Neuropsychological differences in Alzheimer's disease depending on the age of onset

Early-onset Alzheimer's disease (EOAD) has been defined as a dementia due to AD presenting before the arbitrarily established age of 65 (as opposed to late-onset Alzheimer's disease or LOAD). There is still little research about other age sub-groups, the use of so-called senile dementia has been banished, usually including it within the late-onset Alzheimer's dementia. To the extent of our knowledge, there are no studies comparing the neuropsychological features of very-late-onset patients with early and late-onset ones. We retrospectively selected 359 patients with a diagnosis of probable AD dementia. We subdivided patients into three groups attending to the age of onset of the disease: early-onset AD (EOAD; younger than 65 years old), late-onset AD (LOAD; between 65 and 80) and very-late-onset AD (VLOAD; defined here as onset age older than 80), and then we compared their neuropsychological results. AD patients with a younger age at onset scored worse on attention, executive function and visuospatial skills, while older-onset patients scored worse in memory tasks and language. Patients with a very-late-onset differed from the late-onset ones in a greater impairment of semantic fluency and naming. Although the point of separation between EOAD and later-onset forms of EA at the age of 65 is an arbitrary one, our study shows that there are significant differences between these groups from a neuropsychological point of view. However, these differences do seem to follow a linear trend with age, rather than representing fundamentally distinct clinical pictures.