A systematic review of barriers to medication adherence in the elderly: looking beyond cost and regimen complexity.

BACKGROUND Medication nonadherence is a common problem among the elderly. OBJECTIVE To conduct a systematic review of the published literature describing potential nonfinancial barriers to medication adherence among the elderly. METHODS The PubMed and PsychINFO databases were searched for articles published in English between January 1998 and January 2010 that (1) described "predictors," "facilitators," or "determinants" of medication adherence or that (2) examined the "relationship" between a specific barrier and adherence for elderly patients (ie, ≥65 years of age) in the United States. A manual search of the reference lists of identified articles and the authors' files and recent review articles was conducted. The search included articles that (1) reviewed specific barriers to medication adherence and did not solely describe nonmodifiable predictors of adherence (eg, demographics, marital status), (2) were not interventions designed to address adherence, (3) defined adherence or compliance and specified its method of measurement, and (4) involved US participants only. Nonsystematic reviews were excluded, as were studies that focused specifically on people who were homeless or substance abusers, or patients with psychotic disorders, tuberculosis, or HIV infection, because of the unique circumstances that surround medication adherence for each of these populations. RESULTS Nine studies met inclusion criteria for this review. Four studies used pharmacy records or claims data to assess adherence, 2 studies used pill count or electronic monitoring, and 3 studies used other methods to assess adherence. Substantial heterogeneity existed among the populations studied as well as among the measures of adherence, barriers addressed, and significant findings. Some potential barriers (ie, factors associated with nonadherence) were identified from the studies, including patient-related factors such as disease-related knowledge, health literacy, and cognitive function; drug-related factors such as adverse effects and polypharmacy; and other factors including the patient-provider relationship and various logistical barriers to obtaining medications. None of the reviewed studies examined primary nonadherence or nonpersistence. CONCLUSION Medication nonadherence in the elderly is not well described in the literature, despite being a major cause of morbidity, and thus it is difficult to draw a systematic conclusion on potential barriers based on the current literature. Future research should focus on standardizing medication adherence measurements among the elderly to gain a better understanding of this important issue.