Purpose in life and blood-based biomarkers of brain health.

OBJECTIVES: Purpose in life is associated consistently with better cognitive outcomes. The association between purpose and neurobiomarkers of brain health has been less robust than the association with cognitive outcomes. This research uses the largest sample to date to test the association between purpose in life and four neurobiomarkers of brain health measured from plasma: The Aβ42/Aβ40 ratio, p-tau181, neurofilament light (NfL), and glial fibrillary acidic protein. We further test whether higher purpose is associated with cognitive resilience against neuropathological burden (i.e., better cognitive performance relative to the amount of neuropathology).

METHODS: Data were from the Health and Retirement Study. Participants (N = 4,193; Mage = 68.87, SD = 10.17) reported on their purpose in life and provided venous blood. Biomarkers were assessed using Quanterix's Simoa platforms. Linear regression tested the association between purpose and the four neurobiomarkers. Residual and interaction-based approaches evaluated cognitive resilience.

RESULTS: Purpose in life was associated with lower NfL accounting for sociodemographic factors (β = -0.06, p < .001). Clinical and behavioral covariates accounted for half of this association, but it persisted (β = -0.03, p = .007). Purpose was unrelated to the other three neurobiomarkers. Purpose in life was associated with greater cognitive resilience when tested with the residual approach (β = 0.12, p < .001) but not the interaction approach (βinteraction = 0.01, p = .372).

DISCUSSION: In the largest sample to date, individuals with more purpose in life had less neuronal injury, as measured with NfL. Purpose was unrelated to other common neurobiomarkers of brain health.