Scientists have identified factors that increase the risk of Alzheimer’s. The most important risk factors—age, family history and heredity—can't be changed, but emerging evidence suggests there may be other factors we can influence.
The greatest known risk factor for Alzheimer’s is increasing age. Most individuals with the disease are 65 and older. One in nine people in this age group and nearly one-third of people age 85 and older have Alzheimer’s.
Another strong risk factor is family history. Those who have a parent, brother or sister with Alzheimer’s are more likely to develop the disease. 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.
Aluminum not a cause
During the 1960s and 1970s, aluminum emerged as a possible suspect in causing Alzheimer’s disease. This suspicion led to concerns about everyday exposure to aluminum through sources such as cooking pots, foil, beverage cans, antacids and antiperspirants. Since then, studies have failed to confirm any role for aluminum in causing Alzheimer’s. Almost all scientists today focus on other areas of research, and few experts believe that everyday sources of aluminum pose any threat.
Learn more: Myths About Alzheimer’s
Scientists know genes are involved in Alzheimer’s. Two categories of genes influence whether a person develops a disease: risk genes and deterministic genes. Alzheimer's genes have been found in both categories.
Genetic testingGenetic 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.
Learn more: Genetic Testing Topic Sheet
- Risk genes increase the likelihood of developing a disease, but do not guarantee it will happen. Researchers have found several genes that increase the risk of Alzheimer’s. apolipoprotein E-e4, or APOE-e4, is the first risk gene identified and remains the one with strongest impact.
Other common forms of the APOE gene are APOE-e2 and APOE-e3. 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. Researchers are not yet certain how APOE-e4 increases risk. In addition to raising risk, APOE-e4 may tend to make Alzheimer's symptoms appear at a younger age than usual.
- Deterministic genes directly cause a disease, guaranteeing that anyone who inherits one will develop the disorder. Scientists have discovered variations that directly cause Alzheimer’s disease in the genes coding three proteins: amyloid precursor protein (APP), presenilin-1 (PS-1) and presenilin-2 (PS-2).
When Alzheimer’s disease is caused by these deterministic variations, it is called “autosomal dominant Alzheimer’s disease (ADAD)” or “familial Alzheimer’s disease,” and many family members in multiple generations are affected. Individuals with these genes usually develop symptoms in their 40s or 50s. Deterministic Alzheimer's variations have been found in only a few hundred extended families worldwide. True familial Alzheimer’s accounts for 1 percent of cases.
The 23 human chromosome pairs contain all of the 30,000 genes that code the biological blueprint for a human being. This interactive illustration highlights the chromosomes containing each of the three genes that cause familial Alzheimer's and the gene with the greatest impact on Alzheimer's risk.
Most experts believe that the majority of Alzheimer's disease occurs as a result of complex interactions among genes and 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 through general lifestyle and wellness choices and effective management of other health conditions.
Head injury: There may be a strong link between serious head injury and future risk of Alzheimer’s, especially when trauma occurs repeatedly or involves loss of consciousness. Protect your brain by buckling your seat belt, wearing your helmet when participating in sports, and “fall-proofing” your home. Learn more about traumatic brain injury.
Heart-head connection: Some of the strongest evidence links brain health to heart health. This connection makes sense, because the brain is nourished by one of the body’s richest networks of blood vessels, and the heart is responsible for pumping blood through these blood vessels to the brain.
The risk of developing Alzheimer’s or vascular dementia appears to be increased by many conditions that damage the heart and blood vessels. These include heart disease, diabetes, stroke, high blood pressure and high cholesterol. Work with your doctor to monitor your heart health and treat any problems that arise.
Studies of donated brain tissue provide additional evidence for the heart-head connection. These studies suggest that plaques and tangles are more likely to cause Alzheimer’s symptoms if strokes or damage to the brain’s blood vessels are also present.
Latinos and African-Americans at risk
Research shows that older Latinos are about one-and-a-half times as likely as older whites to have Alzheimer’s and other dementias, while older African-Americans are about twice as likely to have the disease as older whites. The reason for these differences is not well understood, but researchers believe that higher rates of vascular disease in these groups may also put them at greater risk for developing Alzheimer’s.
Overall healthy aging: One promising line of research suggests that strategies for overall healthy aging may help keep the brain healthy and may even reduce the risk of developing Alzheimer’s. These measures include eating a healthy diet, staying socially active, avoiding tobacco and excess alcohol, and exercising both the body and mind. Sign up for Alzheimer’s enews and stay informed on research investigating lifestyle factors and the risk of cognitive impairment.