Psychosocial determinants of adherence to oral antidiabetic medication among people with type 2 diabetes

Aims and objectives The aim of this study was to identify the psychosocial determinants of adherence to oral antidiabetic medication, according to the Theory of Planned Behaviour (TPB). Background Appropriate adherence to oral antidiabetic medication contributes to long‐term glycaemic control. However, glycaemic control is often poor in people with type 2 diabetes, mainly due to the poor adherence to oral antidiabetic agents. Design Prospective study with 2 waves of data collection, based on STROBE checklist was conducted. One hundred and fifty‐seven adults with type 2 diabetes, in chronic use of oral antidiabetic agents, composed the sample. At baseline, self‐reported measures of medication adherence (proportion and global evaluation of adherence) and of metabolic control (glycated haemoglobin) of diabetes were obtained. Methods The TPB main constructs (attitude, subjective norm and perceived control) and related beliefs were measured. Adherence and metabolic control measurements were obtained in a two‐month follow‐up (n = 157). Results Attitude and subjective norm, together, explained 30% of the variability in intention; their underlying belief‐based measures (behavioural and normative beliefs) explained 28% of the variability in intention. In addition, intention predicted behaviour at follow‐up. However, when added to the prediction model, past behaviour was the only explanatory factor of adherence behaviour. Conclusion Adherence behaviour to oral antidiabetic medication was predicted by intention, which, in turn, was determined by attitude and subjective norm. In order to promote adherence to oral antidiabetic agents, health professionals should include motivational strategies as well as strategies targeted to attitude and subjective norm when designing interventions. Relevance to clinical practice The nonadherence to antidiabetic medication contributes to lack of control of diabetes and ensuing complications. The comprehension of the factors explaining the variability in medication adherence can inform the design of theory‐based interventions aimed at promoting this behaviour.