In some patients who die at very old age, the brain might show the classic pathologic features of Alzheimer's disease even though the patient did not exhibit dementia, according George M. Savva, Ph.D., of the University of Cambridge, and his associates.
The Cognitive Function and Ageing Study (CFAS) “confirms earlier reports of considerable overlap in the burden of neuropathological features of Alzheimer's disease between groups of the oldest old persons with dementia and those without dementia,” said Dr. Savva.
The brain donors were subjects who had participated in the CFAS when they were aged 70–100 years, undergoing periodic evaluations for dementia with the Mini-Mental State Examination, the Geriatric Mental State Examination, and interviews. A subgroup of 426 subjects donated their brains to the study upon their deaths. In all, 243 had a diagnosis of dementia at the time of death; the rest had been determined to be free of dementia.
The prevalence of moderate or severe neuritic plaques and of neurofibrillary tangles rose with increasing age at death, even in those who had not had dementia. In contrast, the prevalence of cortical atrophy corresponded with dementia diagnoses, the investigators said (N. Engl. J. Med. 2009;360:2302–9).
“Neuropathological validation of the diagnosis of Alzheimer's disease, based on confirmation of the presence of these changes, has a different meaning in the oldest old, because the same burden of pathological features may be found in persons who do not have dementia,” wrote Dr. Savva and his colleagues who reported no relevant conflicts of interest.