Possible Causes of Alzheimer's Disease

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Male doctor's hand examining sheet of brain MRI scans

Alzheimer’s disease was first recognized in 1906 when a German doctor, Dr. Alois Alzheimer, treated a woman whose memory and behavior had greatly deteriorated over the course of several years. When she died, the doctor discovered dramatic physical changes in her brain: it had shrunk in size and had an abnormal buildup of material in some areas. A few years later, the disease was named after Dr. Alzheimer. More than 100 years later, we know more about what happens to the brain during Alzheimer’s disease, but the cause of this most common form of dementia is still a mystery.

Alzheimer’s—the sixth leading cause of death in the United States--is not a normal part of aging. It has been described as a “cascade” of biological and biochemical changes in the brain. Most people who develop Alzheimer’s disease are diagnosed in their mid-60s or older, but their brains may have been changing for decades. Alzheimer’s disrupts the connections between brain cells, causing the changes in personality and loss of memory. There is a great deal of research underway into Alzheimer’s and currently, experts think the causes are varied and complex. Here are some of the factors that may be involved.

Age-Related Changes

As we age, our brains may shrink, become inflamed or be affected by “free radicals”–molecules known to damage healthy cells. Free radicals are necessary for some bodily functions, but when there are too many of them, they can cause cell death. The brain has two characteristics that may make it particularly susceptible to free radical damage: it has a lot of fatty material and it uses a lot of oxygen. Both factors tend to encourage a buildup of free radical molecules.

Antioxidants counteract free radicals, but there is little evidence so far to suggest that eating foods or taking supplements that contain them can ward off Alzheimer’s, though they can be good for your overall health.

Plaques and Tangles in the Brain

Plaques, the masses of material found in the brains of Alzheimer’s patients, form when pieces of a protein called beta-amyloid stick together in the fatty membrane around nerve cells. They gradually build up into clumps that can block signals from traveling between cells, damaging the ability to remember and think clearly. Tangles are twisted fibers, made up of a protein called tau, that are also found in the brains of Alzheimer’s patients. These tangles damage transportation between cells, preventing them from receiving essential nutrients and supplies, and causing the cells to eventually die. However, researchers don’t know if high levels of beta-amyloid and tau cause Alzheimer’s, or if they are the result of it.


If you have a family history of Alzheimer’s, you are at higher risk of developing the disease. You can be tested for one of the genes that have been linked to Alzheimer’s, APOE-e4, but even if you have the gene, it’s not certain you will develop Alzheimer’s.

There are other genes that do cause Alzheimer’s directly, but they are extremely rare, accounting for only about 5% of cases. These genes cause early-onset Alzheimer’s, the term used when people are diagnosed in their 40s and 50s. Cases of what experts call “familial Alzheimer’s disease” have only been found in a small number of extended families, whom researchers are studying for clues about the disease overall.

Environment and Lifestyle

Experts are looking at factors that may increase the chance of developing Alzheimer’s, such as head trauma—injury to the brain from a car accident, sports, or other impact. They are even studying early life experiences and education levels to see why certain groups of people have a higher incidence of the disease. Other studies are looking at various "lifestyle factors," such as dietary habits, high blood pressure and high cholesterol, to see if they increase the risk of Alzheimer’s disease.

Though the puzzle of Alzheimer’s is far from solved, the clues are being gathered. While we don’t know why it happens, there are treatments and tools that can help overcome some of the ravages of the disease. If you are concerned that you or someone you love may be showing signs, talk to a doctor about getting tested. There are many resources available, including the Alzheimer’s Association, to help families cope with this serious disease.

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Medical Reviewer: William C. Lloyd III, MD, FACS
Last Review Date: 2020 Sep 6
THIS TOOL DOES NOT PROVIDE MEDICAL ADVICE. It is intended for informational purposes only. It is not a substitute for professional medical advice, diagnosis or treatment. Never ignore professional medical advice in seeking treatment because of something you have read on the site. If you think you may have a medical emergency, immediately call your doctor or dial 911.

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