title: Psychometric Properties of the Four-Item Morisky Green Levine Medication Adherence Scale among Atherosclerosis Risk in Communities (ARIC) Study Participants.
abstract: OBJECTIVE
  To evaluate the reliability and factorial validity of the four-item Morisky Green Levine Medication Adherence Scale (MGLS) among Atherosclerosis Risk in Communities (ARIC) Study participants.
  
  
  METHODS
  We used the cross-sectional visit 5 data from the ARIC Study to assess the measurement properties of the MGLS. We measured the internal consistency using Cronbach α (where α > 0.70 is considered reliable for group-level measurement), the response frequency, and the inter item correlation. Factor analysis of the MGLS and five other adherence items in the survey was conducted using a polychoric correlation matrix to examine the dimensionality that underlies the MGLS. A vanishing tetrad test was conducted to assess conformity with an effect indicator model.
  
  
  RESULTS
  Among the ARIC visit 5 participants, 6,261 (96%) responded to the MGLS and other questions related to medication adherence in the survey (mean age 76 ± 5 years, 59% women). The Cronbach α for the MGLS was 0.47. The inter-item correlations ranged from 0.11 to 0.26. In the factor analysis of the medication adherence survey questions, a three-factor solution was used. One factor captured the extent of nonadherence, whereas other factors focused on the reasons for nonadherence. The MGLS items spread out across the factors that reflect the extent of as well as the reasons for nonadherence. The results of the vanishing tetrad test indicated that the MGLS consists of items other than effect indicators (P < 0.0001).
  
  
  CONCLUSIONS
  The low reliability together with the factor analysis findings imply that the MGLS may reflect causes as well as the extent of medication adherence. The findings suggest that the MGLS, as presently used, lacks consistency in an elderly population.
authors.affiliation: Department of Health Policy and Management, Gillings School of Global Public Health, the University of North Carolina at Chapel Hill, Chapel Hill, NC, USA. Electronic address: beyhaghi@live.unc.edu.
authors.forename: Hadi
authors.initials: H
authors.lastname: Beyhaghi
authors.affiliation: Department of Health Policy and Management, Gillings School of Global Public Health, the University of North Carolina at Chapel Hill, Chapel Hill, NC, USA; Cecil G. Sheps Center for Health Services Research, the University of North Carolina at Chapel Hill, Chapel Hill, NC, USA.
authors.forename: Bryce B
authors.initials: BB
authors.lastname: Reeve
authors.affiliation: Division of Pharmacotherapy and Experimental Therapeutics, Eshelman School of Pharmacy, the University of North Carolina at Chapel Hill, Chapel Hill, NC, USA.
authors.forename: Jo E
authors.initials: JE
authors.lastname: Rodgers
authors.affiliation: Department of Health Policy and Management, Gillings School of Global Public Health, the University of North Carolina at Chapel Hill, Chapel Hill, NC, USA; Cecil G. Sheps Center for Health Services Research, the University of North Carolina at Chapel Hill, Chapel Hill, NC, USA.
authors.forename: Sally C
authors.initials: SC
authors.lastname: Stearns
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000924:Anticholesteremic Agents / Q000008:administration & dosage; D002317:Cardiovascular Agents / Q000008:administration & dosage; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D007004:Hypoglycemic Agents / Q000008:administration & dosage; D008297:Male; D055118:Medication Adherence / Q000523:psychology*; D008875:Middle Aged; D019338:Polypharmacy; D011594:Psychometrics; D015203:Reproducibility of Results; D012111:Residence Characteristics / Q000706:statistics & numerical data; D057566:Self Report; D012959:Socioeconomic Factors; D011795:Surveys and Questionnaires; D016903:Drug Monitoring
chemical_list: D000924:Anticholesteremic Agents; D002317:Cardiovascular Agents; D007004:Hypoglycemic Agents
keywords: causal indicator; effect indicator; factorial validity; medication adherence; reliability