When people discuss Alzheimer’s disease, they usually divide it into two classifications: early-onset Alzheimer’s disease and late-onset Alzheimer’s disease, with a subtype of early-onset called early-onset Familial Alzheimer’s disease (eFAD).

Neurologists believe that early-onset Alzheimer’s disease and late-onset Alzheimer’s disease function similarly, but are differentiated by age of onset. Early-onset Alzheimer’s disease is when symptoms occur before age 65 and late-onset Alzheimer’s disease is when symptoms begin at age 65 and older.

Early-onset Alzheimer’s disease is uncommon and only accounts for about 5-10% of all Alzheimer’s disease cases. eFAD is a rare subgroup of early-onset Alzheimer’s disease. eFAD is known to be linked to genetics and accounts for only about 1% of all cases of Alzheimer’s disease. The three known genes that cause eFAD are: amyloid precursor protein (APP), presenilin-1 (PS1), and presenilin-2 (PS2).

Late-onset Alzheimer’s disease is the most common form of Alzheimer’s disease, with symptoms appearing on or after age 65. Genetics is a risk factor for late-onset Alzheimer’s disease, but not everyone who carries the ApoE-e4 gene will develop late-onset Alzheimer’s disease and some of the people with late-onset Alzheimer’s disease do not have a copy of ApoE-e4.

How common is Alzheimer’s disease?

There are three common variants of the ApoE gene: ApoE-e2, ApoE-e3, and ApoE-e4.

Like all genes, you have two copies of ApoE, one from your mother and one from your father. You received the same variant from each parent, thus you have a “homozygous” genotype for the ApoE gene (e3/e3). If you had received a different variant of the gene from your mother than from your father, then you would have been “heterozygous” for the ApoE gene (e2/e3).

Approximately 73% of the US population does not carry a copy of the ApoE-e4 variant. It is estimated that only about 27% of the total US population carries at least one copy of the ApoE-e4 variant.

Other factors that increase risk of Alzheimer’s disease?

ApoE comes in three forms: ApoE-e2, ApoE-e3, and ApoE-e4. Having a high risk copy of this gene (ApoE-e4) does not guarantee that you will develop Alzheimer’s disease. Likewise, possessing a copy of the lowest risk variant (ApoE-e2) does not mean you won’t develop Alzheimer’s disease. Learning your ApoE -related genetic risk can be paired with your age, gender, medical health and lifestyle habits to help assess your Alzheimer’s disease risk. Knowing your overall risk can help you decide how aggressively you want to address your cognitive health.

Genes we look for Alzheimer’s disease

Alzheimer’s disease risk is also influenced by other genes, other medical conditions, age, gender, and environmental and lifestyle factors, so learning your ApoE-related genetic risk is only one part of an assessment of risk.

Can you prevent Alzheimer’s disease?

Not yet. But there's strong evidence that several factors associated with leading a healthy lifestyle may play a role in reducing your risk of Alzheimer's disease and other types of dementia. However, more research is needed before any of these factors can be considered a proven strategy to prevent Alzheimer's disease.

Population-based studies suggest that factors associated with overall good health may also reduce the risk of dementia and cognitive decline. These factors include regular physical activity, eating a healthy diet and keeping your brain active through lifelong learning.

How is Alzheimer’s disease inherited?

Not yet. But there's strong evidence that several factors associated with leading a healthy lifestyle may play a role in reducing your risk of Alzheimer's disease and other types of dementia. However, more research is needed before any of these factors can be considered a proven strategy to prevent Alzheimer's disease.

Population-based studies suggest that factors associated with overall good health may also reduce the risk of dementia and cognitive decline. These factors include regular physical activity, eating a healthy diet and keeping your brain active through lifelong learning.

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ApoE