The progression of AD typically spans several stages, and the rate of disease progression varies from person to person.
AD starts with a long asymptomatic stage, called preclinical AD, followed by a symptomatic stage, called mild cognitive impairment (MCI), which eventually progresses to dementia, varying from mild to severe.1 Based on the National Institute on Ageing and Alzheimer’s Association (NIA-AA) Alzheimer’s Disease is defined as a continuous process in both cognitive and biomarker domains rather than as three separate clinical entities. Biomarkers are grouped into those of amyloid beta β (Aβ), pathologic tau, and neurodegeneration (A-T-N).2-4
Today there is greater awareness that AD is a continuum from the preclinical stage to the serious advanced stage. In clinical practice it is extremely useful to refer to the individual stages in order to use the appropriate diagnostic and therapeutic interventions.2
It is recognized that a person with mild cognitive impairment (MCI) is at an increased risk of developing AD. Based on analysis from several cohorts, approximately 60% of subjects with MCI and underlying AD pathology progressed to Alzheimer’s disease-type dementia already within 2-3 years.11 However, current clinical practice often does not recognize a person as having AD until the disease has progressed significantly and dementia is evident.8
Diagnosis of AD at later stages means that the decision-making of the person with AD may be impacted, as behavioural problems and impairments in ADL are already present. A timely diagnosis of MCI due to AD provides HCPs, patients, and care partners with an opportunity to help manage the disease and plan for the future.7
WHAT'S NEXT
It is now recognized that pathological changes of Alzheimer's disease may begin up to 20 years prior to clinical manifestations.