What is Alzheimer's, and who's at risk?
The following questions are based on the known risk factors for Alzheimer's. See how many apply to your family (or to you, to assess your risk of eventually developing the disease).
1. How old is he or she?
- At lower risk: Under age 70
- At higher risk: Over age 85
The total number of people with the disease doubles with every five-year age jump after age 65.
2. Is it a he or a she?
- At lower risk: Men
- At higher risk: Women
Why gender matters: Because women live longer than men, on average, and Alzheimer's disease risk rises with age, more women than men develop it. In addition, some research indicates that a lack of estrogen after menopause may contribute to the fact that, overall, slightly more women are affected. Taking hormone-replacement therapy has not been shown to protect against Alzheimer's.
Vascular dementia is more common in men than women, probably because more men develop contributing factors such as hypertension and vascular problems.
3. Have any of his or her parents or siblings had Alzheimer's?
- At lower risk: No family history or known genetic predisposition
- At higher risk: A family history or known genetic predisposition
It's unknown, though, exactly how much of this association is due to genetic factors and how much is due to shared lifestyle factors. Most experts believe that some combination of the two is responsible. Even when an immediate family member has the disease, however, your increased risk is only slightly higher than if your family had no history of dementia.
Up to 80 percent of Alzheimer's risk may have a genetic component, according to a 2006 study of more than 12,000 Swedish twin sets -- a greater influence than was previously thought. But having a relative with the disease does not doom a person to a similar fate; even among identical twins, when one male twin had it, almost half of the time the other twin did not. (Among female twins, the other twin developed Alzheimer's 60 percent of the time, a difference researchers attributed to the fact that women generally live longer than men.) If Alzheimer's were solely genetic, both twins would have developed the disease, and at about the same time.
So far, only two types of genetic tests for Alzheimer's exist, and neither of these blood tests is currently recommended for routine use.
- One kind of genetic test identifies a person's risk of developing Alzheimer's disease but doesn't guarantee whether or not he'll develop the condition. Everyone inherits a form of the apolipoprotein (APOE) gene from each parent. Apolipoprotein helps carry cholesterol in the blood. Its three most common forms are APOE-e2, APOE-e3, and APOE-e4. Those who have two copies of APOE-e4 seem to be at the highest risk of getting Alzheimer's and of developing symptoms earlier in life. Having one copy of APOE-e4 also elevates the risk. Only about 15 percent of people carry the APOE-e4 form.
- A second type of existing genetic test for Alzheimer's disease can predict with certainty who develops one rare form of the disease. This is early-onset familial Alzheimer's disease, which strikes between the ages of 30 and 65 and stretches through multiple generations. It accounts for less than 5 percent of all cases.
Does he or she smoke?
- At lower risk: Nonsmokers, former smokers
- At higher risk: Current smokers
It's thought that smoking damages the cardiovascular system and causes oxidative stress, both conditions that are associated with Alzheimer's.
You may have heard that smoking protects against dementia -- which is a myth. This persistent idea grew out of flawed studies and because fewer people with Alzheimer's were smokers. But in fact smokers, tend to have shorter life spans and are less likely to live to the advanced ages at which Alzheimer's most often strikes.
5. Does he or she have diabetes?
- At lower risk: No history of diabetes
- At higher risk: Those with type 2 diabetes
The mechanics behind the Alzheimer's-diabetes link aren't certain, but this is an area of intensive research. The leading explanations:
- High blood sugar may cause vascular problems. It's known that diabetes can cause cardiovascular problems and strokes; reduced blood flow to the brain may cause small-vessel damage there that leads to vascular dementia (a type of dementia that can appear with Alzheimer's).
- Insulin resistance leads to inflammation that can damage the brain. Insulin resistance occurs in diabetics when their cells can't use insulin properly to move glucose from the blood to be used for cell energy. The pancreas then makes extra insulin to compensate, which builds up in the blood and creates inflammation, which damages brain cells.
