Caregiver subjective and physiological markers of stress and patient heart failure severity in family care dyads

Greater family caregiver exposure to uncontrolled patient symptoms is predictive of greater caregiver psychological and physiological stress in dementia and other chronic illnesses, but these phenomena have not been well-studied in heart failure (HF) - a disease with high symptom burden. The purpose of this study was to test the hypothesis that worse patient functional status (as reflected by increasing HF symptoms) would be associated with elevated psychological and physiological stress for the caregiver. This was a secondary analysis of data from 125 HF caregivers in the Caregiver Opportunities for Optimizing Lifestyle (COOL) study. Psychological stress was measured on four dimensions: care-related strain/burden (Oberst Caregiving Burden Scale), depression (Center for Epidemiological Studies Depression Scale), anxiety (State-Trait Anxiety Index), and general stress (Perceived Stress Scale). Physiological stress was measured by markers of HPA axis function (elevated cortisol awakening response CAR), endothelial dysfunction (increased PAI-1), and inflammation (increased IL-6, hsCRP). HF patient functional status was quantified by caregiver assessment of New York Heart Association (NYHA) Class. Generalized linear models were used to test associations between patient NYHA Class and stress (one model per indicator). NYHA Class (ordinal) was backwards difference coded in each model to examine caregiver stress in relation to increasing levels of HF severity. Caregivers were mostly female and in their mid-fifties, with a slight majority of the sample being African American and the patient's spouse. Overall, patient functional status was associated with greater caregiver psychological and physiological stress. In terms of psychological stress, higher NYHA Class was significantly associated with greater caregiver anxiety and general stress, but not with caregiver burden or depression. In terms of physiological stress, higher NYHA Class was associated with elevated markers in all models (elevated CAR and higher IL-6, hsCRP, and PAI-1). Across models, most associations between NYHA Class and stress were present at relatively early stages of functional limitation (i.e. Class II), while others emerged when functional limitations became more severe. To inform timing and mechanisms for much-needed caregiver interventions, research is needed to determine which aspects of HF symptomatology are most stressful for caregivers across the HF trajectory.