Objective: To propose an incidence definition of back injury for epidemiologic studies using health care contacts.
Methods: Medical services, hospitalizations, and workers' compensation data were linked for a longitudinal database of health care contacts among a cohort of heavy-industry workers for trajectory, group-based analysis.
Results: During follow-up, 25.8% of workers had no health care contacts for back injury. Among workers with at least one contact, four trajectories were identified: one with a high probability of back injury during follow-up and three with episodic trajectories of increasing and decreasing probability of back injury.
Conclusions: Workers with no back injury history could be followed for incidence in cohort studies or as controls in case-control designs. Episodic groups could be followed for new episodes, providing they were free of health care contacts for back injury for at least 3 years.
From the School of Population and Public Health (Dr Koehoorn, Dr Teschke); School of Environmental Health, College for Interdisciplinary Studies (Dr Koehoorn, Ms Village, Dr Trask, Dr Teschke); and Centre for Health Services and Policy Research, Faculty of Medicine (Dr Koehoorn, Mr Xu), University of British Columbia, Vancouver, British Columbia, Canada.
This project was governed by a Data Access Agreement between the Researchers and the Ministry of Health-Government of British Columbia and WorkSafeBC (03–032). The project was approved by the Behavioural Research Ethics Board, University of British Columbia (B03-0644).
Address correspondence to: Mieke Koehoorn, School of Population and Public Health, University of British Columbia, 2206 East Mall, Vancouver, British Columbia, Canada V6T 1Z3; E-mail: firstname.lastname@example.org.