Mitochondrial health, physical functioning, and daily affect: Bioenergetic mechanisms of dementia caregiver well-being.

OBJECTIVE Chronic stress adversely affects mental and physical well-being. However, health outcomes vary among people experiencing the same stressor. Individual differences in physical and emotional well-being may depend on mitochondrial biology, as energy production is crucial for stress regulation. This study investigated whether mitochondrial respiratory capacity corresponds to individual differences in dementia spousal caregivers' mental and physical health. METHODS Spousal caregivers of individuals with Alzheimer's disease and related dementias (N = 102, mean age = 71, 78% female, 83% White) provided peripheral blood samples and completed self-report questionnaires on quality of life, caregiver burden, and a 7-day affect scale. Multiple and mixed linear regression were used to test the relationship between mitochondrial biology and well-being. RESULTS Spare respiratory capacity (b = 12.76, CI[5.23, 20.28 ], p = .001), maximum respiratory capacity (b = 8.45, CI [4.54, 12.35], p < .0001), and ATP-linked respiration (b = 10.11, CI [5.05, 15.18], p = .0001) were positively associated with physical functioning. At average (b = -2.23, CI [-3.64, -.82], p = .002) and below average (b = -4.96, CI [-7.22, 2.70], p < .0001) levels of spare respiratory capacity, caregiver burden was negatively associated with daily positive affect. At above average levels of spare respiratory capacity, caregiver burden was not associated with positive affect (p = .65). CONCLUSIONS Findings suggest that better mitochondrial health is associated with better psychological and physical health - a pattern consistent with related research. These findings provide some of the earliest evidence that cellular bioenergetics are related to well-being.