Factors associated with adherence to medication regimens in older primary care patients: the Steel Valley Seniors Survey.

OBJECTIVE: The aim of this study was to explore associations between 2 specific cognitive domains and aspects of medication management among older primary care patients.
METHODS: A sample of patients aged >or=65 years drawn from several small-town primary care practices was carefully characterized by cognitive testing and use of prescription medications. Two primary outcome variables were examined: (1) self-reports of setting up schedules to manage their own medications and (2) overall research assessment of adherence to prescribed medications. Predictor variables included scores on tests of verbal memory (Hopkins Verbal Learning Test) and executive function (Part B of the Trail Making Test); prescription insurance status; number of medications; and dosing frequency, adjusting for age, sex, and level of education. Multiple logistic regression and generalized estimating equation models were used for multivariable analyses.
RESULTS: The analytic sample included 343 patients (238 women, 105 men; mean [SD] age, 77.52 [6.71] years). Higher scores on the verbal memory test were independently associated with successfully setting up a medication schedule, after adjusting for covariates (compared with scores in the <10th percentile, odds ratio [OR] for scores between the 10th and 50th percentiles: 5.02 [95% CI, 2.22-11.33; P < 0.001]; OR for scores in the >50th percentile: 6.52 [95% CI, 2.76-15.42; P < 0.001]). Higher scores on the executive function test were associated with treatment adherence (compared with scores in the <10th percentile, OR for scores between the 10th and 50th percentiles: 3.25 [95% CI, 1.13-9.33; P = 0.03]; OR for scores in the >50th percentile: 4.32 [95% CI, 2.76-15.68; P = 0.02]). Compared with using <or=4 prescription drugs, using >or=5 drugs was also associated with poor adherence (OR: 0.45 [95% CI, 0.21-0.95; P = 0.04]) as measured by research nurses' assessment of adherence.
CONCLUSIONS: In this sample of older patients assessed for medication management, independent cognitive processes were associated with the ability to set up a medication schedule and overall adherence to prescriptions. Better verbal memory functioning was strongly and independently associated with setting up a medication schedule, while better executive functioning was strongly and independently associated with being fully adherent to prescription instructions. Deficits in either cognitive ability could result in medication errors due to nonadherence.