Long-Term Risk Trajectories of Diabetes Differ After Direct-Acting Antiviral and Interferon Therapy in Chronic Hepatitis C: A Real-World Cohort Study

Background/Objectives: Chronic hepatitis C (CHC) infection is an independent risk factor for developing type 2 diabetes mellitus (T2DM). However, it is unknown if antiviral treatment, especially with direct-acting antivirals (DAAs), changes long-term glycemic outcomes. Methods: We conducted a retrospective comparative cohort study of 2489 patients with chronic hepatitis C (CHC) in southern Taiwan between 2005 and 2022 who underwent treatment with either an interferon (IFN)-based or direct-acting antiviral agent (DAA) regimen. Given the distinct treatment eras of IFN and DAA therapies, potential temporal confounding was considered in the analytical design. Patients with existing diabetes or co-infections were excluded. The incidence of new-onset T2DM and longitudinal HbA1c levels were compared between treatment groups over a mean follow-up period of 2.56 years. Results: DAA-treated patients demonstrated a lower crude cumulative incidence of T2DM compared with IFN-treated patients (2.46% vs. 6.91%). However, adjusted analyses did not demonstrate a statistically significant difference between treatment groups. The cumulative risk appeared to plateau after the third year among DAA recipients. Post-therapy, HbA1c levels remained stable in both groups at between 5.5% and 6.5% over as long as five years. Splitting regression revealed that BMI ≥ 30 kg/m², and not treatment type or achieved SVR, was an independent T2DM risk factor. The lowest rates of diabetes incidence were associated with pan-genotypic DAA regimens. Conclusion: DAA-treated patients showed lower crude T2DM incidence than IFN-treated patients; however, this difference was not consistently significant after adjustment for baseline factors. Viral eradication may be associated with favorable metabolic trends; however, the present findings do not establish a causal protective effect against incident T2DM. While increased BMI remained an independent predictor of post-treatment diabetes risk.