Many People Who Have Watched A Family Member Suffer The Effects Of Alzheimers Disease Wonder If Its A Genetic Condition And If Theyll One Day Undergo The Same Symptoms
While theres no cure for this irreversible, progressive disease, scientists and researchers are learning more about it every day. One thing we do know about Alzheimer’s is that of the two types early onset and late onset both have a strong link to genetics.
According to Alzheimers research, some cases of early-onset Alzheimers disease are caused by genetic mutations that are inherited from your parents. In fact, a person whose mother or father carries a genetic mutation for early-onset Alzheimers disease has a 50 percent chance of also having that mutation.
And, if they do inherit that that genetic mutation, the chances of developing early-onset Alzheimers disease are high. When it comes to late-onset Alzheimers, scientists arent entirely sure exactly why it develops or what causes it.
Theres a general belief among Alzheimers researchers that a combination of several factors genetics, lifestyle, and environment lead to the condition. Theres no specific gene that has been linked directly to late-onset Alzheimers disease, though researchers have determined that having a certain kind of the apolipoprotein E gene or any of its variants on chromosome 19 can increase your risk of developing the disease.
What Conditions Can Be Mistaken For Dementia
The term dementia refers to a specific group of symptoms related to a decline in mental ability. Often, people who experience subtle short-term memory changes, are easily confused, or exhibit different behaviors or personality traits are mistakenly thought to have dementia. These symptoms could be the result of a variety of other conditions or disorders, including other neurocognitive disorders such as Parkinsons disease, brain growths or tumors, mild cognitive impairment , and mood disorders, like depression.
If Youre Considering Utilizing A Dna Test You May Feel A Bit Overwhelmed By All The Options Available To Purchase Online Or To Have Administered Through Your Doctors Office
Heres the difference between a handful of common DNA tests that you may have seen commercials for or encountered online.
Ancestry DNA tests: This kind of DNA test is the kind you may have seen ads for, where it says submitting a DNA sample can help you find out more about your family history. Ancestry DNA tests are becoming more and more popular around the globe, and they often come with additional features such as family tree databases to help you compile your genealogy.
And, if you choose to participate, these DNA tests can also compare your DNA to that of people who have also submitted a test to identify potential relatives, which can work in the benefit of people who are adopted or dont know much of their family. Popular ancestry DNA tests include AncestryDNA, Family Tree DNA, and MyHeritage DNA, though more and more companies are offering this kind of DNA testing as time goes on.
At-Home Medical DNA tests: As more people want to know about their genetics, DNA testing companies have developed a variety of DNA test kits that can clue you on potential personal health risks. One of the biggest draws of these tests is that they can be taken within the privacy of your own home and theyre affordable which means that the information you gain from these tests can help you understand your personal health situation without the expense of a doctor-ordered DNA test.
If youre a woman, you wont have any Y-DNA for a DNA test kit to reveal .
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Understanding Apoe And Risk Of Late
ApoE is most commonly linked with late-onset Alzheimers, a form of the disease which usually occurs in people over the age of 65 and accounts for the majority of Alzheimers cases. The gene comes in three common forms, or alleles: E2, E3 and E4. Everyone inherits an ApoE gene from each biological parent, and there are six possible ApoE combinations: E2/E2, E2/E3, E2/E4, E3/E3, E3/E4, E4/E4.
Analyzing data from past research of individuals who are cognitively healthy, Langbaum and colleagues found in a study that people who carry two copies of ApoE4 have a 30 to 55 percent risk of developing mild cognitive impairment or Alzheimers by the age of 85. The study also shows a 20 to 25 percent risk for people with one copy of the genetic variant. People with two copies of ApoE3 have an estimated risk of 10 to 15 percent. The researchers had less information available about people with ApoE2 as its rare, estimating that its associated risk with Alzheimers may be slightly lower or higher than 10 to 15 percent by the age of 85.
Genetic Testing For Alzheimers Disease
James M. Ellison, MD, MPH
Swank Center for Memory Care and Geriatric Consultation, ChristianaCare
- Expert Advice
Learn about the most common genes associated with the early- and late-onset forms of Alzheimers disease, and the current recommendations for genetic testing.
Can Alzheimers or other forms of dementia be passed along in the genes we inherit?
This is a very common question people ask, and the answer is not the same for all kinds of dementia. In this article we will focus on Alzheimers disease .
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Role Of Genetic Testing
As noted earlier, with the exception of EOAD in descendants of affected individuals in high-risk, early-onset families, genetic testing for AD is not recommended at this time. Even for the small percentage of cases of EOAD, detection does not lead to reversal of the disease because there is no known cure for any form of AD. However, diagnosis can aid in increasing a patient’s quality of life and facilitating planning for life care and financial needs. In addition, a positive genetic test can end the quest for a specific diagnosis. There is some indication that APOE 4 is an indicator of poor response, especially in women, to acetylcholinesterase treatments, which has obvious implications for drug prescriptions.
