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Abstract
Background. Increasing numbers of people are managing co-morbid conditions. Hypertension and hyperlipidaemia are often co-morbid conditions associated with Type 2 Diabetes (T2D). Non-adherence to medicines can arise for those who self-manage the complex regimens typical of co-morbid T2D. No studies have examined the complexities of managing medicines for co-morbid T2D and no measure of adjustment towards complex therapy is available. Also, we do not understand whether perceptions about co-morbid conditions are cohesive or made up of individual components with separate identities for each illness. Method. Modified grounded theory was used to explore the perceptions expressed by 19 people managing multiple medicines for T2D and cardiovascular disease (CVD). A cross-sectional study of 480 people managing T2D was undertaken. The aim was to assess variability in non-adherence across medicines, treatment perceptions across medicines and illness perceptions for T2D, hypertension and hyperlipidaemia. The effect that the number of medicines had on non-adherence, treatment beliefs and illness beliefs was also assessed. A questionnaire was developed to assess adjustment to complex therapy and the effect of this new measure on non-adherence, treatment beliefs and illness beliefs. Findings. The interviews revealed that people prescribed multiple medicines hold specific beliefs about their illness, beliefs about medicines as a class of treatment and beliefs about their regimen. Also, people prescribed multiple medicines reported varying levels of adherence to T2D and CVD medicines. Variable levels of adherence were thought to reflect variations in beliefs about treatment and illness. The survey assessed variable adherence, treatment perceptions and illness perceptions for T2D and CVD through within-subjects analyses. Unintentional non-adherence, treatment necessity beliefs and all illness perceptions varied between medicines or illnesses. When the number of medicines was taken as a between-subjects factor only intentional non-adherence, treatment necessity beliefs and perceptions of illness timeline were accounted for. However, when the scale designed to assess regimen beliefs was used as a between-subjects factor all treatment beliefs, adherence behaviours, and illness beliefs were accounted for (with the exception of perceptions of illness severity, which was nearing a level of significance). Therefore, regimen beliefs appear to be more predictive of adherence, illness beliefs and treatment beliefs than the number of medicines prescribed. Conclusion. People with T2D have complex perceptions about their illnesses and medicines including the substitution of medicines with behaviour modification. Variable medicine use was reported qualitatively and was found in the quantitative investigation. The new measure of regimen beliefs detected non-adherence, treatment beliefs and illness beliefs (with the exception of illness severity perceptions). However, further development of this scale is necessary. Prescribers should be aware that nonadherence is multi-faceted and can vary between medicines. Variations in treatment necessity beliefs and illness perceptions are also likely.
