Your age, genes and family history all help determine your risk factors for Alzheimer’s. Previously unsuspected medical, lifestyle and environmental factors may also increase your risk. New research shows that conditions, like diabetes, also may increase your risk of developing AD, even accelerate it. While you can’t change your age, genes or gender, you may be able to lower other risk factors.
Assessing the Risk
The chances of developing Alzheimer’s are likely affected by your genes, cognitive health, the environment, your lifestyle and other factors. Researchers are looking for ways to define and measure these variables to assess your overall risk.
FACT: Your probability of having AD is a sum total of a variety of factors, explains neuroscientist Gary Lynch of University of California, Irvine. If, for example, you were born with a particular gene mutation and banged your head on the pavement when you were 12, the likelihood of you getting Alzheimer’s would be greater than if you had the right genes and wore a helmet when biking.
Factors, including smoking, head trauma, depression, marital status and how often you exercise, have been associated with Alzheimer’s. None of them predicts your chances of getting the disease with any accuracy but a combination of them could.
Early-onset Alzheimer’s (sometimes referred to as younger-onset AD) is a rare form of the disease that strikes individuals between 30 and 60 and accounts for less than 10 percent of all cases. While it occasionally strikes those in their 30s, most of those diagnosed are middle-age, usually in their 50s.
FACT: According to the Alzheimer’s Association, some 500,000 people in their 30s, 40s and 50s have Alzheimer’s or a related dementia.
One form of early-onset AD, known as early-onset familial Alzheimer’s (or FAD), accounts for less than five percent of AD diagnoses overall. FAD is caused by gene mutations on chromosomes 1, 14 and 21, each of which causes excess production of beta-amyloid, a key component of toxic plaques that are characteristic of AD.
FAD is autosomal dominant. That means if you inherit even one abnormal gene from one of your parents, you are practically guaranteed to develop Alzheimer’s before you’re 65. Only several hundred families worldwide carry the gene mutations that trigger this rare form of AD.
Your genes play a less decisive role in late-onset Alzheimer’s. This more common form of the disease affects those over 65.
So far, scientists have identified one risk gene for late-onset, called Apolipoprotein E4 (ApoE4). It’s one of three common variations of the ApoE4 gene (or alleles), which codes for a protein that helps carry cholesterol in your bloodstream. Two other common variations, ApoE2 and ApoE3, are also linked with Alzheimer’s in different ways.
· ApoE2, the least common form, is relatively rare. It appears to reduce the risk of AD and may even delay the onset of symptoms.
· ApoE3, the most common form, plays a neutral role in the disease. It doesn’t increase or decrease the risk.
· ApoE4, found in roughly 40% of those with Alzheimer’s, appears to increase the risk.
Those with ApoE4 inherit an increased risk of developing Alzheimer’s, not the disease itself. Some individuals with one or more ApoE4 alleles, never get the disease, while others develop AD without any.
Scientists are still trying to understand how ApoE4 increases a person’s susceptibility to Alzheimer’s. Some suspect the allele plays a lesser role in whether you get Alzheimer’s than in when you get it. That’s because it lowers the age at which symptoms appear and may accelerate the disease’s progression. The average age of onset for Alzheimer’s symptoms is 84 among those with no copies of ApoE4; 75 in those with one copy (inherited from one parent); and 68 in those with two copies (inherited from both parents).
FACT: Eating a high-fat diet appears to increase your risk for Alzheimer’s. A small group of health practitioners, including Pamela McDonald, an integrative medicine nurse practitioner and author of the ApoE Gene Diet, maintain that knowing the combination of ApoE genes you carry can help you modify your diet and make lifestyle changes that can help reduce your risk for Alzheimer’s and other diseases.
Experts believe there may be as many as a dozen other Alzheimer’s risk genes. Evidence is building that ApoE4 raises other Alzheimer’s risks, such as early memory loss, sensitivity to the effects of head injuries and cardiovascular diseases. According to a recent study, those who have one or two copies of ApoE4—who also had a parent with dementia—were two to three times more likely to experience memory problems in mid-life. Genetics Home Reference, a service of the U.S. National Library of Medicine, claims that those carrying at least one copy of ApoE4 have an increased chance of developing atherosclerosis or the accumulation of fatty deposits and scarlike tissue in your arteries.
A blood test is available that can identify which ApoE alleles you carry. Since the ApoE4 gene is only a risk factor for AD, the test won’t tell with any certainty whether or not you’ll develop the disease.
Most Alzheimer’s experts discourage genetic testing for ApoE4. That thinking may change, however, as we learn more about the genetic and lifestyle risks for Alzheimer’s. Anyone who’s considering the ApoE4 screen should consider these issues.
· Most insurance plans don’t cover the testing.
· Roughly 25% of the U.S. population carry one copy of the ApoE4 gene and will test positive.
· One-half of those with Alzheimer’s don’t test positive. Just because you don’t carry the gene doesn’t mean you won’t develop AD.
· At least 20% of those with ApoE4 don’t develop Alzheimer’s.
· Whether or when an individual with ApoE4 develops Alzheimer’s depends on many factors, including other diseases and lifestyle risks.
· Inheriting one copy of the ApoE4 gene puts you at approximately the same risk as having a parent with the disease.
As some experts see it, the ApoE4 is a less-than-perfect predictor and the results may cause some people to become worried or despondent. In the proper context, however, ApoE4 testing may provide useful information to ApoE4 carriers, encouraging them to protect themselves against high cholesterol.
That’s all for today. Thanks for listening. I hope this information was helpful.
Join me at 1 pm Monday when I’ll talk more about the Alzheimer’s risks.
Own and operate an Internet Talk Radio Network for 10 years, 2005 to Present
Published Author of Non-Fiction Book, 1996, "Teenagers! A Bewildered Parent's Guide.
Published Author of several fiction books, 2006 "Sacred Honor" and 20010 "The Anna Mae Mysteries: The Golden Treasure."
Playwright of Theater of the Absurd and Black Comedies.
Screenwriter, Black Comedies