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Back Injuries in Heavy Industries: Defining Back Injury Outcomes for Research Purposes (Part A)
RS2002/03-013 (Part A)
Final Report Date: April 2007
| Principal Investigators: | Mieke Koehoorn and Kay Teschke (UBC) |
| Co-Investigators: | Hugh Davies, Paul Demers, Murray Hodgson (UBC); Peter Johnson (University of Washington) |
For more information about this project, please contact Dr. Mieke Koehoorn or Dr. Kay Teschke, or visit the UBC Back Study website.
Issue
Occupational back injuries are very common in B.C., and they are also very costly due to lost workdays, compensation claims, and health care costs. Many research studies, compensation systems and stakeholders have traditionally viewed back injuries as an acute injury, brought on by a specific event. However, more recent research has suggested that back injuries could be a more chronic or episodic (having a number of related episodes) condition. In order to develop new ways to define back injuries and back injury patterns, this study examined data on the health care contacts of a large group of B.C. workers in five heavy industries (forestry, wood and paper products, warehousing, transportation, construction) over a ten year period.
Key findings
- This study developed a way to define a new back injury, as well as methods for measuring patterns of back injury over time that can be used in future research.
- The researchers distinguished five different patterns of back injury in the study population over the ten year period:
- A group with no back related health care contacts (22.9%)
- A group that had a consistent high probability of back-related health care contacts throughout the 10 year period (26.4%)
- Three groups with episodes of back-related health care contacts (e.g., decreasing or increasing patterns over time)
- The identification of these groups will be useful for future research on occupational back injury
Objectives
- To define new onset back injury episodes for use in occupational studies of the causes of back injury.
Methods
The researchers obtained three types of health data through the British Columbia Linked Health Database (BCLHD). This included workers’ compensation claims, hospital discharge records (including day procedures/surgeries), and medical services outpatient visits to general practitioners, specialists, and other practitioners (e.g. chiropractors and physiotherapists). The merged data set was provided to the research team with all identifying information removed. The project was approved by the University of British Columbia Behavioural Research Ethics Board.
The study sample included 116,268 workers living in B.C. who were employed in one of the five target industries in 2001. The sample excluded workers whose employer did not pay their health premium in 2001 and individuals with less than 10 years of continuous follow-up between 1992 and 2001.
A trajectory analysis and other statistical procedures were conducted to identify distinct patterns of back injury related health care contacts over the ten year period.
Results
This study provides a definition of a new back injury, and identifies a number of distinct patterns of back injury among a group of workers employed in heavy industries.
Five distinct patterns of back injury were identified:
- A group (22.9% of study population) with no back-related (diagnosed) health care contacts
- A group (26.4%) with a consistent high probability of back-related health care contacts throughout the 10-year study period
- Three groups with changing patterns (e.g., increasing and decreasing) of back-related health care contacts over time
Based on the findings, a back injury episode was defined by a minimum of two outpatient visits per year. Separate back injury episodes (incidence) were defined by a three year gap with no back injury related health care contacts. Individuals with chronic back injury (prevalence) were defined by a minimum of four back injury related health care contacts per year with no gaps in contacts from year to year. These definitions can be used in future research studies.
Conclusions
The results suggest that workers experience different patterns of back injury over time.
Based on the analysis of these patterns over the ten year period, definitions of chronic and new-onset back injury were developed and are available for use in future occupational research studies.
The different groups identified by this research will be useful for other researchers engaged in studies of occupational back injury. The group that remained injury-free could be followed for future back injury, or could serve as a control group against which to compare other workers. Those experiencing changing patterns of back symptoms could serve as a population experiencing new back injuries in future studies, providing that they remain injury free for at least three years.
Future directions
This study was a part of Phase One of a research program to study the causes of back injuries in heavy industries and to test ways to reduce them. Phase One, which included this study as well as the study entitled Back injuries in Heavy Industries: Risk Factor Exposure Assessment addressed two persistent methodological problems in back injury epidemiology: the difficulty of defining and identifying new cases of back injury, and the difficulty of measuring exposures for large scale epidemiological studies. Phase Two will investigate the relative importance of many different risk factors and their interactions in the development and progression of new onset and chronic back injuries in heavy industry. Phase Three will be a randomized workplace trial of the effectiveness of various control measures to reduce the risk of work-related back injuries.
Publications and Presentations
Koehoorn M, Teschke K, Village J, Trask C, Xu F. Presentation: Back Injury Trajectories among a Cohort of Heavy Industry Workers in British Columbia.
EPICOH2007: 19th International Conference on Epidemiology in Occupational Health. Banff, Canada: October 9-12, 2007.