases served as a basis for the algorithm. The definition takes into account the ongoing work of the Canadian Standards Association on the revision of work injury and disease classification.

    Non-traumatic MSIs included musculoskeletal inflammatory or degenerative diagnoses affecting the musculoskeletal structures of the neck/back/trunk/upper limbs attributed to non-traumatic circumstances (repetitive movements, strain, overexertion, vibrations, poor posture, cold exposure), such as intervertebral dysfunctions, specific and non-specific back pain, arthritis, sprain, tendinitis, bursitis and other soft-tissue injuries.

    Traumatic MSIs were identified by reversing the selection to include all musculoskeletal diagnoses caused by traumatic circumstances (fall, car accident, crushing, object strike). Examples include fractures, sprains, tears, specific back pain and other muscle or bone traumas.

    The term ‘injury’ is broadly used throughout this paper whether the symptoms resulted from a sudden traumatic event or were of gradual onset.

    Source and study population

    The source population included the complete cohort of new long-term CSST claims (≥3 months of wage replacement benefits) related to neck, shoulder, back, trunk and upper-limb MSIs in Quebec from 2001 to 2003. Long-term claims represented 10–15% of all MSI claims in the years 2000–2002 in Quebec.21

    The study population was identified in 2 steps. First, 25 307 claims were extracted from the complete CSST database based on the following criteria: claim incurred between 1 January 2001 and 31 December 2003; benefits granted for at least 90 days; coded by the CSST as a new event (not a relapse); with an upper-body injury site; among claimants <60 years old. Data were extracted in July 2008, allowing at least 4.6 years postrecruitment to minimise the risk of missing data due to unsettled administrative details in the claims.

    Second, 22 961 claims were identified as MSIs using the algorithm described above, 1457 claims classified as non-MSIs were excluded, and 889 claims could not be classified because of missing information on ‘nature of injury’ and/or ‘event leading to injury’. After removing claims with missing information (3.7%), 22 105 claims remained.

    Variables and measurements

    Variable selection was largely driven by the information available in the CSST administrative databases, including key predictors identified in the general literature on work disability.22 These variables are considered highly reliable as they serve for the calculation of workers’ compensation and employers’ premiums.

    Outcomes

    The main outcome was time on compensation benefits calculated as the difference between the injury date and the date of the last payment of benefits for a maximum of a 3-year period. Comprehensive compensation costs were also extracted from the CSST databases, including wage replacement benefits (90% of a worker's average net preinjury earnings), medical costs (physiotherapy, drugs, X-rays, laboratory tests, etc.), lump sums for permanent impairment (based on the loss of function of the body), vocational rehabilitation costs (counseling, work assessment, placement assistance, etc.) and other costs (replacement of damaged glasses, translation fees, etc.) incurred within 3 years postinjury. Medical costs do not include standard medical care covered by Canada’s universal healthcare system.

    Sociodemographic variables

    Sex was obtained from each claim record. Age at the time of injury was computed from birth date and converted into 10-year units. Gross annual personal income in Canadian dollars was categorised (≤$14 999; $15–$24 999; $25–$34 999; $35–$44 999; ≥$45 000). Dependents (yes/no) indicates if the worker had a spouse, children <18 and/or financial charge of mentally/physically impaired relatives at the time of injury. Area of residence was determined using a census conversion file from Statistics Canada23 matching claimants’ postal codes to the population size of corresponding areas and dichotomised (large city—population ≥100 000/rural to small city—population <100 000). Industry represents the economic sector of the employer at injury. The 2-digit Classification of Quebec’s economic activities24 extracted from the claim records was aggregated into 8 categories (education/public administration, automotive/manufacturing/steel, service, healthcare, transportation, chemical/processing/electrical/food, construction, agriculture/forest/pulp and paper/mining).

    Injury-related variables

    Type of MSI refers to the traumatic/non-traumatic origin of the injury. Injury sites were categorised into: neck (cervical region), shoulder/trunk/back, upper extremities (hands, wrists, arm, elbow) and multiple sites (multiple upper-body regions). When there is evidence that the injury has led to a permanent physical impairment, loss of body function is established by the CSST as a rate (%) according to specific guidelines and a unique lump sum benefit is paid to compensate the loss of earning. Workers were considered to have a permanent physical impairment (yes/no) if their claim contained records of a permanent impairment rate and lump sum payment.

