Individuals with MCI due to Alzheimer’s disease have subtle problems in one or more cognitive domains plus underlying Alzheimer's pathology. These cognitive problems do not interfere with an individuals’ ability to carry out activities of daily living (ADL).3-5 Early detection of MCI based on subjective cognitive complaints and objective measures of cognitive decline provides an opportunity to diagnose AD early in the disease course before clinical progression to dementia stages.4-6 The World Health Organization (WHO) also supports this paradigm shift towards an earlier AD diagnosis to preserve brain functions as long as possible.13
Approximately 60% of people with MCI due to AD* will progress within 2-3 years to AD dementia14
MCI due to AD
AD Dementia
Individuals in the MCI due to AD stage
Individuals progressed to AD dementia
* n=308 and n=353 people with MCI due to AD according to IWG-2 and NIA-AA criteria, respectively.
Individuals with MCI are at higher risk of progressing to AD dementia.14 MCI can be defined as amnestic (aMCI) or non-amnestic (naMCI). A clinical presentation with memory impairment is characterized as aMCI, whereas individuals with naMCI have impairments in one or more non-memory cognitive domains (e.g., executive function, attention, language, visuospatial function). Both subtypes can be categorized further to single-domain or multiple-domain subtypes.15,16
Individuals with aMCI have a higher likelihood of progressing to AD dementia while naMCI is associated with a higher risk of progression to early-onset AD or to non-AD dementia, such as dementia with Lewy bodies.15-17
The MCI phenotype (aMCI vs. naMCI) and the number of affected domains (single vs. multiple) have important implications for understanding the extent of the underlying AD pathology, disease severity, and likelihood of progression to dementia.16
The detection of MCI signs and symptoms and the differential diagnosis between MCI due to AD and MCI due to other causes is challenging. Consequently, MCI due to AD is often underdiagnosed and overlooked.19 In addition it can be difficult to differentiate MCI from the decline in cognitive abilities seen with normal ageing.20
Therefore, clinical assessment of a patient with a cognitive complaint or informant concern, and further investigation of cognitive domains is essential for physicians to differentiate between normal ageing and other reversible causes of cognitive decline.19,20
Episodic memory and executive function are often the first domains to be impaired in MCI due to AD.21 Although cognition is the core affected feature, mild neuropsychiatric symptoms (NPS) including disturbances in mood, perception,
motivation and behaviour may coexist.22 In some individuals, the primary complaint may be neurobehavioural rather than cognitive.4 NPS are associated with poorer outcomes and greater caregiver burden.22,23
Alzheimer’s Disease3,21,25
Normal Ageing3
Alzheimer’s Disease3,21,25
Normal Ageing3
Alzheimer’s Disease3,21,25
Normal Ageing3
Alzheimer’s Disease3,15,24
Normal Ageing3
Alzheimer’s Disease3,15,24
Normal Ageing3
Alzheimer’s Disease3,15,24
Normal Ageing3
Alzheimer’s Disease3,15,24
Normal Ageing3
Alzheimer’s Disease3,21,25
Normal Ageing3
What’s next
An Alzheimer's diagnosis strategy must combine clinical assessment and biomarker evaluation.
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