Houston Methodist. Leading Medicine.
Houston Methodist. Leading Medicine

Nantz National Alzheimer Center

Causes of Alzheimer’s Disease

Although the medical community is still trying to identify the exact cause of Alzheimer's disease (AD) and how to cure the disease, researchers believe that AD may result from a combination of genetics, environment and lifestyle that lead to a cascade of damage to the cells of the brain.


AD tends to strike older people, after the age of 60. More research is needed to study the effects of aging on cognitive decline in the brain.


Researchers have identified several genes that may play a role in the development of AD. One is identified as apolipoprotein E (APOE4), although genetic testing for APOE will not predict whether a person will develop AD. Having this gene or a variant of this gene does not mean a person will get AD, and having no APOE does not guarantee that a patient will remain clear of the disease.

Environment and Lifestyle

Current research shows a link between cognitive decline and vascular and metabolic disorders such as heart disease, hypertension, stroke, diabetes and obesity. More research is needed to better understand these relationships and to determine whether changing these risk factors can affect the development or progression of Alzheimer' s.

We do know that certain characteristics are present in the brains of people with AD. The following physical changes are more common in the brains of people with Alzheimer’s:

  • "Tangles" (Twisted fragments of a protein called tau build up in brain cells.)
  • "Plaques" (Abnormal clusters of beta-amyloid protein form in spaces between the nerve cells.)
  • Loss of neurons, or nerve cells, in the brain
  • Atrophy and shrinkage of the brain

Because of these tangles, plaques and loss of neurons, patients’ brains make fewer connections than healthy brains do. As the brain loses its ability to make connections, it becomes harder to form new memories and access old memories. As more of the brain deteriorates, it becomes harder to perform basic daily tasks of life.