What Are the Signs of Preclinical Alzheimer's Disease?

Preclinical Alzheimer's Disease. GSO Images Photographer's Choice/ Getty Images

Preclinical Alzheimer's disease is also known as presymptomatic Alzheimer's, asymptomatic AD and latent AD. Preclinical AD refers to:

1) The time before an individual meets criteria for mild cognitive impairment but has some subtle cognitive decline- that is, a change from his baseline


2) The period where an individual's brain begins to show some changes in its structure as compared to its normal condition, yet the person does not show any cognitive decline.

This is similar to other conditions where an internal change is evident from medical testing but the person feels and appears completely healthy, such as high cholesterol.

The Alzheimer's Association Preclinical Alzheimer’s Disease Workgroup refers to this stage as "not normal, not MCI."

How Long Does the Progression from Preclinical AD to AD Take?

According to the research, this may depend on a number of things. Multiple studies suggest that the follow possibilities which have been correlated with a decreased risk of dementia may influence the rate of progression:

For a limited time, it appears that symptoms of cognitive decline can be delayed by the above factors despite physical changes in the brain, but that at some point, the brain becomes no longer able to compensate for those changes.

This is when symptoms of dementia, such as memory loss and word-finding difficulties, become apparent.

Other factors, such as age, genetics, family history and cardiovascular health, also appear to play a role in determining cognitive functioning.​

Why Is Detecting Preclinical Alzheimer's Disease Important?

Research has shown that the detection of brain changes such as plaque buildup often precedes cognitive decline by more than 10 years. Thus, the hope is that by learning more about how to detect and diagnose preclinical Alzheimer's disease, treatment could begin much earlier and thus preserve cognitive abilities.

Currently, treatment options are very limited; they might slow down the progression of the disease for a time but much of the damage to the brain is already done by the time the dementia is diagnosed.

One of the challenges for science has been to develop a safe, inexpensive and accurate method of evaluating the condition of a person's brain.

Which Changes in the Brain May Signal Preclinical AD?

The Alzheimer's Association Workgroup identified several signs of preclinical AD, including the following:

1) Beta-amyloid accumulation, detectable by PET imaging or cerebrospinal fluid testing

2) Evidence of tau protein in cerebrospinal fluid

3) Grey matter loss in the brain.

4) Hypometabolism (lower energy levels) in areas of the brain typically affected by Alzheimer's such as the hippocampus

5) Subtle cognitive decline not significant enough to meet MCI criteria

Related Reading

Alzheimer's Association. Alzheimer's Association Preclinical Alzheimer’s Disease Workgroup. Criteria for Preclinical Alzheimer's Disease. June 2, 2010. 

Society of Nuclear Medicine and Molecular Imaging. Pre-Alzheimer’s: Metabolic Disorder Found in Cognitively Normal Patients. May 31, 2013. http://www.snmmi.org/NewsPublications/NewsDetail.aspx?ItemNumber=8813

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