What are Alzheimer’s Risk Factors?

As we learn more and more about Alzheimer’s disease, the picture that emerges becomes increasingly complex. We understand today that the dis­ease has no single cause, and that even some factors that once seemed directly causal are in fact blended with others in a sort of web of causation. Some of those Alzheimer’s predisposing factors, such as genetics, are beyond our con­trol. With respect to others, especially diet and exercise, we can improve our chances of avoiding Alzheimer’s. We call those “modifiable risk factors,” since we enjoy some degree of control over them.

A Non-Modifiable Risk Factor: Genetics

Family history may play a role in whether a person is diagnosed with Alz­heimer’s. In fact, your risk doubles if you have parents or siblings with the disease. While in most cases, no single gene can be thought of as “causing” Alzheimer’s, the presence of certain gene types can increase someone’s risk. The strongest such example is a gene that codes for a protein called apolipoprotein E (ApoE), which breaks down fats. Hav­ing multiple copies of an ApoE subtype called ApoE4 drives up Alzheimer’s risk. About 65% of people with Alzheimer’s have this gene subtype, although having it does not necessarily mean you’ll get the disease.

Out of all Alzheimer’s cases, about 1% are considered “genetically deter­mined,” meaning that the genetic profile makes the disease inevitable. This is also known as “familial” Alzheimer’s disease, and it usually sets in between ages 30 and 60, much earlier than typical. Having Down Syndrome also dras­tically increases the likelihood of developing the kinds of brain changes seen in Alzheimer’s. That’s likely because people with Down Syndrome have three copies of the chromosome that carries the gene most closely associated with the development of amyloid plaques.

A Non-Modifiable Alzheimer’s Risk Factor: Age

Unsurprisingly, the older you get, the greater are your chances of developing Alzheimer’s. Only about 5% of people between 65 and 74 have the disease, but that figure bumps up to 13% in the 75-84 age group. And fully a third of people 85 and older have Alzheimer’s. Looked at another way, though, you can say that two-thirds of adults 85 and older are Alzheimer’s-free, which under­scores the fact that the disease is not an inevitable part of aging.

A Non-Modifiable Alzheimer’s Risk Factor: Sex

Women get Alzheimer’s at a rate significantly greater than men. Researchers still aren’t sure why. It could be because women tend to live longer, or there may be something in women’s hormones that makes them more susceptible.

A Non-Modifiable Alzheimer’s Risk Factor: Race

Black and Latino Americans have 1.5 to 2 times greater risk of Alzheimer’s diagnosis than white non-Latino Americans. Researchers aren’t sure why that is, but it may have more to do with “the social determinants of health”—income, access to medical care, and other factors—than to do with race per se.

A Semi-Modifiable Alzheimer’s Risk Factor: Injury

People who have suffered injury to their brains through accidents, sports, war, or violence are more likely both to develop amyloid plaques and to be diagnosed with Alzheimer’s.

Air pollution may also be thought of as a form of injury and it, too, is associ­ated with increased risk of plaques and Alzheimer’s.

These are listed as semi-modifiable risk factors because sometimes they can’t be avoided—yet you may be able to lower your risk of exposure by, for example, wearing a helmet while cycling or skiing, using an air filter in your home, or even relocating to a place with better air quality if you have the means to do so.

Modifiable Alzheimer’s Risk Factors

People who have suffered injury to their brains through accidents, sports, war, or violence are more likely both to develop amyloid plaques and to be diagnosed with Alzheimer’s.

Air pollution may also be thought of as a form of injury and it, too, is associ­ated with increased risk of plaques and Alzheimer’s.

These are listed as semi-modifiable risk factors because sometimes they can’t be avoided—yet you may be able to lower your risk of exposure by, for example, wearing a helmet while cycling or skiing, using an air filter in your home, or even relocating to a place with better air quality if you have the means to do so.

1. WE’RE DEALING WITH AVERAGES. Let’s imagine that a study found that participants who engaged in XYZ activity were 15% less likely to develop Alzheimer’s than participants who didn’t engage in the activity. That 15% represents an overall reduction in risk across the group, aggregated from data on many individuals, plenty of whom engaged in the activity yet still got Alzheimer’s. It would be incorrect to come away from such a study and say, “By engaging in XYZ activity, I’ll be reducing my risk of Alzheimer’s by 15%.”
2. WE’RE EXTRAPOLATING FROM SPECIFIC STUDIES. While researchers strive to design studies that will be generalizable to the entire population, this is usually impossible. Study findings pertain only to the type of people (age, sex, health status, etc.) included in the specific piece of research.
3. STILL, FINDINGS MAY BE DIRECTIONALLY ACCURATE. Despite the above two caveats, we can get a good sense of where the overall body of research is pointing us, especially as numerous studies with similar findings start to pile up.

Based on research to date, doctors believe that the following modifiable factors relate to Alzheimer’s risk in some way:

• Physical exercise. Getting your blood pumping on a regular basis has been linked to lower Alzheimer’s risk. Any exercise is better than none, while 2.5 to 5 hours per week of moderate aerobic exercise is recommended.
• Diet. The Mediterranean diet and a variation of it called the MIND diet have been shown to decrease dementia risk. These eating patterns focus on fruits, vegetables, whole grains, fish, nuts, and olive oil, and they steer clear of red meats, sugars, refined carbohydrates, and pro­cessed foods.
• Blood pressure. Hypertension is associated with greater Alzheimer’s risk. Although it may seem like a nonmodifiable risk factor, most people can greatly improve their blood pressure through diet, exer­cise, and medication.
• Oral hygiene. There’s a surprising link between having a healthy mouth and a healthy brain. A 2023 study by Japanese researchers found that people with gum disease saw shrinkage of the hippo­campus, the memory center of the brain that’s usually the first area affected by Alzheimer’s.
• Cholesterol levels. Higher levels of cholesterol, especially during middle age, are associated with increased risk of Alzheimer’s. While statins are effective at lowering cholesterol, it’s not clear that they reduce Alzheimer’s risk. To control your cholesterol, bump up your physical activity and switch from animal fats to monounsaturated fats such as olive oil.
• Social engagement. Becoming socially isolated is a risk factor for dementia. Whether it’s through friends, family, pets, clubs, or church or community groups, staying connected protects your brain.
• Brain exercise. There may be a use-it-or-lose-it effect in play when it comes to brain health. People with more education and more men­tally challenging jobs are at lower risk for Alzheimer’s. Keep your­self mentally stimulated by playing word games, solving puzzles, reading, learning languages, taking courses, and trying new and challenging hobbies.