title: Unintentional non-adherence to chronic prescription medications: how unintentional is it really?
abstract: BACKGROUND
  Unintentional non-adherence has been characterized as passively inconsistent medication-taking behavior (forgetfulness or carelessness). Our objectives were to: (1) study the prevalence and predictors of unintentional non-adherence; and (2) explore the interrelationship between intentional and unintentional non-adherence in relation to patients' medication beliefs.
  
  
  METHODS
  We conducted a cross-sectional survey of adults with asthma, hypertension, diabetes, hyperlipidemia, osteoporosis, or depression from the Harris Interactive Chronic Illness Panel. The analytic sample for this study included 24,017 adults who self-identified themselves as persistent to prescription medications for their index disease. They answered three questions on unintentional non-adherence (forgot, ran out, being careless), 11 questions on intentional non-adherence, and three multi-item scales assessing perceived need for medication (k = 10), perceived medication concerns (k = 6), and perceived medication affordability (k = 4). Logistic regression was used to model predictors of each unintentional non-adherence behavior. Baron and Kenny's regression approach was used to test the mediational effect of unintentional non-adherence on the relationship between medication beliefs and intentional non-adherence. Bootstrapping was employed to confirm the statistical significance of these results.
  
  
  RESULTS
  For the index disease, 62% forgot to take a medication, 37% had run out of the medication, and 23% were careless about taking the medication. Common multivariate predictors (p < .001) of the three behaviors were: (1) lower perceived need for medications; (2) more medication affordability problems; (3) worse self-rated health; (4) diabetes or osteoporosis (relative to hypertension); and (5) younger age. Unique statistically-significant predictors of the three behaviors were: (a) 'forgot to take medications' - greater concerns about the index medication and male gender; (b) 'run out of medications' - non-white race, asthma, and higher number of total prescription medications; (c) 'being careless' - greater medication concerns. Mediational tests confirmed the hypothesis that the effect of medication beliefs (perceived need, concerns, and affordability) on intentional non-adherence is mediated through unintentional non-adherence.
  
  
  CONCLUSIONS
  For our study sample, unintentional non-adherence does not appear to be random and is predicted by medication beliefs, chronic disease, and sociodemographics. The data suggests that the importance of unintentional non-adherence may lie in its potential prognostic significance for future intentional non-adherence. Health care providers may consider routinely inquiring about unintentional non-adherence in order to proactively address patients' suboptimal medication beliefs before they choose to discontinue therapy all together.
authors.affiliation: U,S, Outcomes Research, Merck & Co,, Inc, 351 North Sumneytown Pike, North Wales, PA 19454, USA. abhijit_gadkari@merck.com
authors.forename: Abhijit S
authors.initials: AS
authors.lastname: Gadkari
authors.forename: Colleen A
authors.initials: CA
authors.lastname: McHorney
mesh_terms: D000328:Adult; D000368:Aged; D001249:Asthma / Q000188:drug therapy / Q000523:psychology; D002908:Chronic Disease / Q000188:drug therapy* / Q000523:psychology; D003430:Cross-Sectional Studies; D003866:Depressive Disorder / Q000188:drug therapy; D003920:Diabetes Mellitus / Q000188:drug therapy; D011307:Drug Prescriptions / Q000706:statistics & numerical data*; D005260:Female; D007722:Health Knowledge, Attitudes, Practice; D006304:Health Status; D006801:Humans; D006973:Hypertension / Q000188:drug therapy; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D010024:Osteoporosis / Q000188:drug therapy; D010349:Patient Compliance / Q000523:psychology* / Q000706:statistics & numerical data; D011237:Predictive Value of Tests; D015995:Prevalence; D018434:Sickness Impact Profile; D012923:Social Class; D011795:Surveys and Questionnaires; D014481:United States