Association of Medication Adherence with HbA1c Control among American Indian Adults with Type 2 Diabetes Using Tribal Health Services

Abstract

<p> </p> <p><strong>OBJECTIVE</strong></p> <p>To examine HbA1c levels and adherence to oral glucose-lowering medication and their association with future HbA1c levels among American Indian adults with type 2 diabetes (T2D) receiving medication at no-cost from a tribal healthcare system. </p> <p><strong>RESEARCH DESIGN AND METHODS</strong></p> <p>Tribal citizens with T2D and who used Choctaw Nation Health Services Authority (CNHSA) and Pharmacies and had HbA1c data during 2017-2018 were included in this study. Medication adherence (proportion of days covered [PDC] ≥ 0.80) was calculated using 2017 CNHSA electronic health record data. </p> <p><strong>RESULTS</strong></p> <p>Of the 74,000 tribal citizens living on tribal lands, 4,560 were eligible. 32% had HbA1c at or below target (≤ 7%); 36% were above target (> 7% to ≤ 9%); 32% were uncontrolled (> 9%) in 2017. Percentage of patients with PDC ≥.80 was 66% for Biguanides, 72% for Sulfonylureas, 75% for DPP-4 inhibitors, and 83% for SGLT-2 inhibitors. The proportion of patients with HbA1c at or below target increased slightly from 32% in 2017 to 42% in 2018. Higher average PDC in 2017 was associated with lower HbA1c levels in 2018 (β=-1.143, p<.001).</p> <p><strong>CONCLUSION</strong></p> <p>Medication adherence was higher than found in previous studies that used self-report methods in American Indian populations, though a smaller proportion of patients had an HbA1c at or below target relative to US adults with T2D. Mediation adherence was associated with improved HbA1c level for most oral glucose-lowering medication classes. Future studies of American Indians should use both longitudinal prescription data from both electronic health record and pharmacy refill data. </p>