    Disability-related variable

    Claim history (yes/no) refers to the presence of previous unrelated allowed claim(s) in the CSST databases over the 10-year period preceding the injury under study.

    Analyses of missing claim information

    Of the 22 961 MSI claims, 190 (0.8%) were missing information on the event leading to the injury and 663 (2.9%) on the employer's economic sector, and 3 (<0.001%) on both. There were slightly more data missing among men (4.4% versus 3.1%). Workers with missing data were slightly older, had a slightly higher salary and had a higher proportion of traumatic injuries in men and women. Distribution of other variables (dependents, area of residence, industry, permanent impairment, injury site and claim history) was similar between groups. Overall only a small proportion of claims were excluded due to missing data (3.7%).

    Statistical methods

    Follow-up of the study cohort lasted from 3 months postinjury to 3 years postinjury. The end point was the last day receiving benefits. Claims still open 3 years postinjury were considered right-censored.

    Analyses were carried out separately for men and women to investigate gender differences. Experts in occupational epidemiology have highlighted the advantages of stratification over adjustment strategies to investigate gender-specific determinants.12 ,25

    Men and women's Kaplan-Meier survival functions describing the proportion of workers on long-term benefits in relation to time were estimated and compared (log-rank test). Bivariate analyses compared men and women's distributions of long-term claims according to the sociodemographic, injury and disability characteristics (χ2 tests).

    Multivariate survival models were built following Hosmer and Lemeshow guidelines.26 Injury, disability and sociodemographic variables were tested as predictors for time on benefits. Assumptions of non-informative censoring were found satisfactory. The proportional hazards assumption of the 2 gender-specific models was examined for all variables graphically (log-minus-log plot) and by using time-varying covariates with Heaviside functions of time (split at 1 and 2 years). An extended Cox model with Heaviside functions of time was used to account for covariates with time-varying effects (non-proportional hazards).

    After all main effects had been selected, 3 interactions (age and injury site, age and type of MSI, type of MSI and permanent impairment) suggested by the literature12 and experts in the field were tested and reassessed for proportionality. Continuous variables violating the linearity assumption (verified with graphical methods and statistical tests) were categorised. HRs were estimated with 95% CIs. Goodness-of-fit was assessed plotting dfbetas to detect outliers and influential points.

    Cost analyses assessed the relationships between lengths and costs of long-term MSI claims and between length and distributions of the type of compensation costs for long-term MSI claims. Median costs per claim and total costs were calculated according to sociodemographic and injury characteristics.

    Analyses were conducted using SPSS V.19.0.

    Results

    Of the 22 105 long-term claims studied, 13 073 (59.1%) were filed by men and 9032 (40.9%) by women. Men and women appeared to exit benefits at a similar rate in the first 3–12 months (figure 1). In the second and third year postinjury, the proportion of workers on benefits continued to decrease but at a reduced rate and more slowly in men (log-rank test p value ≤0.0001). Two years postinjury, 17.1% of men and 12.8% of women were still receiving benefits. At the end of follow-up, these proportions were 12.3% in men and 7.3% in women.

    Figure 1
    Figure 1

    Duration curves for time on benefits stratified by gender.

    The distributions of long-term claims differed significantly between men and women (table 1) on most sociodemographic, injury and disability characteristics. In particular, men had higher incomes, more dependents, a higher proportion of trauma and permanent impairments, fewer neck injuries and more past claims. The distribution of industries also differed.

    View this table:
    Table 1

    Distribution of long-term claims by sociodemographic, injury and disability characteristics for men and women (2000–2003)

    Table 2 shows the final multivariate models of predictors of time on benefits for men and women over a period of 3 years postinjury. Factors were included in both final models but they did not always affect men and women similarly. Two factors that showed evidence of non-proportionality (age in men's model and claim history in women's model) were fitted as Heaviside functions of time to take into account their time-varying effects. In men, the age effect was not statistically significant in the first year but grew over the second and third years postinjury. In women, a history of previous compensation claim(s) in the 10 years preinjury was only statistically significant in the third year postinjury. Other predictors, namely income, injury site and industry, had different effects in men and women in terms of either size or directionality. For example, income had a gradient effect among men, those in higher income brackets being more likely to remain on benefits longer. In women, the lowest and highest income brackets were the most at risk of a longer compensation period. The effects of injury type, area of residence and having dependents were similar in size and direction in men and women.

