Measurement, correlates, and health outcomes of medication adherence among seniors

OBJECTIVE: To provide a comprehensive review of the literature on the measurement, correlates, and health outcomes of medication adherence among community-dwelling older adults. DATA SOURCES: Searches of MEDLINE, PubMed, and International Pharmaceutical Abstracts databases for English-language literature (1966-December 2002) were conducted using one or more of the following terms: elderly, adherence/nonadherence, compliance/noncompliance, medication/drug, methodology/measurement, and hospitalization. STUDY SELECTION AND DATA EXTRACTION: From the above search, studies of medication adherence in community-dwelling seniors were selected for review along with relevant publications from the reference lists of articles identified in the initial database search. DATA SYNTHESIS: Although several methods are available for the assessment of adherence, accurate measurement continues to be difficult. The available evidence suggests that polypharmacy and poor patient-healthcare provider relationships (including the use of multiple providers) may be major determinants of nonadherence among older persons, with the impact of most sociodemographic factors being negligible. There is little consensus regarding other determinants of nonadherence. Relatively few high-quality investigations have examined the associations between nonadherence and subsequent health outcomes. Available data provide some support for increased health risks with nonadherence. However, interventions to improve adherence have seldom demonstrated positive effects on health outcomes. CONCLUSIONS: There are few empirical data to support a simple systematic descriptor of the nonadherent patient. The inconsistencies across studies may be attributable, in part, to the inherent difficulties involved in the measurement of a behavioral risk factor such as nonadherence. Future research in this area would be strengthened by incorporation of detailed assessments of patient-reported reasons for nonadherence, the appropriateness of drug regimens, and the effect of nonadherence on health outcomes.