A study involving 105 people with Alzheimer's disease and 125 healthy older adults has compared cognitive function and brain shrinkage in those aged 60-75 and those aged 80+.
It was found that the association between brain atrophy and cognitive impairment typically found in those with Alzheimer’s disease was less evident in the older group. This is partly because of the level of brain atrophy in healthy controls in that age group — there was less difference between the healthy controls and those with Alzheimer’s. Additionally, when compared to their healthy counterparts, executive function, immediate memory and attention/processing speed were less abnormal in the older group than they were in the younger group.
The finding suggests that mild Alzheimer’s in the very old may go undetected, and emphasize the importance of taking age into account when interpreting test performance and brain measures.
(2011). Distinct profiles of brain and cognitive changes in the very old with Alzheimer disease.
Neurology. 77(8), 713 - 721.