Illness perception and self-care in adults with type 1 diabetes mellitus.

Type 1 diabetes (T1D) is a chronic autoimmune disease that requires intensive lifelong self-care, often beginning in childhood or adolescence, with daily demands such as blood glucose monitoring, a balanced diet, and insulin administration. Grounded in the Common-Sense Model of Self-Regulation, this study examined the predictive role of illness perceptions in self-care behaviors among Brazilian adults with T1D. Participants were 107 adults with T1D who completed an online survey including sociodemographic and clinical questions, the Summary of Diabetes Self-Care Activities Questionnaire, and the Brief Illness Perception Questionnaire. The sample was predominantly female, with a mean age of about 31 years and a mean age at diagnosis in adolescence, and showed, on average, moderately adequate glycemic outcomes. Multiple stepwise linear regression analyses indicated that personal control was retained in several exploratory models and was the most consistent predictor of self-care behaviors, including general diet, physical activity, blood glucose monitoring, and medication engagement. Other illness perception dimensions showed behavior-specific associations, such as concern predicting greater engagement in foot care and treatment control contributing to more frequent blood glucose testing, while older age and earlier diagnosis were also related to better care. These findings underscore personal control as a central psychological factor influencing diabetes self-management, reflecting the progressive internalization of responsibility that begins in adolescence and extends into adulthood. Early interventions targeting illness perceptions, particularly personal control, may help strengthen long-term self-care skills and treatment adherence across the lifespan in people with T1D.