Time-to-subsequent head injury from sports and recreation activities.

OBJECTIVE To provide population-based risk estimates for sustaining subsequent head injuries (HIs), which occur in sports and recreation (SR). DESIGN Population-based, retrospective, cross-sectional study. SETTING Retrospective review of data from 2 tertiary care and 3 community care emergency departments (EDs) in Edmonton, Alberta, Canada. PATIENTS Individuals younger than 36 years presenting to an ED with an SR-related injury between April 1, 1997, and March 31, 2008. There were 9246 subsequent ED records identified for 8958 patients in the main analysis. MAIN OUTCOME MEASURES Clinically diagnosed HI occurring in SR activities after an index presentation, and the number of days between ED presentations for diagnosed SR-HIs. RESULTS Individuals with 1 and 2 previous SR-related HIs were 2.62 [95% confidence interval (CI), 2.23-3.07] and 5.94 times, respectively, more likely (95% CI, 3.43-10.29) to sustain a subsequent HI than those without a previous HI. The median time-to first HI was 758 days from an initial injury and decreased to 613 days and 303 days for those at risk of second and third SR-related HIs (P < 0.0001). Individuals aged 7 to 13 years were 4.29 times more likely (95% CI, 2.65-6.92) to sustain an HI when presenting with a subsequent SR injury, compared with those aged 30 to 35 years. CONCLUSIONS The odds of sustaining a subsequent HI substantially increase with each successive HI. Time between SR-related HIs shortens as the number of HIs increases. Initial HI may be a key marker to institute high-risk injury prevention measures directed at young persons who present to EDs.