Today, we understand Alzheimer’s disease (AD) to be a continuum. By the time patients show symptoms, the underlying processes of the disease has been at work for up to 20 years.1-3
The AD Continuum
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 before dementia, called mild cognitive impairment (MCI), which finally evolves to dementia, varying from mild to severe.4-7
Preclinical AD
MCI due to AD
Mild Dementia
Moderate Dementia
Severe Dementia
Preclinical AD
duration: Up to 20 years
This is the stage of disease before symptoms become apparent but changes in the brain, such as the abnormal build-up of amyloid beta (a protein), have occurred.1
Mild cognitive impairment (MCI) due to AD
People with MCI show evidence of brain changes with symptoms that may be visible to friends and family, but they do not significantly interfere with daily life.1
Symptoms: A noticeable change in cognition, such as short-term memory loss, problems with wordfinding, or losing track of the day or date.1
Dementia due to AD (mild, moderate, severe)
Includes three steps of disease progression characterised by Alzheimer’s-related brain changes and further decline, including worsening symptoms and functional impairment.1
Mild AD dementia
People are often still able to function independently but need assistance with some activities.1
Dementia due to AD (mild, moderate, severe)
Includes three steps of disease progression characterised by Alzheimer’s-related brain changes and further decline, including worsening symptoms and functional impairment.1
Moderate AD dementia
This is, typically, the longest stage of the disease, when people may have difficulties communicating and experience increased confusion, making it difficult to perform everyday activities.1
Dementia due to AD (mild, moderate, severe)
Includes three steps of disease progression characterised by Alzheimer’s-related brain changes and further decline, including worsening symptoms and functional impairment.1
Severe AD dementia
Patients require constant caregiving as they may lose awareness of their surroundings and experience loss of physical abilities.1
Preclinical AD
MCI due to AD
Mild Dementia
One of the challenges is that the first clinical stage of the disease, called mild cognitive impairment (MCI) due to Alzheimer's Disease, is very often not recognised.8-10 Why is that? This may be due to the difficulty in differentiating early AD symptoms from normal ageing. The first signs of AD are sometimes misinterpreted as being due to normal ageing, with the result that people delay going to a doctor. In addition, certain comorbid conditions, such as depression, hearing impairment, or hypertension, can also impact cognitive and functional abilities, adding to the complexity of making a timely AD diagnosis.8,12
Mild cognitive impairment due to Alzheimer's disease is thus often underdiagnosed and overlooked. This means that an AD diagnosis often occurs late in the disease course after it has advanced significantly and dementia may be evident.8-10
Timely diagnosis of AD is an important first step that provides people with early signs and symptoms the opportunity to plan for the future and better prepare for living with the disease together with their care partners.
Alzheimer’s disease is not part of normal ageing
While age is the strongest known risk factor for cognitive decline, Alzheimer’s disease is not a natural consequence of ageing.1,11 Factors influencing AD development are:12-19
Non-Modifiable Factors
- Ageing: AD risk doubles every 5 years after age 65
- Positive family history
- Female gender
- Genetic predisposition & susceptibility (trisomy 21, rare mutations in dominantly inherited AD genes, and allele ε4 of ApoE gene in sporadic AD)
- Environmental factors
Modifiable Factors
- Lifestyle, such as low physical activity, smoking, unhealthy diet, harmful alcohol use, social isolation, or cognitive inactivity
- Health conditions, such as hypertension, type 2 diabetes, heart disease, depression, dyslipidemia, hyperhomocysteinemia, hearing loss, or obesity
- Others, such as lower levels of education, certain medication, traumatic brain injury, or sleep disturbance
Dementia is NOT part of normal ageing but it refers to a particular group of symptoms caused by neurological disorders1
Alzheimer's disease is the most common cause of dementia among older adults, occurring in 60-80% of cases1
Individuals with mild cognitive impairment may wish to know biological or genetic test information about their probability for developing AD. This information can assist in making life plans.20,21
As we get older, cognitive abilities start to decline, like nearly every part and function of the human body. However, early changes in cognition, such as an increased forgetfulness, thinking more slowly than usual or difficulty multi-tasking, may be caused by the underlying mechanisms of Alzheimer’s disease and not by normal ageing processes.1-3
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Alzheimer’s disease operates out of sight – slowly developing over years causing damage to the brain.