Head Trauma among Severely Injured Motorcyclists: The Impact of Michigan's Motorcycle Helmet Law Modification

Purpose: To evaluate the effects of Michigan’s partial motorcycle helmet law repeal (MPHLR) on helmet use and head injury among crash-involved riders requiring trauma care. Methods: Using probabilistic linkage, adult (≥16-y/o) registry data from 23-trauma centers was cross-linked to state police crash-records for motorcycle crashes occurring 12-months before/after the MPHLR (4/12/11-4/12/13). Rates of head injury and helmet use were compared. Multivariate regression examined the effect of helmet use on head injury. Hospital service utilization was examined. Results: 1,094 patients were identified. No differences were noted before and after MPHLR with regards to rider socio-demographics, alcohol intoxication [BAC>80-g/dL] and crash-related speed limits. Helmet use decreased after MPHLR (91%-vs.-66%, p<0.001), while rates of head injury increased (48%-vs.-57%, p<0.01). Helmet non-use (AOR=2.96) and alcohol intoxication (AOR=3.10) both increased the odds of a head injury among trauma center patients. After adjusting for socio-demographics, unhelmeted riders were more likely intoxicated (AOR=2.51), traveling in a lower speed limit zone (AOR=0.97), Medicaid/self-pay (AOR=1.56) and in the post-MPHLR cohort (AOR=5.60). Unhelmeted riders also had higher utilization of hospital services, including ICU admission (39%-vs-24%, p<0.001) and ventilator care (28%-vs-17%, p<0.001). Conclusions: MPHLR has led to a 27% decline in helmet use and an 18% increase in head injury rates among crash-involved riders requiring trauma care. Helmet non-use was found to triple the odds of a head injury and significantly increased hospital service utilization in this patient population. Until repeals are reversed, innovative strategies to increase helmet use should be explored to prevent negative health outcomes and added medical costs.