Featured Article December 10, 2019

Will I get Alzheimer's? The answer could be hiding in your genes

Will I get Alzheimers?

Will I get Alzheimer's? This is a common concern among many. Here, we explain who is at risk and why the answer may be in your genes. 

Alzheimer's disease is the sixth most common cause of death in the US. 

With another person developing the disease every 65 seconds on average, it's something that is likely to affect all of our lives in one way or another.

When faced with such statistics it is inevitable that we all stop to ask ourselves: Will I get Alzheimer's? Am I at risk?

Read on as we take a look at the disease, the risk factors, and how your genes could hold the answer to those questions.

What is Alzheimer's?

Alzheimer's disease is an irreversible brain disorder. It is a progressive condition that causes issues with memory, cognition, and behavior. 

It was first discovered in 1906 by Dr. Alois Alzheimer, a German psychiatrist and neuropathologist. He examined the brain of a woman who had died following symptoms including memory loss, language problems, and altered behavior. He found unusual clumps in her brain, known as amyloid plaques, as well as tangles in her brain fibers that are some of the main features of Alzheimer's disease.

Since this initial discovery, many other complex changes in the brain have been discovered among people suffering from Alzheimer's disease, including the loss of connection between neurons.

What are the symptoms?

The most common early symptom of  Stopping Alzheimer's disease before it erases memories, personalities and lives?Yes, it's possible. Using genomic technologies and specialized mouse models to develop preventative therapies, JAX scientists aim to stop Alzheimer’s before it starts.Alzheimer's disease is probably the most well-known.

Struggling to be able to retain new information is one of the common signs of the onset of the disease. This is more than just struggling to remember someone's name as you get a little older. It is a much more serious memory loss that sufferers may not be able to notice themselves initially.

As well as memory loss, symptoms of Alzheimer's include a decline in other aspects of thinking. This can include struggling to find the right words, being unable to complete familiar tasks, impaired judgment, and even problems with vision and spatial awareness. 

At its most severe, Alzheimer's can cause sudden mood swings, extreme changes in behavior, crippling confusion, and even physical issues such as difficulties speaking, walking, and eating.

What are the risk factors?

Research has shown a number of possible factors that can impact your chances of getting Alzheimer's disease, although none of these are a cause in and of themselves.

Age

Old age is one of the most obvious risk factors. The vast majority of people develop Alzheimer's after the age of 65, and once you reach 65, your risk of getting Alzheimer's doubles every five years. But Alzheimer's doesn't only affect people over 65; it has been known to affect people half that age, although this is much rarer.

Family history

History of Alzheimer's in your family will also increase your risk of getting the disease. The risk increases even more if you have multiple family members who have suffered from the disease.

Whilst this may be due to the hereditary genetic factors we will look at in more depth later, there may be other factors at play. These could include environmental factors that impact both yourself and your family.

If you do have a history of Alzheimer's in your family, don't panic. The increase in risk due to a family history of Alzheimer's is only about 0.6 percent. Age is still a much more important risk factor.

Gender

Gender is another significant risk factor for Alzheimer's disease.

The first discovery of the disease back in 1906 was in a woman, and about twice as many women as men over 65 have Alzheimer's. This may be in part to the fact that women have a longer lifespan or may even possibly be linked to the menopause.

Other factors

There are other factors that may increase your risk of Alzheimer's disease.

There is a link between people who have suffered head injuries and an increased risk of Alzheimer's. Conditions that affect the heart such as high blood pressure, heart disease, high cholesterol, and diabetes can also increase your risk. There is also a higher prevalence of Alzheimer's among Latinos and African-Americans.

What can I do to minimize my risk?

Many of the risk factors involved with Alzheimer's, such as your age and gender, are beyond your control.

