Risk Factors for Alzheimer’s Disease

From the lecture series: Understanding the Brain

By Jeanette Norden, PhDVanderbilt University School of Medicine

Alzheimer’s is characterized primarily by the loss of neurons in certain areas of the brain. While there is neuron loss throughout the brain, there are specifically a few areas that show an abnormally high loss of neurons; these include the highest-order areas of the neocortex. The primary areas are left intact, so the individual can see, hear, and walk, but they simply can’t do the higher-order processing necessary to live in the world as a normal human being.

Concept of memory loss and dementia disease and losing brain function memories
(Image: Lightspring/Shutterstock)

For most cases of Alzheimer’s, there is no cause known; only a small percentage can be inherited. For all cases, there is no cure. At this point, the medications try to replace some of the neurotransmitters that have been lost from the loss of the neurons. But neuroscience is discovering which factors increase, or decrease, the risk of developing Alzheimer’s.

Image of a Senior adult
The number one risk factor for Alzheimer’s Disease is age. (Image:  Billion Photos/Shutterstock)

The most important, number one factor that increases your risk of getting Alzheimer’s is age. One in eight people 65 or older have this disease, and for those individuals older than 85, as many as one-half will be diagnosed with this disorder.

Genetics and Lifestyle Factors

Another risk factor is the inheritance of what is called E4/E4 alleles for apolipoprotein E. Alleles are gene variants for a particular molecule that’s produced. In this case, the alleles are for apolipoprotein E, which is a normal molecule found in the brain that’s involved in lipid and cholesterol transport. You inherit one gene from each parent, and for apolipoprotein E, there are three different alleles, or variants, of that gene that you could inherit. Inheriting E4/E4 alleles for apolipoprotein E increases your risk of getting Alzheimer’s or certain forms of Alzheimer’s disease, and so it’s a very critical one. Some companies will look at your allele and determine whether or not you have the E4 alleles for apolipoprotein E—but you can’t alter it. In general, most physicians do not recommend that people do that.

This is a transcript from the video series Understanding the Brain. Watch it now, Wondrium.

Image of Boxing fighters
Head injuries from sports like Boxing can be a risk factor for Alzheimer’s. (Image: Sergey Nivens/Shutterstock)

Head injuries are also associated with an increased risk for Alzheimer’s, either at a concussion or more severe level—anytime that a head injury has significantly interfered with neuronal activity. Scientists discovered this because it turns out that professional boxers, who can sustain more than 50,000 hits to the head in their professional careers, have a significantly increased incidence of Alzheimer’s disease. The consensus is you need to protect your head.

High-fat diets, elevated cholesterol levels, and obesity are also risk factors. This is under our control, so having this as a finding is significant. Several chronic disorders increase the risk too: Atherosclerosis, diabetes, and hypertension. Some individuals have genetic proclivities to have these disorders, and there may be little they can do about that, aside from taking medicines. But for other people, it’s due to lifestyle, so changes can be made. For example, Type II diabetes is related to obesity; that’s something an individual has some control over. If a person can reverse their diabetes, he or she would also decrease his or her risk for Alzheimer’s disease.

Smoking is a risk factor for Alzheimer’s. (Image: Pe3k/Shutterstock)

Smoking has been shown to increase the risk of Alzheimer’s. Not only does it cause lung cancer and many other chronic disorders like emphysema, but it is also a risk factor in developing Alzheimer’s disease.

Another factor that increases the risk of Alzheimer’s disease is a history of clinical depression. Individuals who are chronically depressed or have a history of having true unipolar depression have an increased risk of developing Alzheimer’s.

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A diagnosis of what is called mild cognitive impairment (MCI) is a fairly significant risk factor. This used to be thought of as an entity in itself and is defined as a disorder that involves short-term memory loss but no other cognitive deficits. Originally it was thought that it was a disease that just probably involved the hippocampus, but now it is believed that it’s more than likely the earliest stage of Alzheimer’s. Long-term studies have shown that 80 to 100% percent of individuals diagnosed with MCI will go on to develop Alzheimer’s disease. Most experts now believe those individuals have just been diagnosed at an early stage that doesn’t normally occur.

