Abstract INTRODUCTION People with subjective cognitive decline (SCD) and cognitive impairment, no dementia (CIND) have higher risks of dementia. This study investigated whether fixel‐based and free‐water (FW) metrics, which examine the white matter (WM) structure, differ in SCD and CIND and their relationships with cognition. METHODS We analyzed cross‐sectional data from 247 participants (median age = 63), separated into three groups: healthy controls (HC), SCD, and CIND. RESULTS HC had lower fiber bundle cross‐section (FbC) in the splenium than SCD. HC had higher FbC in the left cerebellum and higher fiber density in the corpus callosum than CIND, and SCD had higher FbC in the right cerebellum than CIND. CIND had higher FW in the temporal lobe and basal ganglia than HC and exhibited less extensive FW differences with SCD. Fixel‐based and FW metrics associated positively and negatively with cognition, respectively. DISCUSSION Fixel‐based metrics have potential to detect WM changes associated with SCD.
Lee et al. (2026) studied this question.