Association Between HbA1c Levels and Diabetic Peripheral Neuropathy: A Case–Control Study of Patients with Type 2 Diabetes Using Claims Data

BACKGROUND: Evidence on the efficacy of glycemic control for diabetic peripheral neuropathy (DPN) is limited in patients with type 2 diabetes mellitus. Despite the known relationship between hemoglobin A1c (HbA1c) and DPN, the parameters (e.g., mean values or variability) that play an important role have not been elucidated. OBJECTIVE: The objective of this study was to explore factors associated with DPN, including long-term HbA1c parameters, among patients with type 2 diabetes, in a large-scale longitudinal study. METHODS: We conducted a case-control study using a medical claims database. We extracted data of patients with type 2 diabetes and disease records of DPN (indicating that they received treatment for DPN) and those without DPN records (controls), and matched for age, sex, index year, and duration since the first type 2 diabetes record. A logistic regression analysis was performed to explore factors associated with DPN, and a receiver-operating characteristic analysis to estimate the optimal mean HbA1c target. RESULTS: Of 1,792,037 patients with type 2 diabetes, data from 1632 patients (816 per group) were analyzed. The mean HbA1c levels in the 3-year observation period were 7.2 ± 1.0% in the DPN group and 6.9 ± 1.1% in the control group. Elevated 3-year mean HbA1c levels were significantly associated with DPN records (adjusted odds ratio: 1.23, 95% confidence interval 1.06–1.42), while HbA1c variability was not significantly associated. The mean HbA1c levels that discriminated between patients with and without DPN records were 6.5% (unadjusted) and 7.1% (adjusted). CONCLUSIONS: The development or progression of DPN in patients with type 2 diabetes was associated with the 3-year mean HbA1c level in real-world data. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s40801-022-00309-3.