title: Predictors of medication nonadherence among patients with diabetes in Medicare Part D programs: a retrospective cohort study.
abstract: OBJECTIVE
  This study examined the prevalence of nonadherence with oral hypoglycemic agents, antihypertensive drugs (angiotensin-converting enzyme inhibitors [ACEIs] and angiotensin II receptor blockers [ARBs]), and statin medications among Medicare Part D enrollees with diabetes and analyzed the potential demographic and clinical factors that predict medication nonadherence.
  
  
  METHODS
  This was a retrospective cohort study of Medicare Part D enrollees with diabetes from 6 states (Alabama, California, Florida, Mississippi, New York, and Ohio). Adherence was calculated as the proportion of days covered (PDC; number of days with medication on hand/number of days in the specified time interval). A PDC was derived for each of the 3 categories of medications for patients who had at least 1 claim for the same class of medication. A comorbidity measure was created for each beneficiary using the Deyo-adapted Charlson Comorbidity Index (CCI). Associations between nonadherence and patient characteristics including age, sex, race/ethnicity, and Deyo-adapted CCI were examined. Logistic regression models were constructed to identify predictors of nonadherence.
  
  
  RESULTS
  The study included 1,888,682 patients with diabetes. The mean (SD) age was 71.6 (11.6) years, and 59.5% (1,123,220/1,888,682) were female. A total of 66.4% (1,254,538/1,888,682) were white, 16.3% (308,158/1,888,682) were black, and 7.8% (147,498/1,888,682) were Hispanic. Estimated rates of non-adherence for oral hypoglycemic agents, ACEIs/ARBs, and statins were 35.1% (386,666/1,101,533), 41.8% (449,561/1,075,285), and 46.4% (447,106/962,877), respectively. In unadjusted analyses, patients aged <65 years, women, black or Hispanic patients, and patients with higher Deyo-adapted CCI were more likely to be nonadherent to all 3 classes of medications. The results were consistent in multivariate analyses, and all results were statistically significant at P < 0.001.
  
  
  CONCLUSIONS
  In this study of Medicare Part D enrollees with diabetes, patients aged <65 years, women, black or Hispanic patients, and those with higher comorbidity scores were more likely to be nonadherent to medications. Interventions should be developed to improve medication adherence among these subgroups so that patients can achieve the full benefits of prescribed pharmacologic therapies.
authors.affiliation: The University of Mississippi School of Pharmacy, University, Mississippi 38677, USA. yiyang@olemiss.edu
authors.forename: Yi
authors.initials: Y
authors.lastname: Yang
authors.forename: Vennela
authors.initials: V
authors.lastname: Thumula
authors.forename: Patrick F
authors.initials: PF
authors.lastname: Pace
authors.forename: Benjamin F
authors.initials: BF
authors.lastname: Banahan
authors.forename: Noel E
authors.initials: NE
authors.lastname: Wilkin
authors.forename: William B
authors.initials: WB
authors.lastname: Lobb
mesh_terms: D000367:Age Factors; D000368:Aged; D047228:Angiotensin II Type 1 Receptor Blockers / Q000627:therapeutic use; D000806:Angiotensin-Converting Enzyme Inhibitors / Q000627:therapeutic use; D000959:Antihypertensive Agents / Q000627:therapeutic use; D015331:Cohort Studies; D015897:Comorbidity; D003920:Diabetes Mellitus / Q000188:drug therapy* / Q000453:epidemiology; D005006:Ethnicity; D005260:Female; D005431:Florida / Q000453:epidemiology; D005544:Forecasting; D006801:Humans; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors / Q000627:therapeutic use; D007004:Hypoglycemic Agents / Q000627:therapeutic use*; D008297:Male; D054524:Medicare Part D; D008875:Middle Aged; D010349:Patient Compliance / Q000706:statistics & numerical data*; D012189:Retrospective Studies; D012737:Sex Factors; D014481:United States / Q000453:epidemiology
chemical_list: D047228:Angiotensin II Type 1 Receptor Blockers; D000806:Angiotensin-Converting Enzyme Inhibitors; D000959:Antihypertensive Agents; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors; D007004:Hypoglycemic Agents