The risk of reinjury in relation to time since first injury: a retrospective population-based study.

BACKGROUND: Trauma victims have been found to be at increased risk for reinjury. Determining the risk factors for reinjury and the temporal pattern of reinjury risk can help with targeting of intervention strategies for preventing trauma recurrence.
METHODS: We performed a retrospective, population-based study in Washington State from 1986 to 2001. Individuals aged 15 to 64 years who were hospitalized for injury were followed for 5 years for hospitalization or death because of reinjury. Poisson regression was used to determine the rate ratio of reinjury, compared with the baseline rate of injury, as a function of time since first injury. Among those injured, proportional hazards regression was used to determine risk factors for reinjury.
RESULTS: The risk of subsequent injury hospitalization or death was elevated 2.59-fold (95% CI: 2.50, 2.68) during the period from 6 months to 5 years after the initial injury. Excluding from analysis the first 6 months after initial injury, the risk of reinjury was highest at 4.10 (95% CI: 3.83, 4.40) between 6 and 12 months after first injury, and then declined to approximately 2.0-fold increased risk above baseline by 30 months. Individuals with self-inflicted injuries were found to be at particularly high risk of reinjury [Hazard Ratio (HR) 2.60 (2.21, 3.05)]. Increasing age, male gender, and alcohol use were also associated with increased reinjury risk. Any injury to the face, spine, and extremities were associated with a decreased risk of reinjury.
CONCLUSIONS: Reinjury risk is highest soon after injury, but persists for at least 5 years after initial injury. Periodic interventions through 5 years after injury, particularly in certain high-risk groups, might have lasting effects on reinjury rates.