Risk and Dementia – Genetics

For some types of diseases that cause Dementia to occur, there is a genetic association for having the disease by the time an individual is 60-years of age or older. It’s a subtle distinction, but people who have the altered gene inherit the risk and not the disease itself. In fact, Dementia is not a disease, rather, it is the expression of the cognitive challenges that come about because of the changes in brain tissue, caused by a particular disease.

This post mainly focuses on Alzheimer-caused Dementia but there are many other causes, e.g., Lewy body, Vascular, Frontotemporal, et al.

On the bright side, knowing that you have an inherited risk factor gives you the opportunity to do those things known to reduce risk - maintain a healthy weight, refrain from smoking, engage in socially and intellectually satisfying activities, exercise, and eat a heart-healthy diet.

For the most part, the at-risk genes change how the body processes cholesterol and other blood lipids. Therefore, it’s not surprising to find that having high cholesterol blood-levels is another risk factor associated with having Dementia later-in-life.

Early-onset familial Alzheimer disease (eFAD) is inherited Dementia that affects people as young as 30 years of age. (1) Unlike traits that are observable shortly after birth, such as eye color, symptoms of eFAD do not appear until the individual is 30-years of age or somewhat older. By that time, it is likely he or she has one or more children and may have unknowingly passed the early-onset gene to them.

Fortunately, there are DNA tests that can identify the presence of the increased-risk genes as well as those that cause eFAD. 

Making the decision to undergo testing is difficult. Will knowing make you feel anxious, relieved, or empowered? Will other family members also want testing? How might this information affect family planning for you or your adult children? Will having a positive test for a specific cause of Dementia risk factors or early-onset disease influence your employer, your career, or make it more difficult to receive health insurance? (2)

Often, people find talking with a genetic counselor can make the decision to test--or not--easier. The genetic counselor, by explaining the technical and emotional issues associated with genetic testing, can help you make a personally comfortable decision. Afterward, the genetic counselor can explain the test results to you and guide discussion about any further steps you may want to take. (2)

You can find more information about genetics and genetic counseling on the following webpages: National Association of Genetic Counselors (https://www.nsgc.org/page/find-a-genetic-counselor)and the American Board of Genetic Counselors (https://www.abgc.net/about-genetic-counseling/find-a-certified-counselor.aspx/). Both of these sites may help you find a genetic counselor located near your home.

Notes:
1. What is Early Onset Familial Alzheimer Disease? http://www.alzforum.org/early-onset-familial-ad/overview/what-early-onset-familial-alzheimer-disease-efad (accessed April 26, 2016)
2. Genetic Testing and Counseling for Early Onset Familial Alzheimer Disease, http://www.alzforum.org/early-onset-familial-ad/diagnosisgenetics/genetic-testing-and-counseling-early-onset-familial (accessed, April 26, 2016)

Want to Know Even More?
Alzheimer Disease Genetics Fact Sheet, https://www.nia.nih.gov/alzheimers/publication/alzheimers-disease-genetics-fact-sheet#genetics
(accessed, April 26, 2016)

Contributor: Janet Yagoda Shagam, PhD, is a freelance medical and science writer and the author of “An Unintended Journey: A Caregiver's Guide to Dementia.” Available through Amazon.

The opinions expressed by contributing authors are not necessarily the opinions of the Dementia Society, Inc. We do not endorse nor guarantee products, comments, suggestions, links, or other forms of the content contained within blog posts that have been provided to us with permission, or otherwise. Dementia Society does not provide medical advice. Please consult your doctor. www.DementiaSociety.org

What Causes Dementia?

We don't know exactly. What actually causes dementia is a difficult question. There are an infinite number of factors that singly or in combination may increase risk for, or are associated with having dementia. To add to the mind-boggling complexity, each of us are the outcome of a unique collection of genes, lifestyle behaviors and environmental exposures.

Similar to the word “cancer” the word “dementia” is an umbrella term that includes many kinds of dementia. And again, similar to cancer, the dementias share certain characteristics such as memory loss, but also have ones specific to a particular type of dementia.  For example, Alzheimer disease tends to have a slow progression and vascular dementia tends to progress with bursts of increased disability.

In the case of early-onset Alzheimer disease, the answer might be less complicated than it is for other kinds of dementia. Scientists have identified genes that appear to cause the kind of dementia that strikes people younger than 65-years of age. People who have early-onset dementia genes can pass the trait on to their children. However, even these findings open the door to more questions. Do the early-onset genes actually cause the disease or do they increase risk to the extent that makes having early-onset dementia a given. Perhaps the relationship between genetics and this form of dementia involves other genes and factors, that in combination, cause early-onset dementia. 

Genetics may or may not play a role in the onset of other kinds of dementia. For example, approximately 15 to 40 percent of people who have frontotemporal lobe degeneration have a family history that includes at least one other relative who also has or had this kind of dementia. However, only 10 percent of these individuals have a form of the disease attributable to specific genes. This means that for 90 percent of cases, scientists have yet to discover genes that increase risk for having Frontotemporal lobe dementia. 

Although one cannot change their genetics, it is possible to reduce risk for dementia by modifying certain lifestyle behaviors. 

There are many lifestyle behaviors that appear to increase risk for dementia. Some of these include obesity, high blood pressure, smoking, diabetes, and lack of regular exercise. Social isolation, not having meaningful friendships, also appears to increase risk for dementia. Another risk factor is not having the mental stimulation that comes with acquiring new skills and knowledge. 

The good news is one can choose to reduce the likelihood of dementia by losing weight, eating a healthy diet, refrain from or stop smoking, exercising, as well as by attending community center activities or taking classes at a local college or university. 

Unlike behavioral changes, it’s difficult to impossible to avoid environmental risk factors. While one can make efforts to avoid environmental toxins such as second-hand smoke, it’s not possible to avoid to the fumes that come from car exhaust or from certain kinds of building materials. 

Over the past 50 years, there has been a dramatic change in the 10 leading causes for death. Deaths caused by acute infectious diseases and accidents have given way to lingering diseases such as cancer and dementia – both of which tend to occur later-in-life. Therefore, for many people, advanced age is their biggest risk factor for having dementia.

Janet Yagoda Shagam, PhD, is a freelance medical and science writer and the author of “An Unintended Journey: A Caregiver's Guide to Dementia.” Available through Amazon.

The opinions expressed by contributing authors are not necessarily the opinions of the Dementia Society, Inc. We do not endorse nor guarantee products, comments, suggestions, links, or other forms of content contained within blog posts- that have been provided to us with permission, or otherwise. Dementia Society does not provide medical advice, please consult your doctor. www.DementiaSociety.org