    View this table:
    Table 2

    Final multivariate Cox models of predictors of time on benefits for men and women

    Figure 2 shows that nearly half of the long-term claims (46.9%) exited benefits 3–6 months postinjury, accounting for 18.5% of total costs. On the other end, the small group of claims on benefits for >2 years (15.1%) were responsible for a disproportionally large percentage of the total cost (46.9%).

    Figure 2
    Figure 2

    Relationship between length and cost of long-term musculoskeletal injury claims.

    Online supplementary figure S1 depicts the relationship between length of disability and types of costs incurred by long-term musculoskeletal claimants. It shows that as the duration of compensation increases, the proportion of costs attributed to wage replacement and rehabilitation increases and the proportion of medical and other costs diminishes.

    Online supplementary figure S2 illustrates the distributions of types of costs by gender for long-term MSI claims. It shows a higher proportion of medical costs in women.

    Table 3 lists the median costs per claim and total costs by gender for different sociodemographic and injury-related factors. Median costs in men and women were higher for older workers, workers in the transportation, education/public administration and construction industries, workers with permanent physical impairments and workers with multisite injuries. Total costs, however, were higher among 25–49-year-olds, men in the service and construction industries, women in the service and healthcare industries, men with permanent impairment, women with non-traumatic injuries and men and women with trunk/back/shoulder injuries.

    View this table:
    Table 3

    Costs* by gender for long-term musculoskeletal injury claims according to sociodemographic and injury characteristics

    Discussion

    This study describes for the first time the costs and duration of compensation benefits by gender, as well as their predictors, in a population characterised by long-term compensation.

    Before discussing the results and their implications, it is important to point out that not all workers with MSIs file a claim with the CSST and the CSST does not compensate all claims filed.27–29 A survey in Quebec estimated <20% of workers who lost time at work for a non-traumatic MSI filed a claim.28 Another Canadian study reported that 40% of workers with eligible work-related injuries or illnesses did not file a claim.30

    Also, cessation of benefits is sometimes used as a return-to-work proxy. However, not all workers going off benefits return to work (e.g., some retire or return to school, some are deemed fit to return to work but do not feel able or choose not to do so). Conversely, some workers maintain part of their benefits after returning to work (e.g., for medical treatment or vocational rehabilitation). The differential between indemnity cessation and return to work is especially important in long-term disability. Care should therefore be exercised when comparing claims duration data to work absence data.

    In the present study, 6 out of 10 accepted long-term claims were filed by men. This reflects, in part, differences in occupational exposures31 and in employment rates between men and women (66.8% versus 55.6% in Canada in 2001).32 However, for a variety of legal and social reasons, female workers’ injuries are also more likely to be under-represented in compensation databases.19 First, the proportion of non-traumatic MSIs is higher in women and non-traumatic injuries are less likely to be compensated.19 Second, Quebec women's claims for non-traumatic musculoskeletal disorders are accepted significantly less often than those of men.20 It has also been reported that although domestic and at home caregivers in Quebec (women in great majority) are eligible for optional coverage, <1% actually register for it and pay their own premiums.19 Finally, the proportion of women is higher in some forms of precarious employment, such as temporary work and multiple-job holding,32 in which work injuries are less likely to be reported.33

    Population studies on long-term claimants are scarce and, to our knowledge, only 3 have examined gender differences.8 ,11 ,34 These 3 long-term claimant studies (≥2 months on sickness absence), all conducted in Scandinavian countries, showed a different proportion of women than was found in this study, with respectively 56.1% of female long-term claimants in the Norwegian general working population in the years 1990–1991,11 59.1% among Norwegian workers with compensated MSIs in the year 19978 and 57% in the Swedish general working population in the years 1985–1987.34 These countries have different workers’ compensation systems,35 higher public employment levels (women in majority), higher rates of female employment36 and strong gender equality policies.37

    In the general population of compensated workers with MSIs, women have been shown to experience a slightly longer duration on benefits.18 ,21 The present study shows conversely that in the subgroup of workers on long-term benefits (∼10–15% of all compensated workers), men experience a longer duration on benefits. This result is consistent with the only other study that described durations by gender among long-term claimants,11 which reported an average compensated spell of 170 days in men (SD=111 days) and 159 days in women (SD=106 days) in Norway.

