Incidence of hospitalization for abusive head trauma in Chiba City, Japan.

Backgrounds This study aimed to examine the incidence of AHT admissions by calculating admission rates of AHT cases among infants less than 12 months old in a population-based sample in Chiba city, Chiba Prefecture, Japan. Methods We retrospectively examined medical records of infants admitted to all pediatric secondary and tertiary hospitals in Chiba City between 2011 and 2015. We collected 13 AHT cases, as assessed by hospital-based multidisciplinary Child Protection Teams (CPTs). One experienced pediatric radiologist and two pediatricians evaluated the case histories and Computed Tomography (CT) images of cases to clinically evaluate the case as "strongly" or "moderately" suspected AHT. Results The overall incidence per 100,000 person-years was 34.5 cases (95% confidence interval [CI]: 18.4-59.1), of which 13.3 (95% CI: 4.3-31.0) were strongly suspected to be AHT and 21.3 (95% CI: 9.2-41.9) were moderately suspected. There were no statistical differences in CT findings between severe and moderately suspected AHT. Conclusions The incidence of hospitalization of infants with AHT was similar to that reported in population-based studies in other countries.