Hippocampal grading is sensitive to changes in cognition in early MCI

Abstract

AbstractBackgroundIncreased age and cognitive decline are both associated with changes in the hippocampus. These associations are often measured using hippocampal volume measurements and changes in episodic memory. Some studies have also observed a relationship between hippocampal volume and global cognition. However, these studies often only find associations in progressed stages of cognitive decline. This study examined (1) if hippocampal grading is associated with global cognition in cognitively normal controls (NC), early MCI (eMCI), late (lMCI), and Alzheimer’s disease (AD), and (2) whether these associations differ across diagnostic cohorts.MethodsParticipants for this study were selected from the Alzheimer’s Disease Neuroimaging Initiative. They were included if they completed baseline MRI scans and the Alzheimer’s disease Assessment Scale (ADAS‐13) and Clinical Dementia Rating – Sum of Boxes (CDR‐SB) cognitive tests. A total of 1620 older adults met the inclusion criteria and were included (495 CN, 262 eMCI, 545 lMCI, and 318 AD). Linear regressions examined the association between hippocampal grading and cognitive scores.ResultsLower global cognition (measured by increased ADAS‐13 scores) was associated with hippocampal grading scores in in NC, eMCI, lMCI and AD cohorts. Lower global cognition (measured by increased CDR‐SB scores) was associated with hippocampal grading scores in lMCI and AD, but not in eMCI or NC groups.ConclusionHippocampal grading was associated with changes in global cognition in healthy controls and in disease cohorts when there is sufficient dynamic range in the cognitive test. No correlation between CDR‐SB and NC was found because the NC group only had CDR‐SB scores of 0 and 1. Hippocampal grading may, thus, be a useful measure that is sensitive to progressive changes early in the disease course. Future research should determine if this method is associated with longitudinal changes in cognition.