Associations of stable psychological traits with multi-omic subtypes of Alzheimer's dementia

Psychological traits reflecting neuroticism, depressive symptoms, loneliness, and purpose in life are risk factors of AD dementia; however, the underlying biological mechanisms remain largely unknown. Using multi-omic data from the dorsolateral prefrontal cortex of 822 decedents in the Religious Orders Study and Rush Memory and Aging Project, we utilized a previously derived multi-omic brain molecular pseudotime representing molecular distance from no cognitive impairment (NCI) to AD dementia, and three distinct multi-omic brain molecular subtypes of AD dementia. We first confirmed generalizability of pseudotime and subtypes in two independent samples. We then annotated the subtypes, and explored whether they differed by neuropathologic burden, brain morphology or genetic risk, and found that while these indices differentiated all subtypes from NCI they did not differentiate amongst them. Finally, we tested for differential associations between the psychological traits and the subtypes, adjusting first for age, sex, education, and time to death, and then additionally for 9 common AD and Related Dementias pathologies. We found that in fully adjusted models, neuroticism, loneliness and purpose in life remained differentially associated with some AD subtypes relative to NCI. Our results are consistent with a two-stage model in which (i) upstream genetic risk influences overall disease liability, while (ii) intermediary psychological predispositions align more directly with subtype differentiation capturing AD-related heterogeneity not explained by neuropathology or brain atrophy. These results indicate that psychological risk factors may be associated with AD dementia via multi-omic molecular pathways, predominantly informed by metabolomic dysregulation, capturing heterogeneity not explained by neuropathology.