Alzheimer's disease is not "brain aging": Neuropathological, genetic, and epidemiological human studies

Peter T. Nelson, Elizabeth Head, Frederick A. Schmitt, Paulina R. Davis, Janna H. Neltner, Gregory A. Jicha, Erin L. Abner, Charles D. Smith, Linda J. Van Eldik, Richard J. Kryscio, Stephen W. Scheff

Research output: Contribution to journalReview articlepeer-review

221 Scopus citations

Abstract

Human studies are reviewed concerning whether "aging"-related mechanisms contribute to Alzheimer's disease (AD) pathogenesis. AD is defined by specific neuropathology: neuritic amyloid plaques and neocortical neurofibrillary tangles. AD pathology is driven by genetic factors related not to aging per se, but instead to the amyloid precursor protein (APP). In contrast to genes involved in APP-related mechanisms, there is no firm connection between genes implicated in human "accelerated aging" diseases (progerias) and AD. The epidemiology of AD in advanced age is highly relevant but deceptively challenging to address given the low autopsy rates in most countries. In extreme old age, brain diseases other than AD approximate AD prevalence while the impact of AD pathology appears to peak by age 95 and decline thereafter. Many distinct brain diseases other than AD afflict older human brains and contribute to cognitive impairment. Additional prevalent pathologies include cerebrovascular disease and hippocampal sclerosis, both high-morbidity brain diseases that appear to peak in incidence later than AD chronologically. Because of these common brain diseases of extreme old age, the epidemiology differs between clinical "dementia" and the subset of dementia cases with AD pathology. Additional aging-associated mechanisms for cognitive decline such as diabetes and synapse loss have been linked to AD and these hypotheses are discussed. Criteria are proposed to define an "aging-linked" disease, and AD fails all of these criteria. In conclusion, it may be most fruitful to focus attention on specific pathways involved in AD rather than attributing it to an inevitable consequence of aging.

Original languageEnglish
Pages (from-to)571-587
Number of pages17
JournalActa Neuropathologica
Volume121
Issue number5
DOIs
StatePublished - May 2011

Bibliographical note

Funding Information:
Conflict of interest This study was supported by NIH grants R01 NS061933, K08 NS050110, P30 AG028383, and U01 AG016976.

ASJC Scopus subject areas

  • Pathology and Forensic Medicine
  • Clinical Neurology
  • Cellular and Molecular Neuroscience

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