High-frequency HbA1c testing among older patients with diabetes in Japan: a longitudinal analysis using medical claims data.

Aims: We aimed to determine the rate of high-frequency HbA1c testing among older Japanese patients (≥ 75 years) with type 2 diabetes who did not have diabetic complications and were not using insulin, and to explore its influencing factors and association with the number of hospital admissions. Methods: A retrospective, longitudinal observation study design based on medical claims data between 2015 and 2020 was adopted. We tracked patients for 3 years to describe the annual rate and determine factors associated with high-frequency HbA1c testing using a hierarchical logistical model. We employed a zero-inflated Poisson model to examine the association between frequency of HbA1c testing and the number of hospitalizations. Results: Among 6594 patients included (mean age 80.4 years), the rates of high-frequency HbA1c testing in the first, second, and third year were 10.2%, 4.8%, and 4.7%, respectively. Follow-up year [odds ratio (OR) = 0.54, 95% confidence interval (CI) = 0.49-0.59];insulin use (OR = 1.63, 95% CI = 1.26-2.11); multi facility for HbA1c testing (OR = 5.51, 95% CI = 4.66-6.51); more than 48 outpatient days per year (OR = 2.13, 95% CI = 1.81-2.51); hospitalizations (OR = 0.66, 95% CI = 0.55-0.79); two or more classes of antidiabetic agents at baseline (OR = 1.32, 95% CI = 1.11-1.56); and dementia at baseline (OR = 0.70, 95% CI = 0.51-0.97) were significantly associated with high-frequency HbA1c testing. No significant association between frequent HbA1c testing and the number of all-cause hospitalizations was found. Conclusions: We revealed a high rate of HbA1c testing among older Japanese patients with type 2 diabetes in ambulatory care and indicated that high-frequency HbA1c testing was more likely to result from the decentralized healthcare system and its structure.