Predictors of adherence among Alzheimer's disease patients receiving oral therapy

Objectives: Treatment effectiveness depends upon administering medications as prescribed, and adherence is critical for Alzheimer's disease (AD) patients to receive optimal benefit from therapy. The objective of this study was to investigate factors associated with adherence to AD oral medications. Methods: This retrospective claims analysis identified AD patients who initiated oral AD therapy (rivastigmine, donepezil, galantamine, or memantine) between January 1, 2006 and December 31, 2007 from a large US health plan. Patient baseline characteristics were assessed during the 6-month pre-index period; outcomes were assessed during the 1-year post-index period. Pill burden was measured as a count of unique units of medication/day. Adherence was measured by medication possession ratio (MPR), with MPR 80 defined as adherent. Multivariate logistic regression was used to assess how potential covariates affect adherence probability. Results: A total of 3091 AD patients (36 male; mean age 80 [8.25 SD]) were identified. Only 58 of patients were adherent to oral AD medications. Compared to patients <75 years, patients 86 years were likely to be more adherent (OR1.401, p<0.001). Other factors found to be positively associated with the probability of adherence to AD medications were male gender (OR1.175, p<0.05), overall pill burden (OR1.192, p<0.001), and a lower formulary tier status of the AD medication (OR1.332, p<0.001). Conclusion: Among the several variables assessed, being male, ≥86 years of age, having a greater overall daily pill burden, or using a lower formulary tier AD medication was associated with better adherence to oral AD medication in patients diagnosed with AD. The database had no information on caregiver support, medication management interventions, or use of adherence aids that may have affected adherence in this cohort, yet, a substantial proportion of patients (42) remained non-adherent. A better understanding of the causes of non-adherence is necessary, and methods to improve adherence, such as transdermal medications and educational programs, should be considered.