When Is Genetic Testing For Dementia Appropriate
In some cases, it may seem likely that a persons dementia is caused by a single-gene change for example, if the person has a very strong family history of dementia. In these cases, it may be appropriate to offer genetic testing to the person and to their family.
However in most families dementia will not be caused by a single-gene change. In these cases, genetic testing will not be appropriate. This is because testing for risk variants does not provide any certainty about the persons chances of developing dementia.
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Symptoms Of Alzheimers Disease
Memory loss Repeating things, often forgetting conversations or appointments, routinely misplacing things, eventually forgetting the names of family members and everyday objects.
- Problems with abstract thinking People with Alzheimers may have trouble recognising and dealing with numbers.
- Difficulty finding the right word It may be a challenge for those with Alzheimers to find the right words to express thoughts or even follow conversations. Eventually, reading and writing also are affected.
- Disorientation- People with Alzheimers disease often lose their sense of time and dates, and may find themselves lost in familiar surroundings.
- Loss of judgment Solving everyday problems, such as knowing what to do if food in the oven is burning, becomes increasingly difficult, eventually impossible. Alzheimers is characterized by greater difficulty in doing things that require planning, decision making and judgment.
- Difficulty performing familiar tasks- Once-routine tasks that require sequential steps, such as cooking, become a struggle as the disease progresses. Eventually, people with advanced Alzheimers may forget how to do even the most basic things.
- Changes in personality.
Why I Dont Want To Know My Genetic Risk For Alzheimers Disease
I have studied brain health and risk reduction for Alzheimers disease and related dementias for more than ten years. While there is no disease-modifying therapy available on the market today, there is emerging evidence that many common-sense lifestyle choices can improve the resilience of our brains and decrease our risk of developing dementia.
In 2017, the Lancet Commission released a growing body of evidence suggesting that nine risk factors could be modified to help delay or prevent dementia: less education, hypertension, hearing impairment, smoking, obesity, depression, physical inactivity, diabetes and low social engagement. In 2020, the Commission added three more modifiable risk factors to its list to make a total of twelve, accounting for around 40 percent of worldwide dementias.
My father and his three siblings all had late-onset Alzheimers disease. It is a cruel, mind-robbing disease, and I wish it upon no one. This is why in 2020 I launched the Milken Institute Alliance to Improve Dementia Care, a cross-sector collaborative that includes more than 60 leaders across eight stakeholder groups: advocacy, research, health systems, industry, philanthropy, government, community-based organizations and people living with dementia and their caregivers.
Im not sure what I would do differently if I knew I had the APOE e4 gene, so I choose not to be tested.
Reducing Risk Already
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Genetic Testing And Counseling For Early Onset Familial Alzheimer Disease
“I am finding out this month. If I have it, I will never have kids. It’s got to stop somewhere in our family.” Tom Drury , 36.
“If I knew I carried the mutation, I would not be able to get up in the morning.” Jane Smith , 26, at risk for eFAD.
Interview with a Genetic Counselor: Jennifer Williamson is a genetic counselor at the Taub Institute for Research on Alzheimer’s Disease and the Aging Brain and the Gertrude H. Sergievsky Center at Columbia University, New York
Genetic Status Protocol: Get a sense of the careful process you may want to ask for should you decide to find out about your genetic status.
Introduction Early onset familial Alzheimer disease is an autosomal-dominant genetic disease. This means that in each family it is caused by a mutation in a single gene, and that a single copy of the mutant gene, inherited from one parent, will cause the disease. The discovery in the mid 1990s of eFAD genes aroused the specter of knowing one’s genetic future, not only for patients but also for their children and entire families. Indeed, the age of genetic testing is here. DNA testing has been used since the mid-1990s for Huntington disease and certain types of cancer. The experience with these families provides helpful guidance for families with eFAD, who have turned to genetic testing more recently. Indeed, there is a large literature on genetic testing for HD and a small but growing literature for AD.
What Does Pgd Involve
PGD involves the following steps:
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How Is It Used
APOE genotyping is sometimes used as an added test to help in the diagnosis of probable late onset Alzheimer disease in symptomatic adults. However, the association of the e4 allele with late onset AD does not mean that it causes AD, only that more people with late onset AD have e4 alleles compared to similar aged peers without late onset AD. For this reason, APOE genotyping is referred to as susceptibility or risk factor testing since it indicates whether there is an increased risk of AD but is not specifically diagnostic of AD. For example, if a person has dementia, the presence of APOE e4 may increase the likelihood that the dementia is due to AD but does not prove that it is.
There are no clear-cut tests to diagnose Alzheimer disease during life. Healthcare practitioners can, however, make a reasonably accurate clinical diagnosis of AD by ruling out other potential causes of dementia and checking for a genetic predisposition to AD with APOE genotyping as supplemental information in conjunction with tau protein and beta amyloid testing.
