Maternal and infant gut microbiome.

Chronic Obstructive Pulmonary Disease (COPD) and diabetes mellitus are a common comorbid combination. They mutually exacerbate each other, leading to a heavy symptom burden and increased risk of re-hospitalization for patients, presenting a significant global public health challenge (, ). With the accelerating aging of the population, the health management of older adults with comorbid COPD and diabetes is becoming increasingly complex, and the focus of their medical care is gradually shifting from acute hospital treatment to long-term community and home-based management (, ). In this context, the “hospital-to-home” transition period constitutes a particularly vulnerable and critical window in the patient’s health trajectory (). Studies indicate that up to 30% of such patients experience adverse health outcomes during this phase, such as acute exacerbations, poor glycemic control, and unplanned rehospitalizations (, ). Illness perception refers to the patient’s personal experience and cognitive representation of the disease, encompassing their understanding and emotional response regarding disease symptoms, causes, consequences, and controllability (). In the context of COPD and diabetes comorbidity, patients often face a complex interplay of experiences such as dyspnea, fatigue, and various metabolic symptoms, making them highly susceptible to developing negative illness perceptions, such as feeling a loss of control, fearing deterioration, and losing confidence in treatment (, ). Concurrently, the World Health Organization’s concept of “intrinsic capacity” provides a novel framework for assessing the overall health reserve of older adults with comorbidities (). It refers to the composite of an individual’s abilities across five domains: cognition, psychology, vitality, sensory, and locomotor (). The physiological stress, environmental changes, and polypharmacy during the transition period can easily lead to a precipitous decline in the intrinsic capacity of older patients, thereby undermining the foundation for independent living and creating a vicious cycle of functional decline and deteriorating health status (, ). Current research on transition management for patients with COPD or diabetes predominantly focuses on single diseases or individual outcomes (e.g., rehospitalization rates), lacking an in-depth exploration of the dynamic evolution and interactive influence between the two core psychological and functional constructs: “illness perception” and “intrinsic capacity.” However, according to the Common-Sense Model of Self-Regulation, an individual’s perception of their illness directly influences their coping behaviors and emotional adaptation, which in turn may accelerate or delay the decline of their physiological function (). Conversely, a decline in intrinsic capacity (e.g., cognitive decline, physical frailty) may also impair the patient’s ability to process disease information and execute self-management, thereby exacerbating their perception of the disease as threatening (, ). This potentially bidirectional, dynamic interaction during the critical transition period is key to understanding the heterogeneity in patient outcomes, yet it has not been adequately illuminated by empirical research.