Evolving definitions of AD

There have been major developments in research and clinical guidelines for AD since the initial recommendations were published by the US National Institutes of Health and AA in 1984.1 The subsequent updates occurred in 2011 for clinical and 2018 for research guidelines, with the most recent publication in June 2024 on revised criteria for diagnosis and staging of AD.1 2 This latest update caused concerns among clinicians.

In 2011, clinical guidelines were published jointly by the National Institute on Aging and AA (NIA-AA) workgroups.1 In these guidelines, there were three categories under the definition of AD, which was an expansion of the initial 1984 clinical criteria of AD.1 The earliest stage was called preclinical AD which described mostly an asymptomatic phase with presence of biomarkers.1 These biomarkers included amyloid beta proteins which can be detected via either cerebrospinal fluid or PET imaging, and these signified the underlying pathophysiological process hypothesised to potentiate AD.3 The next stage called MCI represents early symptomatic manifestations in AD.1 The third stage was dementia due to AD, which was a revision of the 1984 clinical criteria of AD.1 The 2011 guidelines clearly stated that the detection of preclinical AD was purely for research purposes and did not have any clinical utility.

In 2018, NIA-AA published a Research Framework: Toward a biological definition of Alzheimer’s …