Hormone replacement therapy—individuals, women who are over 65 years of age who start either taking estrogen alone, or estrogen and progesterone—have an increased risk of dementia and of developing Alzheimer’s disease. Studies are still on-going about what happens if the woman is younger when she starts the regimen; all this is an active area of research for obvious reasons.

The majority of risk factors that increase the risk of developing Alzheimer’s disease are exactly the same risk factors that increase your risk for heart disease and increase your risk for stroke and heart attack.

It is worth noting that the majority of risk factors that increase the risk of developing Alzheimer’s disease are the same risk factors that increase your risk for heart disease and increase your risk for stroke and heart attack.

Learn more about the neurological signs and symptoms of Alzheimer’s disease

Decreasing Risk Through Healthy Lifestyle

Now, that was the bad news. What factors decrease the risk of Alzheimer’s? Well, the inheritance of E2/E2 alleles for apolipoprotein E protects you from ever getting Alzheimer’s disease. This is a very active area of research, for obvious reasons.

image of a salmon steak
Foods rich in Omega 3 Fatty acids, such as this salmon steak, actually decreases the risk of developing Alzheimer’s disease. (Image: hlphoto/Shuttrestock)

Another factor that decreases your risk is eating omega-3 fats, found in cold-water fish like salmon. Eating omega-3 decreases the risk of developing Alzheimer’s disease. The word is still out on whether or not taking supplements has the same effect; it isn’t always true that the body can be fooled by supplements.

Other factors include maintaining a normal weight and avoiding obesity and its associated disorders like diabetes. These are things that are under our control that we can do something about and it’s very important we try. Eat low-fat foods, keep your low-density lipoproteins low, and do all the things that are recommended to help you with heart disease, and this will help you stave off Alzheimer’s disease. Drinking fruit juices and vegetable juices, eating fruits and vegetables, and drinking certain kinds of teas that are high in antioxidants are implicated in decreasing the risk of developing Alzheimer’s. Again, these are simple changes we can make in our lives that may not prevent us from getting the disease, but they certainly play a role.

Exercise Plays a Key Role

The next factor is exercise. In some of the cutting-edge research that’s going on in neuroscience right now, recent studies have shown that the hippocampus is one of the few areas of the brain that continues to undergo mitosis throughout life. Furthermore, the most recent studies have shown that exercise increases mitosis in the hippocampus. By staying physically active, you generate more new neurons in the structure that’s involved in memory in your brain. It’s not going to replace your old memories to generate new neurons, but it will allow you to form new memories, and so this is a very positive indicator. We’ve become sedentary as a society. Even if we don’t develop a disorder like Alzheimer’s, we need to keep ourselves active. Exercise is going to help us maintain our memory and mental activity into old age.

One of the other important factors is continuing mental “challenge.” Continually challenging your mind—and it has to be something that challenges you, like taking a course, learning a new language, learning how to play the piano, or doing something similar—is a major way of decreasing the risk of developing Alzheimer’s disease.

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Even if you follow everything and you do everything the way you are supposed to, it doesn’t mean that you might not get this disease; Alzheimer’s is the number one neurological disease in the United States. But it matters that we identify factors, particularly those under our control, that might help us be able to decrease the risk of getting this terrible condition.

Common Questions About Alzheimer’s

Q: What are the stages of Alzheimer’s?

There are seven stages of Alzheimer’s, beginning with the first one where Alzheimer’s is undetectable, and progressing to further and further levels of decline.

Q: In what way does Alzheimer’s kill you?

Alzheimer’s itself doesn’t kill the patient. Alzheimer’s shuts down areas of the brain systematically until a vital area such as one responsible for breathing or swallowing fails, and this leads to the patient’s death.

Q: Are there any first signs for Alzheimer’s?

The first signs of potential Alzheimer’s if the person is of age are memory loss and difficulty planning, making decisions, or doing logical tasks.

Q: Is there a difference between Alzheimer’s and dementia?

The difference between Alzheimer’s and dementia is that Alzheimer’s is a disease whereas dementia is a syndrome or set of conditions that Alzheimer’s can actually fall under.

This article was updated on December 2, 2020

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