A historical cohort study of glycemic control in patients with concurrent type 2 diabetes and substance use disorder treated in a primary care setting.

BACKGROUND: Substance use disorder (SUD) is a known barrier to patient-self-management, which can hinder efforts to achieve treatment goals in type 2 diabetes (T2D) when the conditions coexist.

OBJECTIVE: Identify the association between SUD and glycemic control in patients with T2D treated in a primary care setting.

METHODS: This retrospective cohort study included patients with T2D treated by providers at family medicine clinics at an academic medical center and its affiliated regional sites from January 2014 to October 2019. Study index date was the first A1c recorded when T2D and SUD diagnoses had both been documented in the medical record. Glycemic control, measured by hemoglobin A1c (A1c), was identified at baseline and over a 12-month follow-up period and was compared between SUD and non-SUD patients.

RESULTS: Of 9568 included patients with T2D, 468 (4.9%) had a SUD diagnosis. In 237 SUD and 4334 non-SUD patients with A1c data, mean (SD) baseline A1c was 8.2% (2.5) and 7.9% (2.1), respectively (P = 0.043). A1c reduction was statistically greater in SUD patients than non-SUD patients (-0.31% versus -0.06%, respectively; P = 0.015), although the clinical significance is modest. In a multivariable linear regression analysis, follow-up A1c was lower in the SUD versus non-SUD patients (coefficient -0.184, 95% CI -0.358, -0.010; P = 0.038).

CONCLUSIONS: Patients with T2D and SUD had higher baseline A1c but this difference was minimized over a 12-month follow-up period. Additional research is warranted to determine long-term glycemic control and barriers to attaining and maintaining glycemic control in patients with T2D and SUD.