There are some steps you can take to reduce the risk caused by other factors.   Stopping Alzheimer's disease before it erases memories, personalities and lives?Yes, it's possible. Using genomic technologies and specialized mouse models to develop preventative therapies, JAX scientists aim to stop Alzheimer’s before it starts.Research has shown  that reducing your risk of conditions that can affect your heart will reduce your risk of Alzheimer's. Quitting smoking, cutting down on alcohol,  Can I Outrun Alzheimer's Disease?What ApoE4, healthy behaviors and other variables might mean for Alzheimer's Diseasegetting regular exercise, and   Does a 'western diet' increase risk of Alzheimer's disease?JAX research provides insight into the role of the western diet in Alzheimer’s disease.eating a balanced diet  can all help both your heart and your Alzheimer's risk. 

There is some evidence that suggests that keeping your mind active may also offer some reduction of risk. Doing something that challenges your brain, such as learning a language or doing word puzzles may help to some extent.

Is there a genetic risk?

There are some other risk factors that are beyond your control that we have not yet touched upon. There is clear evidence that there are several genes that significantly impact your risk of getting Alzheimer's disease. 

There are two types of genes associated with Alzheimer's disease. Risk genes are genes that increase your likelihood of getting Alzheimer's. Deterministic genes, which are rare, guarantee that you will develop the condition at some point.

Late-onset Alzheimer's disease

Late-onset Alzheimer's refers to the much more common occurrence of the symptoms of Alzheimer's appearing at the age of 65 or beyond.

There is a gene called apolipoprotein E (APOE) which is one of the most common risk genes. APOE is usually found in one of three forms. APOE e3 is the most commonly found form of this gene, and it offers no increased risk of Alzheimer's.

APOE e2 is the least common form, and this gene actually seems to reduce the risk of getting the disease. APOE e4 is more common than APOE e2, and it is this gene that increases the risk of Alzheimer's. Since you inherit an APOE gene from both your mother and your father, you may be unlucky enough to inherit two APOE e4 genes, which will increase your risk even further. 

Even having two APOE e4 genes is not a guarantee of getting late-onset Alzheimer's, however; it only means that there is an increased risk of you doing so. About 25 percent of people with one APOE e4 gene develop the disease by the age of 85. That rises to 55 percent for people with two APOE e4 genes. 

Other genes that are linked to late-onset Alzheimer's include ABCA7, CR1, CLU, PICALM, PLD3, TREM2 and SORL1. 

Early-onset Alzheimer's disease

Early-onset Alzheimer's occurs between the ages of around 30 to 65 and is much less common than late-onset Alzheimer's. This type of Alzheimer's shows a strong link to genetic risk factors. 

Research has uncovered mutations in three genes that are deterministic for early-onset Alzheimer's. This means that if you have any of these gene mutations, you will more than likely develop Alzheimer's before the age of 65. These genes are Amyloid precursor protein (APP), Presenilin 1 (PSEN1), and Presenilin 2 (PSEN2).

You can inherit a mutated form of one of these three genes from either parent. The mutations cause a build-up of amyloid-beta peptides which then form into the same amyloid plaques in the brain that Alois Alzheimer first discovered in 1906. 

These genes are not the only cause of early-onset Alzheimer's disease, however. The disease has also been found in people who have no mutations in these genes, so there are also clearly other factors at play.

Down syndrome

Although this is not usually an inherited risk, people with Down syndrome are at an increased risk of getting Alzheimer's disease.

People with Down syndrome are born with an extra chromosome that carries the APP gene. This leads to a build-up of amyloid plaques in the brain, just as in early-onset Alzheimer's. By the age of 40, almost all people with Down syndrome will have these plaques, although not all of them will go on to develop Alzheimer's. 

Estimates are that around 50 percent of people with Down syndrome will suffer from Alzheimer's as they age.

Will I get Alzheimer's?

It's a question we've probably all asked ourselves: Will I get Alzheimer's?

The simple answer is that there's no real way to tell. There are a number of risk factors that can increase your chances of developing the condition, but it is very rare that these factors will guarantee that you will get Alzheimer's at some point.

Much more research is needed into the causes and risk factors associated with Alzheimer's disease, and the good news is that this research is going on right now. The Jackson Laboratory is an independent, nonprofit biomedical research institution that employs more than 2,200 staff. Its mission is to discover precise genomic solutions for diseases such as cancer, diabetes, Alzheimer's disease and more.