What Causes Alzheimer's Disease? | Alzheimer's Association

Causes and Risk Factors for Alzheimer's Disease
Researchers believe there isn't a single cause of Alzheimer's disease. It likely develops from multiple factors, such as genetics, lifestyle and environment. Scientists have identified factors that increase the risk of Alzheimer’s. While some risk factors — age, family history and heredity — can't be changed, emerging evidence suggests there may be other factors we can influence.
Age
The greatest known risk factor for Alzheimer’s and other dementias is increasing age, but these disorders are not a normal part of aging. While age increases risk, it is not a direct cause of Alzheimer's.
Most individuals with the disease are 65 and older. After age 65, the risk of Alzheimer's doubles every five years. After age 85, the risk reaches nearly one-third.
Family history
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), 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.
Genetics (heredity)
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. It is estimated that less than 1% of Alzheimer’s cases are caused by deterministic genes (genes that cause a disease, rather than increase the risk of developing a disease).
Other risk factors you may be able to influence
While age, family history and heredity are all risk factors we can’t change, 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.
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Head injury: There is a link between head injury and future risk of dementia. 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.
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 and other dementias. These measures include eating a healthy diet, staying socially active, avoiding tobacco and excess alcohol, and exercising both the body and mind.
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.