The Relationship between Age and Cognitive Subtypes of Alzheimer Syndrome and Related Dementias

We aimed to identify cognitive subgroups of clinically diagnosed Alzheimer's disease (Alzheimer syndrome) and related dementias and test if age of presentation influences patterns of cognitive impairment.

Participants were individuals with mild cognitive impairment (n = 360), vascular mild cognitive impairment (n = 73), Alzheimer syndrome (n = 127), vascular dementia (n = 32), mixed dementia (n = 23), and healthy controls (n = 305). Principal component analysis was run on 25 cognitive variables measured by the Toronto Cognitive Assessment (TorCA). We used hierarchical clustering to identify cognitive subgroups.

We identified seven subgroups. The youngest group was characterized by the lowest scores on the overall TorCA mean, and also on executive function, visuospatial function, and attention, while showing the highest scores on Memory, Orientation, and Language. The oldest clusters had low scores on Memory and Orientation but higher scores on attention. The intermediary clusters had similar age and severity distributions.

The results demonstrate that patterns of cognitive impairment are different in different age groups.