Predicting Treatment Adherence among Patients Attending Primary Health Care Clinics: The Utility of the Theory of Planned Behaviour

Abstract

Treatment regimens for conditions such as hypertension and Type II diabetes require strict adherence to medical instructions. Yet, adherence among patients living with chronic medical conditions attending public health clinics is typically low. The present study sought to determine the extent to which the Theory of Planned Behaviour (TPB) was able to significantly explain variance in adherence intentions and behaviour in a sample of 117 formerly disadvantaged South Africans living with diabetes and hypertension in the Western Cape. The results showed that the linear combination of TPB variables — Attitudes, Perceived behavioural control, and Subjective norms — was able to account for 47 per cent of the variance in adherence intentions and 23 per cent of the variance in self-reported adherence behaviour. The addition of the variables Psychological distress and Social support to the two regression models, hypothesised to add predictive power to the TPB, yielded non-significant results. The findings of the study are discussed in the context of applying theoretical models of behaviour developed in the industrially developed world and tested on middle-class subjects to patient samples in developing countries such as South Africa. Our findings suggest that social cognitive models of health behaviour such as the TPB may be useful in predicting treatment adherence but should be used in a critical and cautious manner.