Question: My mother has Alzheimer’s disease. Does that mean I will get it?
Answer: Let’s start with some basic numbers. Excellent data from Canada indicates that eight per cent of people over the age of 65 will be diagnosed with dementia, and about two-thirds of those will have Alzheimer’s disease. The risk of developing Alzheimer’s disease doubles for every five years of life beyond age 65, making older age one of the most significant and predictable risk factors.
Familial Alzheimer’s disease
In terms of risk for family members, it is important to know that there are two types of Alzheimer’s disease. A very rare form of the illness, referred to as “Familial Alzheimer’s disease” occurs in only about 2 per cent of individuals with the illness, and has been linked with three genetic mutations involving chromosomes 21, 1 and 14.
In this form of the illness, there is a 50 per cent chance of developing the disease if you have a parent with the illness who has a confirmed genetic mutation. The other disturbing aspect of this illness is that — unlike the more common form of Alzheimer’s disease that typically begin in a person’s 70s and 80s — this form of the illness can begin as early as in a person’s 40s and 50s. Genetic testing is available for this, and I will discuss the topic of genetic testing in a future blog.
Sporadic Alzheimer’s disease
Most people who develop Alzheimer’s disease have what is called “Sporadic Alzheimer’s disease,” to distinguish it from Familial Alzheimer’s Disease. But even with this form of the disease, genetics appear to play a role.
If you have a first-degree relative with Alzheimer’s disease (e.g. mother, father, sibling), your risk of developing the illness is about two to three times higher than someone else your age who doesn’t have a family member with the illness. If you have two first-degree relatives with Alzheimer’s disease, your risk is probably closer to five to six times higher. While families often worry and focus on these risks, I try to get them to consider the other risk factors for the disease. After all, there is very little we can do about our genetic make-up!
Non-genetic risk-factors
Besides aging and genetics, numerous other Alzheimer’s risk factors have been proposed, though admittedly, many of these are not supported by similar kinds of excellent, consistent data. Better educational attainment and lifelong participation in mentally stimulating work and leisure activities appears to be protective. Head injuries likely increase the risk. Physical exercise may decrease the risk of developing dementia, and possibly slow the decline of the illness once diagnosed. A Mediterranean-type diet (low in saturated fats and red meats, more fish, vegetables and nuts, legumes and olive oil) appears to be protective. Mid-life vascular risk factors such as smoking, obesity, high blood pressure, high cholesterol and blood sugar, all increase the risk of developing Alzheimer’s disease and other forms of dementia.
As you will appreciate — unlike aging and genetics — many of these risk factors are potentially under our control. In future blogs, I will explain how these can be the basis for living a brain-healthy lifestyle to reduce the risk of developing Alzheimer’s disease and other dementias.
Have a question for the Memory Doctor? Please post it in the comment box below and Dr. Herrmann will respond within 1-2 business days.
Dear Dr. Herrmann,
My father was diagnosed with alzheimer’s at the age of 58 however we noticed changes in his behaviour a few years before that age. At the age of 58 he also encountered a retinal detachment. Recent studies are showing some correlation between retinal thinning and dementia/alzheimer’s disease. I am turning 31 in September and last year was advised by an optometrist I have retinal thinning. Are my chances of developing early on set AD now higher since my father is diagnosed with this and I appear to have retinal thinning?
If so, what are my next steps? Are there studies I can participate in to further investigate retinal thinning and decline in cognitive functions?
Thank you
Hi,
It is only recently that researchers have recognized that the eyes may be the windows into the brain of patients with dementia including Alzheimer’s disease. There are some small preliminary studies that have shown a number of measures of eye structure, including the thickness of retina, easily measured by a method called Optical Coherence Tomography (OCT) scanning, is not only associated with dementia severity, but may predict who will develop dementia. As I always emphasize, these studies are very small, preliminary and require replication in larger, longer studies in order to truly understand how accurate they are and to determine whether these tests belong in daily clinical practice.
Having a first degree relative with Alzheimer’s Disease, such as a parent, in and of itself, probably doubles the risk of developing the illness, especially when the disease starts before the age of 65.
There are a number of studies running in Canada and the US that are aimed at patients at high risk for developing Alzheimer’s Disease, including OCT studies. I generally recommend starting with the Alzheimer’s Society of Canada (http://alzheimer.ca/en/Home/Research) which lists many of the studies currently running in Canada, hopefully in a community close to you.
Dear doctor,
Both of my grandmothers had/ has Alzheimer’s and ive recently had 2 aunts and an uncle diagnosed(father’s side). My maternal grandmother’s father also had Alzheimer’s. Im very concerned about my chances of developping the disease and was wondering if you could help clarify for me the chances of my getting it. Thanks for your time, kathleen.
My mom had early onset Alzheimer’s and died at 60. My grandfather’s got dementia at 91. My great grandmother had Alzheimer’s in her 70s. Is this familial? My uncle is unaffected. I’m a mom of 5 kids and I’m very worried about getting Alzheimer’s or my kids getting it when they are older. Does Ohip cover genetic tests in this case?
Without taking a detailed personal medical history and a careful family history which includes all family members with and without the disease, and the ages at which those affected developed symptoms, providing an accurate risk assessment is not possible. Even with this information risk profiling is still more art than science at this point, with the exception of the very rare forms of Familial Alzheimer’s Disease mentioned in my blog, which can be detected by genetic testing.
My recommendation to those readers with concerns about their risk of developing dementia either with strong family histories, is to start a discussion with their family physician about all risk factors (including lifestyle and diet) and request a referral to a dementia specialist. A dementia specialist can determine whether genetic testing is indicated and/or might refer the person to a clinical geneticist, who would be able to provide the testing and appropriate counselling regarding genetic risks.
Finally, I would remind the readers that at the moment, there is no cure or effective disease modifying therapy for Alzheimer’s Disease or the other forms of dementia, and therefore knowing one’s genetic risk may be unhelpful and even potentially emotionally harmful. At the present time, instead of focusing on your genetic risk which is unmodifiable, we should all be trying to improve our general medical health and lifestyle habits including exercise, diet and mentally stimulating activities which have shown the best evidence of reducing the risk of dementia. @yidchick:disqus
Hi Kathleen. Without taking a detailed personal medical history and a careful family history which includes all family members with and without the disease, and the ages at which those affected developed symptoms, providing an accurate risk assessment is not possible. Even with this information risk profiling is still more art than science at this point, with the exception of the very rare forms of Familial Alzheimer’s Disease mentioned in my blog, which can be detected by genetic testing.
My recommendation to those readers with concerns about their risk of developing dementia either with strong family histories, is to start a discussion with their family physician about all risk factors (including lifestyle and diet) and request a referral to a dementia specialist. A dementia specialist can determine whether genetic testing is indicated and/or might refer the person to a clinical geneticist, who would be able to provide the testing and appropriate counselling regarding genetic risks.
Finally, I would remind the readers that at the moment, there is no cure or effective disease modifying therapy for Alzheimer’s Disease or the other forms of dementia, and therefore knowing one’s genetic risk may be unhelpful and even potentially emotionally harmful. At the present time, instead of focusing on your genetic risk which is unmodifiable, we should all be trying to improve our general medical health and lifestyle habits including exercise, diet and mentally stimulating activities which have shown the best evidence of reducing the risk of dementia.