Small Vessel Disease and Associations with Cerebrospinal Fluid Amyloid, Tau, and Neurodegeneration (ATN) Biomarkers and Cognition in Young Onset Dementia

Background: Small vessel disease (SVD) and Alzheimer’s disease (AD) frequently coexist; however, it remains unclear how they collectively affect cognition. Objective: We investigated associations between SVD and AD biomarkers, namely amyloid, tau, and neurodegeneration (ATN) in young onset dementia (YOD) and explored how SVD and ATN interact to affect cognition. Methods: 80 YOD individuals were recruited from a memory clinic. SVD burden (SVD+) was operationalized as a score >1 on the Staals scale and ATN was measured using cerebrospinal fluid (CSF). Results: SVD+ was associated with lower CSF Aβ 1–42 (B = –0.20, 95% CI: –0.32 to –0.08) and greater neurodegeneration, indexed as hippocampal atrophy (B = –0.24, 95% CI: –0.40 to –0.04). SVD+ was not associated with tau. Cognitive impairment was associated with CSF Aβ 1–42 (B = –0.35, 95% CI: –0.55 to –0.18) but not SVD. Rather, SVD was indirectly associated with cognition via reduced CSF Aβ 1–42 , specifically with global cognition (B = –0.03, 95% CI: –0.09 to –0.01) and memory (B = 0.08, 95% CI: –.01 to .21). SVD was indirectly associated with cognition via increased neurodegeneration in grey matter (Global cognition: B = –0.06, 95% CI: –0.17 to –0.03; Memory: B = 0.05, 95% CI: 0.01 to 0.18) and the hippocampus (Global cognition: B = –0.05, 95% CI: –0.11 to –0.01; Memory: B = 0.06, 95% CI: 0.01 to 0.17). Conclusion: In YOD, SVD burden was associated with AD pathology, namely CSF Aβ 1–42 . SVD indirectly contributed to cognitive impairment via reducing CSF Aβ 1–42 and increasing neurodegeneration.