634-P: Poor Adherence to Medication and HbA1c Level Predict Risk of Amputation in Patients with Diabetes Mellitus—Historical Cohort Study Using a Nationwide Claims Database

Poor adherence to medication is a clinically relevant issue closely associated with incidence and deterioration of complications in those with diabetes mellitus (DM). Although an elevated HbA1c level is an established risk factor for lower limb amputation, few studies have evaluated the impact of medication adherence combined with HbA1c levels on lower limb amputation. Thus, we analyzed data from 6,957 patients with DM whose records for oral hypoglycemic agents were available for at least 1 y. Medication adherence was evaluated by the proportion of days covered (PDC), with PDC <70% defined as poor medication adherence. Lower limb amputation was defined by ICD-10 codes and medical procedures. Cox regression model identified variables related to the incidence of amputation. In a mean follow-up of 5.5 y, 9 amputations occurred (0.24/1000 person-years). Mean PDC was 55.7%, with 55.6% of patients non-adherent. Results of multivariate Cox regression analysis showed that HbA1c level and PDC were independently associated with the incidence of amputation (HR (95% CI) 1.19 (0.81-1.76), 0.06 (0.01-0.45)). Compared with PDC ≥70% and HbA1c <9.0%, those with PDC <70% and HbA1c ≥9.0% had an approximately 26 times higher risk for amputation (Figure). This implies the necessity of increasing adherence to medication to prevent lower limb amputation in DM.