Regional, Geographic, and Ethnic Differences in Medication Adherence Among Adults with Type 2 Diabetes

Ann Pharmacother. 2011 Feb;45(2):169-78. doi: 10.1345/aph.1P442.

Abstract

Background: Medication adherence, a critical component of glycemic control for patients with type 2 diabetes, differs by race/ethnicity. However, few studies have examined regional and rural/urban differences in medication adherence and whether racial/ethnic differences persist after controlling for these differences.

Objective: To examine regional, rural/urban, and racial/ethnic differences in medication adherence in a national sample of veterans with type 2 diabetes.

Methods: We performed a cohort study of a national sample of veterans with diabetes (N = 690,968) receiving prescriptions for insulin or oral hypoglycemic agents in 2002. Patients were followed until death, loss to follow-up, or through December 2006. We calculated the annual medication possession ratio (MPR) for each veteran across 4 groups of medication users: individuals using (1) insulin only, (2) oral hypoglycemic agents only, (3) insulin combined with hypoglycemic agents, and (4) insulin or oral hypoglycemic agents (primary analysis).

Results: In longitudinal models for the primary analysis, adjusting for relevant covariates and time trends, MPR was significantly lower among non-Hispanic blacks (NHBs), Hispanics, and individuals with other/missing/unknown race/ethnicity (6.07%, 1.76%, and 2.83% lower, respectively) relative to non-Hispanic whites (NHWs). MPR was also 2.0% higher in rural versus urban veterans and 1.28% higher in the mid-Atlantic, 2.04% higher in the Midwest, and 0.76% lower in the West, relative to the South. There was a significant race/ethnicity and urban/rural interaction. In NHWs and NHBs, MPR was 1.91% and 2.00% higher, respectively, in rural versus urban veterans; in contrast, in Hispanics, MPR was 1.0% lower in rural veterans relative to urban veterans.

Conclusions: In a national longitudinal cohort of veterans with type 2 diabetes, we found significant regional, rural/urban, and racial/ethnic differences in MPR. Rural/urban residence modified the effect of race/ethnicity on MPR. Recognition of these differences can enable clinicians to better allocate resources and target quality improvement programs.

Keywords: cohort; diabetes mellitus; health disparities; medication adherence.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Administration, Oral
  • Adult
  • Black People
  • Blood Glucose
  • Cohort Studies
  • Diabetes Mellitus, Type 2 / drug therapy*
  • Drug Therapy, Combination
  • Female
  • Hispanic or Latino
  • Humans
  • Hypoglycemic Agents / administration & dosage*
  • Insulin / administration & dosage
  • Male
  • Medication Adherence / ethnology
  • Medication Adherence / statistics & numerical data*
  • Middle Aged
  • Rural Population
  • Urban Population
  • Veterans
  • White People

Substances

  • Blood Glucose
  • Hypoglycemic Agents
  • Insulin