Are illness perceptions, beliefs about medicines and Type D personality associated with medication adherence among thyroid cancer survivors? A study from the population-based PROFILES registry

Objective: To examine self-reported medication adherence and its association with illness perceptions, beliefs about medication and personality among thyroid cancer survivors. Methods: Individuals diagnosed with thyroid cancer between 1990 and 2008, as registered in the Eindhoven Cancer Registry, received our survey; 86% (n = 306) responded. Results: Many patients reported that they never forgot taking their medicines (n = 168; 56%), never altered the dose (n = 258; 88%), never stopped taking them (n = 291; 99%), never decided to miss a dose (n = 284; 97%) and never took less than instructed (n = 286; 97%). Fifty-two percent were classified as nonadherent; of which 14% intentional nonadherent only, 70% were nonintentional nonadherent only and 16% were both intentional and nonintentional nonadherent. Nonadherers were younger, more highly educated, more often employed, had a lower stage at diagnosis, and less often reported ≥2 comorbid conditions than adherers. Furthermore, their illness affected them more emotionally and they more often reported that their life would be impossible without their medicine. Logistic regression models showed that higher age, lower education and lower perceived necessity of medication was associated with better adherence while beliefs about medication, illness perceptions, and personality were not associated with adherence. Conclusions: Despite lifelong dependence on supplement therapy, 52% of thyroid cancer survivors were nonadherent.