Incidence and age distribution of hospitalized presumptive and possible abusive head trauma of children under 12 months old in Japan.

BACKGROUND: Abusive head trauma (AHT) is the leading cause of fatal maltreatment among young children. The incidence of AHT in Japan, however, remains unknown. This study examined the incidence and distribution of age in months among young children under 12 months old hospitalized with intracranial injury in Japan.

METHODS: We conducted multicenter cross-sectional study for children under 36 months old admitted with intracranial injury to hospitals that employed the Diagnostic Procedure Combination (DPC) payment system between 2010 and 2013. Presumptive and possible AHT were defined by the combination of ICD-10 codes modified from the coding system recommended by the US Centers for Disease Control and Prevention.

RESULTS: The average incidence was 7.2 (95% confidence interval [CI]: 7.18-7.26) for presumptive and 41.7 (95% CI: 41.7-41.8) for possible AHT per 100,000 children less than 12 months old from 2010 to 2013. The distributions of age in months for both presumptive AHT and possible AHT had peaks at around two and eight months.

CONCLUSIONS: This is the first study to report the incidence of hospitalized children with presumptive and possible AHT using population-based data. Further datasets are needed to evaluate the incidence and specific preventive strategies to prevent AHT in infants during the months of highest risk.