Illness and treatment perceptions are vital for people self-managing co-morbid conditions with associated cardiovascular disease, such as type 2 diabetes (T2D). However, perceptions of a co-morbid condition and the use of multiple medicines have yet to be researched. This study investigated the illness and treatment perceptions of people with co-morbid T2D. The Brief Illness Perception Questionnaire (repeated for T2D, hypertension, and hyperlipidemia) and the Beliefs about Medicines Questionnaire Specific Concerns Scales (repeated for Oral hypoglycemic agents, anti-hypertensive medicines, and statins) were sent to 480 people managing co-morbid T2D. Data on the number of medicines prescribed were collected from medical records. Significantly different perceptions were found across the illnesses. The strongest effect was for personal control; the greatest control reported for T2D. Illness perceptions of T2D differed significantly from perceptions about hyperlipidemia. Furthermore, illness perceptions of T2D also differed from perceptions of hypertension with the exception of perceptions of illness severity. Hypertension and hyperlipidemia shared similar perceptions about comprehensibility, concerns, personal control, and timeline. Significant differences were found for beliefs about treatment necessity, but no difference was found for treatment concerns. 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. Co-morbid illness and treatment perceptions are complex, often vary between illnesses, and can be influenced by the number of medicines prescribed. Further research should investigate relationships between co-morbid illness and treatment perception structures and self-management practices.
Keywords: co-morbidity; illness perceptions; increasing numbers of medicines; polypharmacy; treatment perceptions.