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

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.

Cross-sectional study.

A face-to-face survey was administered to patients at two family medicine clinics in the Midwest, USA.

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.

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.

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).

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.