    Long-term work disability is often treated as a homogeneous period in the literature and the effects are assumed to be equivalent across genders. An original aspect of this study is that it shows that the effects of certain factors associated with the duration on benefits varied markedly between men and women, as well as over the life of the compensation claim. For example, an older age at the time of the injury was associated with a longer duration in men and women. This effect was stable over the life of the compensation claim in women, while in men it became statistically significant and increasingly strong 2 and 3 years postinjury. The time-dependent effect of age might be caused by prolonged work disability increasing the difficulty of reintegration into a previously held job. Older unemployed workers face more obstacles and hiring discrimination and are less likely to reintegrate into the workforce.38 In Quebec, injured workers are entitled to their preinjury jobs or an equivalent with the same employer,39 but this right may only be exercised within 1 (workplaces with ≤20 workers) or 2 years (workplaces with >20 workers) postinjury. The fact that the age effect was stable over time in women may indicate that they face age-related hiring difficulties sooner after their injury, either because they choose not to go back to their previous job or because they can not (e.g., in the case of women holding temporary jobs). Annual income had a gradient effect in men, with those with lower incomes being more likely to rapidly exit benefits. In women, the lowest (≤$14 999) and highest income brackets (≥$45 000) were more likely to end benefits faster. Workers with small and large incomes have the most to lose in the compensation process, the former because already-small income is reduced and the latter because wage replacement benefits are subject to an income ceiling. In addition, the concentration of women in some forms of precarious employment such as temporary work and multiple-job holding32 may explain why, among workers in the lowest income bracket, they are more prone than their male counterparts to exit benefits early.

    The industries most at-risk for prolonged duration were the service and construction industries for both genders. Other studies have identified these industries as particularly high risk.40 ,41 Workers in these industries may have more severe injuries and face more difficulties returning to jobs often characterised by heavy manual handling and repetitive tasks. These industries also confront unique challenges in terms of disability management due to high rates of temporary and migrant workers.42 ,43 Although the construction industry was found to be at high risk of prolonged compensation in both groups, the proportion of women working in construction was negligible (0.3% in the study population).

    Gender differences were also noted in the effect of injury site. Neck and trunk/back/shoulder injuries were associated with a longer time on benefits in men compared with upper-extremity injuries. In women, there were no statistically significant differences between injuries at the neck, trunk/back/shoulder and upper extremities. Multisite injuries carried the highest risk in both groups.

    Other factors had similar effects in men and women. For example, having dependents impacted negatively on the duration of compensation in both groups, but the effect was small. An interaction between trauma/non-trauma and the presence of a permanent impairment was also found in both groups. To our knowledge, this interaction had never been tested and has no straightforward explanation. Investigation of whether these four groups differ in terms of recovery expectations and injury perception may be worthwhile. There is strong evidence to support the predictive power of recovery expectations on return-to-work outcomes.22 In the case of non-traumatic disorders, such as non-specific low back pain, the origin of the pain is often impossible to uncover with certainty, and in the absence of decisive clinical tests, it is often diagnosed by exclusion. This can be unsettling to some workers and may, in turn, impede their confidence in their own ability to recover and/or resume work. The perception that one has a serious obscure condition likely to last long may be further enhanced in workers who are told they have a permanent impairment. Regardless of the underlying mechanism, this strong interaction found in both genders warrants further exploration in future studies.

    The small number of claims persisting longer than 2 years accounts disproportionately for the costs. As duration increases, the proportion of costs directed to medical services diminishes and the proportion of costs allocated to wage compensation and rehabilitation substantially increases. These findings are consistent with findings from previous studies conducted in the general population of claimants (short and long term) with low back pain and non-traumatic upper-extremity MSI in the USA.44 ,45

    Costs also differ by gender. The proportion of costs attributed to medical expenses was higher in women, while the proportion of costs associated with lump sums for permanent impairment, rehabilitation and wage replacement was higher in men. Median and total costs were both higher in men. Higher median costs in men reflect their longer compensation durations, but also differences between male and female workforces and differences in compensation. A large part of compensation costs is allocated to wage replacement benefits; however, women in the workforce face salary inequalities in the labour market for the same job or different jobs of the same productivity level.19 In addition, women have on average lower paying jobs and constitute the majority of part-time workers.46 Because the law compensates for pre-injury earning and not future earning capacity, part-time workers are disadvantaged in that they are compensated for a part-time income despite being disabled ‘full-time’.19 Gender discrimination in access to vocational rehabilitation services and job retaining measures may also explain part of the difference in costs.19 ,47