What Does The Test Result Mean
People who have symptoms of Alzheimer disease and have one or more APOE e4 copies are more likely to have AD. However, it is not diagnostic of AD and should not be used to screen asymptomatic people or their family members. Many individuals who have APOE e4 alleles will never develop AD. Even in symptomatic people, only about 60% of those with late onset AD will have APOE e4 alleles.
Although APOE genotyping may be used clinically by Alzheimer experts, it can only provide additional information about a person with dementia. A definite diagnosis of Alzheimer disease can only be made by examining a persons brain tissue after their death.
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Scientists Have Identified Genetic Mutations That Cause Early
While researchers have found genetic risk factors for late-onset Alzheimers, they have, on the other hand, identified rare genetic mutations that cause early-onset Alzheimers, which affects people younger than the age of 65.
Langbaum said people who carry hereditary genetic mutations in one of three genes PSEN1, PSEN2 and APP nearly always develop the disease. They account for less than 1 percent of all people with Alzheimers.
She noted that the decision to order genetic testing for a genetic mutation that causes early-onset Alzheimers is typically made between the patient, clinician and in many cases, family members.
Meanwhile, there seems to be certain genetic factors that may be protective against Alzheimers. Scientists from the Banner Alzheimers Institute and colleagues found that an extremely rare variant of ApoE, known as the Christchurch mutation, appeared to protect a Colombian woman from the ravages of the disease.
The woman, who carried the PSEN1 mutation and two copies of the Christchurch mutation, had normal cognitive abilities until her 70s when she began to develop memory decline. Even though she had high levels of beta-amyloid plaques in her brain, there were very limited atrophy and tau pathology.
For more guidance on this topic to be the first to know about upcoming live talks with experts on practical topics related to Alzheimers, dementia and caregiving.
Most Cases Of Alzheimers Are Not Caused By A Single Gene
The good news is that most cases of Alzheimers disease are not passed along by a single gene. Among the millions of people in the world affected by AD, those known to have developed the disease due to the inheritance of a single gene account for a very small percentage.
The bad news is that even without inheriting one of the genes that are known to transmit AD, the disease is still a significant health risk for any older adult.
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Apoe: A Marker For Alzheimers Risk
Experts believe there is a strong genetic component to Alzheimers disease. But for late-onset Alzheimers disease, the most common form of dementia that appears after age 65, it doesnt boil down to just genetics. Rather, there could be multiple genes as well as other lifestyle and environmental factors that play into whether a person develops the disease.
As of now, the gene that seems to be the strongest predictorof Alzheimers risk is called ApoE. There are three varieties of this gene:
- ApoE2
- ApoE3
- ApoE4
Each person has two copies of ApoE genes. Studies have shown that a person who carries the ApoE4 variety is at an increased risk for developing Alzheimers. Having one copy of ApoE4 can triple a persons risk, Dr. Sabbagh says, and having two copies raises the risk even further.
But ApoE4 is not a deciding factor for Alzheimers. Its a statistical risk, but its not an absolute risk, Dr. Sabbagh reiterates.
That means that having ApoE4 doesnt mean youre guaranteed to develop Alzheimers, and not having it doesnt necessarily put you in the clear.
That uncertainty is part of why its important to carefullyconsider whether knowing your ApoE4 status would benefit you.
Future Of Alzheimers Blood Tests
When blood tests become mainstream, they will significantly impact the way doctors diagnose and even treat the condition.
Beyond the Preclivity AD and Simoa described above, there are multiple other types of blood tests in development some are looking at protective fats in the blood. Research shows that an increase in fatty amide levels indicates more beta amyloid in the brain. Beta amyloid plaques have been found in the brains of people with Alzheimers.
Other blood tests will measure proteins such as tau proteins and the neurofilament light chain protein. Researchers have found that neuron death, characteristic in people with Alzheimers, may be detected by the corresponding increase of these proteins in the blood.
It is also possible that the probable link between insulin resistance, diabetes and Alzheimers means blood tests could show the disease in someone well before symptoms occur. Another protein called IRS-1 is commonly associated with diabetes but has also been linked to Alzheimers. Studies have shown that someone with Alzheimers has more IRS-1 than even someone with diabetes.
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The Effect Of Knowing Your Status
One of the major drawbacks to being tested for the ApoE4 gene is that the test is considered what is called a susceptibility test because it has limited predictive value. Having the E4 allele does not mean that a person will be diagnosed with Alzheimers. Many E4 carriers may live long lives without ever developing the disease, and many noncarriers still have risk for Alzheimers. This is critically important to understand before having genetic testing for ApoE4.
Several studies have now examined the impact of ApoE4 testing on individuals. The NIH REVEAL-SCAN project examined the effect of learning ApoE4 status in those who were not showing any symptoms of dementia but had first-degree relatives affected by Alzheimers. The data indicated that knowing ones ApoE status caused only mild and brief psychological problems in those found to have inherited E4 alleles.
In a more recent study, adverse psychological reactions were reported by a fraction of the participants, including those who had specifically sought testing. However, nearly all of those interviewed said that they had benefited in the long term from lifestyle changes they subsequently made.