Using the extended self-regulatory model to characterise diabetes medication adherence: a cross-sectional study

OBJECTIVES: To cluster the adherence behaviours of patients with type 2 diabetes based on their beliefs in medicines and illness perceptions and examine the psychosocial, clinical and sociodemographic characteristics of patient clusters. DESIGN: Cross-sectional study. SETTING: A face-to-face survey was administered to patients at two family medicine clinics in the Midwest, USA. PARTICIPANTS: One hundred and seventy-four ≥20-year-old, English-speaking adult patients with type 2 diabetes who were prescribed at least one oral diabetes medicine daily were recruited using convenience sampling. PRIMARY AND SECONDARY OUTCOME MEASURES: Beliefs in medicines and illness perceptions were assessed using the Beliefs about Medicines Questionnaire and the Brief Illness Perception Questionnaire, respectively. Self-reported medication adherence was assessed using the Morisky Medication Adherence Scale. Psychosocial correlates of adherence, health literacy and self-efficacy were measured using the Newest Vital Sign and the Self-efficacy for Appropriate Medication Use, respectively. Two-step cluster analysis was used to classify patients. RESULTS: Participants’ mean age was 58.74 (SD=12.84). The majority were women (57.5%). Four clusters were formed (non-adherent clusters: ambivalent and sceptical; adherent clusters: indifferent and accepting). The ambivalent cluster (n=30, 17.2%) included low-adherent patients with high necessity beliefs, high concern beliefs and high illness perceptions. The sceptical cluster (n=53, 30.5%) included low adherent patients with low necessity beliefs but high concern beliefs and high illness perceptions. Both the accepting (n=40, 23.0%) and indifferent (n=51, 29.3%) clusters were composed of patients with high adherence. Significant differences between the ambivalent, sceptical, accepting and indifferent adherent clusters were based on self-efficacy, illness perception domains (treatment control and coherence) and haemoglobin A1c (p<0.01). CONCLUSIONS: Patients with diabetes in specific non-adherent and adherent clusters still have distinct beliefs as well as psychosocial characteristics that may help providers target tailored medication adherence interventions.