Implicit and Explicit Attitudes Toward Antihypertensive Medications Explain Variation in Pharmacy Refill and Self-Reported Adherence Beyond Traditional Risk Factors: Potential Novel Mechanism Underlying Adherence.

Background In pursuit of novel mechanisms underlying persistent low medication adherence rates, we assessed contributions of implicit and explicit attitudes, beyond traditional risk factors, in explaining variation in objective and subjective antihypertensive medication adherence. Methods and Results Implicit and explicit attitudes were assessed using the difference scores from the computer-based Single Category Implicit Association Test and the subscales of the Beliefs about Medicines Questionnaire, respectively. Antihypertensive medication adherence was measured using pharmacy refill proportion of days covered (PDC: mean PDC, low PDC <0.8) and the self-report 4-item Krousel-Wood Medication Adherence Scale (K-Wood-MAS-4: mean K-Wood-MAS-4, low adherence via K-Wood-MAS-4 ≥1). Hierarchical logistic and linear regression models controlled for traditional risk factors including social determinants of health, explicit, and implicit attitudes in a stepwise fashion. Community-dwelling insured participants (n=85: 44.7% female; 20.0% Black; mean age, 62.3 years; 43.5% low PDC, and 31.8% low adherence via K-Wood-MAS-4) had mean (SD) explicit and implicit attitude scores of 7.188 (5.683) and 0.035 (0.334), respectively. Low PDC was inversely associated with more positive explicit (adjusted odds ratio [aOR], 0.87; 95% CI, 0.78-0.98; =0.022) and implicit (aOR, 0.12; 95% CI, 0.02-0.80; =0.029) attitudes, which accounted for an additional 8.6% (=0.016) and 6.5% (=0.029) of variation in low PDC, respectively. Lower mean K-Wood-MAS-4 scores (better adherence) were associated only with more positive explicit attitudes (adjusted β, -0.04; 95% CI, -0.07 to -0.01; =0.026); explicit attitudes explained an additional 5.6% (=0.023) of K-Wood-MAS-4 variance. Conclusions Implicit and explicit attitudes explained significantly more variation in medication adherence beyond traditional risk factors, including social determinants of health, and should be explored as potential mechanisms underlying adherence behavior.