In work injury prevention, as in other areas of public health, it is crucial to have reliable methods to understand the types of injuries incurred and to track change over time. Such information can be used to target prevention efforts and measure their effectiveness.
Past research in occupational health and safety, including studies conducted at the Institute for Work & Health (IWH), has shown an overall decline in rates of injury in Ontario over the past two decades. But a new IWH study has revealed different patterns running counter to that larger decline.
This study, published in the American Journal of Industrial Medicine in May 2024 (doi:10.1002/ajim.23614), found that although rates of work injuries requiring an emergency department visit declined overall, rates of very severe injuries have not. They remained stable among men and increased among women.
According to the study, over a 14-year period from 2004 to 2017, an average yearly decline of 3.24 per cent was indeed found for mild injuries among men (called “low severity” injuries in the paper). Over the study time frame, that amounted to an overall decline of 34 per cent in the incidence of these types of injuries. For moderately severe injuries among men, an average yearly decline of 2.30 per cent was found, amounting to 26 per cent fewer moderate severity injuries over 14 years.
However, when it came to very severe injuries (called “high severity” injuries in the paper) among men, no such decline was seen. Among women, the rates of very severe injuries actually increased—by an average of 1.22 per cent a year or 18 per cent over the study period.
The study defined high severity injuries as those that cost the province’s workers’ compensation system more than $3,000 in wage replacement and health-care treatment. They represented 10 per cent of all work-related injuries that required an emergency department visit in 2004. With the parallel decline in the incidence of less severe types of injuries, their proportion of all injuries rose to 13 per cent for men and 14 per cent for women by 2017.
“Health and safety professionals in Ontario’s prevention system know that in general, the frequency of injuries has declined over the last 14 years,” says Dr. Cameron Mustard, IWH adjunct scientist and one of the co-authors of the paper. “But the important contribution of this paper is it shows that the most severe and costly injuries have not followed that general trend.”
The findings from this study, which focused mainly on physical injuries, can help those in injury prevention keep an eye on undercurrents where some types of injuries are on the increase and help target prevention efforts, he adds.
| Type of injuries, by severity | Men | Women |
|---|---|---|
| Low | - 3.24 per cent | - 1.72 per cent |
| Moderate | - 2.30 per cent | - 1.14 per cent |
| High | - 0.80 per cent | + 1.22 per cent |
The study also found increases in injuries related to concussions over the same period. Among men, the rate of concussion rose from 11.6 per 100,000 persons in 2004 to 39.0 per 100,000 persons in 2017 a 10 per cent a year increase. Among women, the rate of concussion rose from 6.0 per 100,000 persons in 2004 to 38.8 per 100,000 persons in 2017—a 16 per cent a year rise. “The rise was so large—and not in keeping with other trends—that it suggests a change in diagnosis or detection may be one of the factors behind the rise,” says IWH Scientist Dr. Avi Biswas and co-author of the study.
How the study was done
The study was based on data from both emergency department records and workers’ compensation claims. Over the study timeframe, there were 1.9 million unscheduled emergency department visits by working-age adults (aged 14 to 65) that were deemed by the attending doctor as work-related. There were also 3.7 million work-related injury claims accepted by the Workplace Safety and Insurance Board (WSIB), whether for lost-time wage replacement or for health-care services. Using information on sex, date of birth, postal code and date of injury and emergency department visit, the research team sought to match both sets of data. They identified a matching WSIB claim for 64 per cent of the emergency department visits in the initial sample, and a matching emergency visit for 29 per cent of the WSIB claims. For the study, the research team used both emergency department visit records that could be matched to a compensation claim and those that could not be matched, resulting in a final sample of nearly 1,637,000 cases.
The research team then sorted the injuries in the sample into one of 10 categories for nature of injury (for example, burn, fracture, and so on) and one of 10 categories for injured body part (for example, hand, shoulder, and so on). Injuries included musculoskeletal disorders and diseases of the eye and skin. The result was a matrix of 100 categories (for example, hand burns, shoulder fractures, and so on). For each of these 100 categories, the research team then calculated an average cost in health-care treatment and wage replacement for days off work. They considered injury categories that cost the WSIB less than $1,000 on average to be low severity, injuries that cost between $1,000 and $2,999 as moderate severity, and those that cost $3,000 or more on average to be high severity. Amounts were not adjusted for inflation.
Finally, to calculate the rates of injuries, the researchers needed a denominator (i.e., the total time people are at work and therefore at risk of a work-related injury). For that, they turned to the Statistics Canada’s Labour Force Survey for statistics on the number of people employed (and the number of hours worked).
In the open-access paper, the IWH researchers also examined the causes of injury. In men, by far the most common causes of less severe injuries were those involving inanimate force (for example, being struck or caught by equipment and machinery); falls were the top cause of high severity injuries. In women, inanimate mechanical force was also the main cause of low severity injuries; overexertion was the top cause of moderate severity injuries and falls were the top cause of high severity injuries.
Over the 14-year period, all causes of work-related injury except animate mechanical force (for example, being unintentionally hit or struck by another person) saw a decline among men, though these types of injuries represented a very small proportion of injuries among men. In women, animate mechanical force and assault were two categories that saw an increase across low, moderate and high severity injuries—though these also account for a very small proportion of injuries among women.
“The annual increase in severe injuries among women, which we found in this study, may be due to several factors,” says Biswas. “One may be the growth of service jobs, where women are predominantly employed. Another may be the exposure to workplace violence, which appears related to the rise of injuries from animate mechanical forces and assault.” Other studies on work injury trends, conducted in other North American jurisdictions, “have also found a greater rise in fractures and dislocations among women compared to men,” he adds.