Longitudinal Analysis of Objective and Self-Reported Cognitive Functions in Individuals with Subjective Cognitive Decline.

Abstract

Introduction: Subjective cognitive decline (SCD) is considered a preclinical manifestation of Alzheimer's disease (AD). Recent research suggests that subtle cognitive changes in SCD are linked to an increased risk of clinical decline. This study investigates the longitudinal trajectories of both objective and self-reported cognitive functions in individuals with SCD, with a focus on the impact of subtle cognitive impairment (SCI).

Methods: A total of 107 individuals with SCD, with at least two annual follow-ups, were included in this study. We analyzed the trajectories of both objective and subjective cognitive functions, assessed changes in medial temporal lobe regional volumes, and compared baseline AD biomarkers between SCD individuals with SCI (n = 22, SCI group) and without SCI (n = 85).

Results: SCD individuals with SCI showed a faster decline in objective cognitive function over time compared to those without SCI, who exhibited cognitive improvement. Self-reported cognitive complaints showed no differences between groups at baseline or in annual changes over time. The SCI group had lower baseline entorhinal cortical volumes and greater volume reductions over time and also exhibited more abnormalities in AD biomarkers, including higher amyloid PET positivity, a lower Aβ 42/40 ratio, and elevated p-tau181.

Conclusion: SCI status in SCD individuals is associated with significant cognitive decline, along with more abnormal AD biomarkers. These findings suggest that early identification of SCI status in individuals with SCD may improve the prediction of cognitive decline. However, self-reported cognitive complaints may have a limited role in monitoring clinical changes in SCD.