Patterns of CT use in Japan, 2014: A nationwide cross-sectional study

To describe CT usage in Japan by age, gender, and region and to clarify the relationship between aging and CT examination rate.

We conducted a cross-sectional study using openly accessible data from the National Database, which includes all Japanese health insurance claim data from 2014. These data are anonymized and publicly available as spreadsheets. Therefore, this study did not require institutional review board approval. We calculated the rate of CT examinations per 1000 population by age, sex, and region with 99% confidence intervals. Pearson correlation coefficients were calculated between CT rate and aging in each region.

We analyzed 28.1 million CT scans, and the rate per 1000 population was 221.5 (99% CI, 221.4-221.6). By age, the corresponding rate for age 0-9 years was 28.9, that for age 10-9 years was 48.6, that for 20-29 years was 52.2, that for 30-39 years was 69.0, that for 40-49 years was 105.9, that for 50-59 years was 177.6, that for 60-69 years was 303.3, that for 70-79 years was 532.5 and that for ≥80 years was 801.5. The rate for male individuals was 233.6 and that for females was 210.0. The CT examination rate was 171.7 and 296.0 in the lowest- and highest-frequency regions, respectively. The average correlation coefficient between the aging rate in each region and the CT examination rate was 0.58 (0.35-0.74, p=0.00002).

In Japan, the CT examination rate per 1000 population was high (third highest in the world). Age may be a factor that increases CT use. Furthermore, because variation in CT examination rates by age, gender, and region were observed, it is necessary to standardize CT utilization.