In 2017, the Japan Diabetes Society and Japan Geriatrics Society published the Clinical Practice Guidelines for the Treatment of Diabetes in older adults, marking a major shift in glycaemic management policy for older adults. The guidelines represented a transition from conventional, uniform targets, originally developed for the general adult population, to stratified glycaemic goals tailored to the complex care needs of older patients, including comorbidities and frailty. Although the 2017 guidelines aimed to promote individualised care and reduce adverse events such as severe hypoglycaemia, the real-world impact on patient outcomes, clinical practice and healthcare expenditures has not been evaluated at the national level.

A population-based interrupted time-series analysis will be conducted using data from the National Database of Health Insurance Claims of Japan, which captures nearly all insured healthcare encounters nationwide. This study will include individuals aged ≥65 years with diabetes who received insurance healthcare services between April 2016 and June 2019. Outcomes will be evaluated across three domains: patient outcomes, clinical practice and healthcare expenditures. Specifically, these will include the incidence of severe hypoglycaemia, acute coronary syndrome, hyperglycaemic emergencies such as diabetic ketoacidosis and hyperosmolar hyperglycaemic state, number of antidiabetic prescriptions and total healthcare expenditures. Primary analyses will use generalised linear mixed-effects models assuming Poisson or negative binomial distributions with adjustments for facility-level heterogeneity. Stratified analyses will be performed according to comorbidity burden, frailty status and receipt of relevant healthcare services. Sensitivity analysis will assess the robustness of the results using an alternative definition of severe hypoglycaemia.

This study was approved by the Ethics Committee of the National Centre for Geriatrics and Gerontology (No. 1752), and the need for informed consent was waived owing to the use of anonymised administrative data. These findings will be disseminated through peer-reviewed publications and presentations at international academic conferences.