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Advisory Committee Chair

Susan Davies

Document Type


Date of Award


Degree Name by School

Doctor of Philosophy (PhD) School of Public Health


Medication adherence is an important component of diabetes management, yet nonadherence is common and has substantial patient and economic costs. In order to achieve meaningful improvements in medication adherence, clinicians and researchers need good ways of both identifying those at risk of nonadherence and ascertaining the specific reasons driving nonadherence in those patients. Current options for self-reported medication adherence are limited in their vulnerability to response bias, which may lead to overestimation of adherence. A measure that assesses perceived barriers to medication adherence may be a useful alternative, as it may identify patients at risk of nonadherence while reducing socially desirable responding that is more likely when patients are directly confronted about their specific medication use. It may also be able to identify barriers leading to specific types of nonadherence. This study assessed the psychometric properties of the Perceived Barriers to Medication Adherence (PBMA) scale and the association between perceived barriers and patient sociodemographic characteristics. Exploratory factor analysis suggested a five-factor solution: Regimen, Access, Benefits and Non-financial Costs, Communication, and Memory. There was preliminary evidence for the reliability and validity of the five PBMA scales. Regarding its responsiveness, the PBMA scales had modest effect sizes, and the changes in the scale scores were statistically significant for four out of five PBMA scales, with the exception being the Access scale. Changes in PBMA scale scores were not associated with change in hemoglobin A1c. For associations between perceived barriers and patient sociodemographic characteristics, age was inversely associated with the Benefits and Non-financial Costs score and the Memory score. Regimen scores differed by gender and education, and Communication scores differed by education, income, and partner status. Men living without a partner reported a significantly higher level of Access barriers than men living with a partner. Perceived barriers were not associated with race or urban/rural status. In conclusion, psychometric evaluation of the PBMA scales and its associations with patient characteristics suggested that it may be a useful alternative to a direct assessment of medication adherence. Additional evaluation of the PBMA scales in different populations are needed to confirm the findings of these studies.

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