- Insulin resistance in the brain disrupts the proper formation of neuron connections. The autopsied brains of people with Alzheimer's always show amyloid plaques, clumps of the protein beta amyloid, which ruin brain cell connections. It's been discovered that this substance destroys the brain cells' receptors for insulin, which is used by the brain to make new memories. This results in dementia and memory loss.
There's also a likely genetic link between diabetes and Alzheimer's. People with diabetes who also have the APOE-e4 gene (the type that places a carrier at highest risk for Alzheimer's) were two-and-a-half times more likely to develop the disease, according to a 2008 National Institute on Aging study.
6. Does he or she have a history of being overweight?
- At lower risk: Low BMI in midlife
- At higher risk: Overweight or obese in midlife
People who are overweight are more likely to have related health problems that are also linked to Alzheimer's, such as hypertension, high blood pressure, cardiovascular disease, and diabetes.
A related risk factor is if someone was previously overweight but has had unexplained weight loss recently. Weight loss associated with dementia may begin six to ten years before other symptoms become obvious. Research isn't clear whether this is because of declining ability to prepare meals or is a function of the disease process.
Who Gets ItAt lower risk: No injury At higher risk: Prior head injury, especially after age 50
Why head injury matters: Prior head injury -- even years earlier -- is linked with a greater risk of developing Alzheimer's, though it's not clear why. That's not to say that any youthful bump will lead to Alzheimer's. The injury itself isn't thought to directly cause the disease, although it may hasten the process. But the more severe the trauma, the greater the risk of developing Alzheimer's, according to a large study of World War II veterans. The most concerning are thought to be falls with head injuries that occur later in life.
8. Was he or she a college graduate?
- At lower risk: Higher education level
- At higher risk: Lower education level
9. Does he or she consume a balanced, low-fat, vitamin-rich diet?
- At lower risk: Heart-healthy diet rich in antioxidants
- At higher risk: Eating high-fat foods and an unbalanced diet
- B vitamins: People who are folate (B-9) deficient may run triple the risk of developing dementia, according to recent South Korean data. Previous research showed vitamin B-12 to be protective.
- Vitamin E: Those who consume the highest dietary amounts of this antioxidant have a lower incidence of Alzheimer's. Vitamin E supplements have not been shown to have the same protective effect.
- Vitamin C: Another antioxidant, vitamin C, seems to have a protective effect in certain people, though possibly only in dietary form. Antioxidants counter the effects of oxidative stress, which is linked to nerve cell damage and death. Over-the-counter vitamin C supplements did not reduce Alzheimer's risk in a recent study of 2,969 people 65 and older.
- A heart-healthy diet: People who consume a generally balanced diet that avoids too much fat and includes complex carbohydrates are less likely to develop conditions that are Alzheimer's risks, including obesity, diabetes, and cardiovascular disease
- 10. Does he or she exercise regularly?
- At lower risk: Active lifestyle
- At higher risk: Sedentary lifestyle
Previous research has shown that the variety of activity engaged in is more important than the intensity of a workout, when it comes to providing brain benefits. (Variety of workouts had no benefit, though, to those with the APOE-e4 gene variation most commonly associated with Alzheimer's.)
11. Does he or she engage in mentally stimulating activities?
- At lower risk: Varied, frequent "brain workouts"
- At higher risk: Lack of mental stimulation
Brain-stretching activities can't prevent Alzheimer's, but they help the brain better withstand the physical changes associated with it. What's key: The stimulation should be ongoing.
12. Is he or she socially stimulated?
- At lower risk: Social engagement
- At higher risk: Social isolation and loneliness
- This article was presented from:
- Paula Spencer Scott, Caring.com contributing editor Paula Spencer Scott, contributing editor, is the author of Surviving Alzheimer's. A Met Life Foundation Journalists in Aging fellow, she writes extensively about health and caregiving; four of her family members have had dementia.