|
Increase size of text: A A A
Introduction
While scientists know Alzheimer’s disease involves
progressive brain cell failure, they have not yet identified
any single reason why cells fail. However, they have identified
certain risk factors that increase the likelihood of developing
Alzheimer’s.
Alzheimer risk factors
Age
The greatest known risk factor for Alzheimer’s is increasing
age. Most individuals with the disease are 65 or older. The
likelihood of developing Alzheimer’s doubles about every
five years after age 65. After age 85, the risk reaches nearly
50 percent.
Family history
Another risk factor is family history. Research has shown
that those who have a parent, brother or sister, or child
with Alzheimer’s are more likely to develop Alzheimer’s.
The risk increases if more than one family member has the
illness. When diseases tend to run in families, either heredity
(genetics) or environmental factors or both may play a role.
Genetics (heredity)
Scientists know genes are involved in Alzheimer’s.
There are two categories of genes that can play a role in
determining whether a person develops a disease. Alzheimer
genes have been found in both categories:
1) Risk genes increase the likelihood of developing
a disease, but do not guarantee it will happen. Scientists
have so far identified one Alzheimer risk gene called apoliprotein
E-e4 (APOE-e4).
APOE-e4 is one of three common forms of the APOE gene;
the others are APOE-e2 and APOE-e3. APOE provides the blueprint
for one of the proteins that carries cholesterol in the
bloodstream.
Everyone inherits a copy of some form of APOE from each
parent. Those who inherit one copy of APOE-e4 have an increased
risk of developing Alzheimer’s. Those who inherit
two copies have an even higher risk, but not a certainty.
Scientists do not yet know how APOE-e4 raises risk. In addition
to raising risk, APOE-e4 may tend to make symptoms appear
at a younger age than usual.
Experts believe there may be as many as a dozen other Alzheimer
risk genes in addition to APOE-e4.
2) Deterministic genes directly cause a disease, guaranteeing
that anyone who inherits them will develop the disorder.
Scientists have found rare genes that directly cause Alzheimer’s
in only a few hundred extended families worldwide.
When Alzheimer’s disease is caused by deterministic
genes, it is called “familial Alzheimer’s disease,”
and many family members in multiple generations are affected.
True familial Alzheimer’s accounts for less than 5
percent of cases.
Genetic tests are available for both APOE-e4 and the rare
genes that directly cause Alzheimer’s. However, health
professionals do not currently recommend routine genetic
testing for Alzheimer’s disease. Testing for APOE-e4
is sometimes included as a part of research studies.
For more information about Alzheimer genetics and an in-depth
discussion of genetic testing, please see our fact sheet
Genes
and Alzheimer’s Disease PDF (3 pages).
Other risk factors
Age, family history and heredity are all risk factors we
can’t change. Now, research is beginning to reveal clues
about other risk factors we may be able to influence.
Head injury: There appears to be a strong link between
serious head injury and future risk of Alzheimer’s.
Protect your head by buckling your seat belt, wearing your
helmet when participating in sports, and “fall-proofing”
your home.
Heart-head connection: Some of the strongest evidence
links brain health to heart health. Your brain is nourished
by one of your body’s richest networks of blood vessels.
Every heartbeat pumps about 20 to 25 percent of your blood
to your head, where brain cells use at least 20 percent of
the food and oxygen your blood carries.
The risk of developing Alzheimer’s or vascular dementia
appears to be increased by many conditions that damage the
heart or blood vessels. These include high blood pressure,
heart disease, stroke, diabetes and high cholesterol. Work
with your doctor to monitor your heart health and treat any
problems that arise.
General healthy aging: Other lines of evidence suggest
that strategies for overall healthy aging may help keep the
brain healthy and may even offer some protection against developing
Alzheimer’s or related diseases. Try to keep your weight
within recommended guidelines, avoid tobacco and excess alcohol,
stay socially connected, and exercise both your body and mind.
For more information about general strategies to support
brain health, please see Alzheimer’s Association (PDF) Maintain Your Brain®.
Vision statement
Back to top
|