    The median and total costs calculated by gender for different sociodemographic and injury characteristics should help determine where to focus secondary prevention and rehabilitation efforts to reduce the burden of long-term MSI claims. For example, preventing even 1 long-term non-traumatic MSI claim with permanent impairment among male workers could potentially save around $40 072. Looking at total costs, the burden of trunk/back/shoulder injuries and those encountered in the service industry are particularly important for men as well as women. The burden is also particularly heavy for men in the construction and automotive/manufacturing/steel industries and for women in healthcare.

    The strengths of this study include a longitudinal design, a lengthy follow-up period, clear inclusion/exclusion criteria, a large population size allowing the use of gender-sensitive and time-sensitive analyses and minimal missing data on all variables (0–2.9%). Most previous studies targeted the lower back and non-traumatic musculoskeletal disorders. This study encompassed all upper-body MSIs, including those resulting from trauma. This study also captured a variety of compensated costs besides wage replacement benefits.

    Challenges arose from using administrative databases. The scope of predictors available was limited. Variables like social support, psychological distress or physical exposure in the workplace and at home may also have an impact on long-term benefit duration. As discussed above, claim frequencies and costs are likely underestimated, especially for women.19 ,20 The stratification strategy limits the impact of the gender selection bias on the predictive models. In terms of magnitude and costs, however, this suggests the burden associated with long-term MSI claims is even greater than that brought forward using compensation data, especially in women.28 Another consequence of using administrative data is that cost analyses reflect the financial burden on the compensation board only instead of the entire societal cost.48 ,49 Worker's out-of-pocket expenses, costs to recruit and train the injured worker's replacement or costs incurred by relatives in caring for the injured worker are not counted. However, the major costs associated with a compensated long-term MSI are covered by the CSST and were therefore included. Finally, researchers had no control on the quality of the coding by the CSST. The risk of bias is minimised by the fact that all variables used in the study serve either for the calculation of workers’ compensation or employers’ premiums, making them less susceptible to missing data and errors.

    Despite the challenges associated with the use of administrative databases and the subsequent difficulties in estimating the exact burden of long-term MSI-related work disability, these population-level data constitute a powerful tool for policy-relevant research. Their limitations are outweighed by strengths that include comprehensive follow-up, continuous data collection, objective measures and relatively low expense. Information uncovered in this study also has direct implications for practice. It may help compensation agencies, employers, clinicians and other stakeholders to better understand long-term work disability, identify at-risk workers and ultimately reduce the financial burden of those claims. Results suggest rehabilitation efforts and long-term claims management could benefit from taking gender differences into account.

    The results are likely to vary between jurisdictions because of the differences in healthcare systems, workers’ compensation systems, legal systems, public policies, as well as value systems, in particular, with regard to gender roles. Future studies should therefore investigate the extent to which the present findings are generalisable to other jurisdictions beyond Quebec, Canada.

    This study is the first to provide information on gender differences in the length, cost and predictors of long-term MSI-related claims in Canada. It emphasises the need to better understand the population on very long-term disability. It also reinforces the relevance of studying work disability and its risk factors from a gender perspective50 and corroborates the call from other researchers to use stratification strategies to do so.12 ,25

    Acknowledgments

    The authors would like to thank Susan Stock and the Groupe scientifique sur les troubles musculo-squelettiques liés au travail (GS-TMS) experts for assistance in the identification of injury codes relating to non-traumatic MSIs.

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    Supplementary materials

    • Supplementary Data

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    Footnotes

    • Correction notice The section head has been changed since published Online First.

    • Funding The study was supported by the Robert-Sauvé Occupational Health and Safety Research Institute (IRSST—#0099-2820). VL was supported by a Banting and Best Doctoral Research Award from the Canadian Institutes of Health Research and a Doctoral Scholarship from the Robert-Sauvé Occupational Health and Safety Research Institute.

    • Competing interests None.

    • Ethics approval University of Montreal's ethics committee and the CSST's legal office.

    • Provenance and peer review Not commissioned; externally peer reviewed.