Mild traumatic brain injury after traffic collisions: a population-based inception cohort study.

OBJECTIVE To study the incidence and claim closure of traffic-related mild traumatic brain injury and the effect of insurance factors. DESIGN Population-based, cohort study of mild traumatic brain injury caused by traffic collisions in Saskatchewan, Canada, between July 1, 1994 and December 31, 1995. On January 1, 1995 the insurance law changed from tort to no fault. SUBJECTS 657 adults, 18 years or older, who hit their head and indicated loss of consciousness or uncertain loss of consciousness and were not hospitalized for more than 2 days. METHODS Subjects entered the cohort on the injury date and exited on the day the insurance claim closed, or on November 1, 1997, when remaining open claims were censored. All 657 subjects answered a baseline questionnaire, and 479 who did not reopen their claim were included in the follow-up. The relationship between claim closure and health was studied in 225 (47%) of these claimants. RESULTS The 6-month incidence dropped from 36/100,000 to 27/100,000 after the insurance change. The median time-to-claim closure dropped from 408 days to 233 days. Prolonged claim closure was associated with both injury and insurance-related factors. Claim closure occurred faster when claimants' health improved. CONCLUSIONS Mild traumatic brain injury incidence and claim closure is affected by both health and insurance-related factors.