Current Status of Delay in Injectable Therapy among Type 2 Diabetes Mellitus Patients in South Korea: Multicenter Retrospective Study (2015-2021).

Background: We aimed to assess the therapeutic inertia associated with injectable therapies and the factors influencing glycemic control following these therapies in patients with type 2 diabetes mellitus (T2DM) in South Korea.

Methods: This multicenter, retrospective cohort study included 2,598 T2DM patients aged 20 to 75 years from 10 referral medical centers in South Korea. These patients had been treated with three or four oral antidiabetic drugs (OADs) and were subsequently initiated on insulin (n=1,942) or glucagon-like peptide-1 receptor agonists (GLP-1RAs, n=656) between January 2015 and December 2021. We analyzed the time to initiation of injectable therapy, changes in glycated hemoglobin (HbA1c), and associations between clinical factors and glycemic control.

Results: At the time of injectable therapy initiation, the mean HbA1c was 9.54%, with insulin users having a higher HbA1c level (9.79%) than GLP-1RA users (8.70%). The mean time from starting 3 or 4 OADs to initiating injectable therapy was 3.19 years: 53.5% of patients had started injectable therapy after 2 years, and 24.2% started after 5 years. Among insulin users, older age (P= 0.004), higher body mass index (P=0.035), and lower HbA1c levels at insulin initiation (P<0.001) were associated with better glycemic control. Among GLP-1RA users, only the HbA1c level at therapy initiation (P<0.001) was a significant factor.

Conclusion: This study highlighted significant delays in initiating injectable therapies, particularly insulin, in T2DM patients in South Korea. Early initiation of injectable therapy may improve long-term glycemic control in these patients.