[Medical expenses for diabetes care in Japan: Analysis of inter-prefecture differences]

Objectives　Medical expenses for diabetes differ between Japan's 47 prefectures. The medical care expenditure regulation plan aims to reduce regional differences in outpatient medical costs through prevention of severe diabetes, promotion of specific health checkups and specific health guidance, promotion of generic drugs, and proper use of medicines. To achieve this goal, we need to conduct an in-depth analysis of inter-prefecture differences in diabetes care expenses. This study analyzed regional differences in prescription fees for dipeptidyl peptidase-4 (DPP-4) inhibitors and the use of generic sulfonylureas (SUs), glinides, biguanides, α-glucosidase inhibitors (α-GIs), and thiazoline derivatives, using the National Database of Health Insurance Claims and Specific Health Checkups of Japan (NDB). Furthermore, we analyzed regional differences in consultancy fees for dialysis prevention.Methods　We analyzed the 2nd NDB Open Data Japan website of the Ministry of Health, Labor, and Welfare. Pearson's correlation coefficient (r) was used to evaluate the relationship between the medical costs of diabetes and each factor. The correlation coefficient was analyzed with Student's t-test, and a P-value<0.05 was considered statistically significant.Results　Regarding oral hypoglycemic drugs, prefectures with a large number of DPP-4 inhibitors tended to have higher medical costs of diabetes (r=0.40, P=0.0048). Furthermore, such expenses tended to be low in prefectures where the use of generic SU drugs was high (r=-0.43, P=0.0023).Conclusions　In conclusion, the results revealed regional differences in the use of DPP-4 inhibitors and generic SU drugs, which may contribute to the regional differences in medical expenses for diabetes. This study suggests that NDB open data are useful for policy making to reduce regional differences in outpatient medical costs of diabetes.