Influence of the Fukushima Daiichi Nuclear Power Plant Accident on the Use of Computed Tomography in Children with Mild Head Injuries: A Retrospective Cohort Study

Abstract

Background: Although computed tomography (CT) may induce cancer, CT seems to be commonly used in children with mild head injuries in Japan. People in Japan are concerned about radiation exposure and radiation-induced cancer because of the Fukushima Daiichi Nuclear Power Plant accident following the Great East Japan Earthquake and Tsunami on March 11, 2011. This study investigated whether the accident influenced the use of CT in children with mild head injuries. Methods: Using the Japan Medical Data Center database, we identified patients aged 15 years or younger who visited clinics because of mild head injuries from January 1, 2008, to December 31, 2013. We excluded patients who were admitted to the hospital or received other medical examinations. Regression discontinuity analysis was used to compare proportions of patients undergoing head CT and having clinically important traumatic brain injury (ciTBI) overlooked before vs. after the accident, adjusting for patient characteristics, secular trends, and clinic effect. Findings: Eligible patients (n = 40,440) were classified as visiting the clinic before (n = 11,659) or after (n = 28,781) the accident. The regression discontinuity analysis showed that the accident was significantly associated with a reduction in the proportion of patients undergoing head CT (odds ratio: 0·73; 95% confidence interval: 0·63-0·86; P < 0·001), whereas the accident was not significantly associated with an increase in cases where ciTBI was overlooked (odds ratio: 0·72; 95% confidence interval: 0·13-4·00; P = 0·710). Similar associations were shown in sensitivity analyses with different bandwidths. Interpretation: The use of CT in children with mild head injuries declined significantly after the Fukushima Daiichi Nuclear Power Plant accident, and there was no increase in ciTBI being overlooked. People's concerns about radiation exposure can reduce unnecessary CT. Funding: Nothing. Declaration of Interest: HY received grant support from the Japanese government. The authors declare that they have no competing interests. Ethical Approval: The study was approved by the Institutional Review Board of the University of Tokyo.