Traumatic brain injury among two-wheeled motor vehicle riders in Utsunomiya, Japan: a comparison between mopeds and motorcycles.

Purpose: Two-wheeled motor vehicles are dichotomized into mopeds and motorcycles (MCs) based on their engine capacity. While efforts have been made, mostly by European researchers, to evaluate the possible difference in the frequency/severity of riders' traumatic brain injury (TBI) between the two categories, the results have been inconsistent.

Methods: To evaluate whether such differences exist in Japan, a single-center, retrospective observational study was conducted on two-wheeled motor vehicle riders wearing a helmet during high-energy road traffic accident (RTA). Between January 2011 and December 2017, 127 moped and 128 MC helmeted riders involved in RTAs had been treated in our institution.

Results: Moped riders were significantly older than MC riders (50.7 ± 25.0 years vs. 35.1 ± 18.6 years, p = 0.04). The frequency of TBI was significantly higher in moped riders than in MC riders (21.3% vs. 10.9%; p = 0.03). However, the frequency of other bodily injuries did not differ significantly. Among the riders with TBI, neither injury severity nor outcomes differed significantly. Multivariate regression analysis showed that the presence of altered mental status was predictive of TBI (OR 23.398; 95% CI 9.187-59.586; p < 0.001). Moped riders trended to have a higher likelihood of sustaining TBI (OR 2.122; 95% CI 0.870-5.178; p = 0.098).

Conclusions: Mopeds are frequently utilized by elderly in Japan, which may have been causally associated with the higher frequency of TBI in moped riders, while other causes, including the difference in helmet type, may also be involved. This study is limited by its small sample size and retrospective design, and multi-center prospective studies are warranted.