Causes

Most people with young-onset Alzheimer's have the most common form of the disease, called sporadic Alzheimer's. This type isn't caused by genetics, and experts don't know why these people get the disease at a younger age than others do.

But others with young-onset Alzheimer's have a type of the disease called familial Alzheimer's disease. They're likely to have a parent or grandparent who also developed Alzheimer's at a younger age.

Young-onset Alzheimer's that runs in families is linked to three genes — the APP, PSEN 1 and PSEN 2 — that differ from the APOE gene that can increase your risk of Alzheimer's in general.

Together, these three genes are present in less than 1% of all people with Alzheimer's but in about 11% of people with young-onset Alzheimer's. If you have a genetic mutation in one of those three genes, you may develop Alzheimer's before age 65.

Genetic testing for these mutations is available, but anyone who's considering it should pursue genetic counseling — to examine the pros and cons before getting tested.

For example, it may be helpful to consider how a positive test may affect your eligibility for long-term care, disability and life insurance.

On the other hand, if you know you carry a form of the young-onset genes, you may be able to take steps to make it easier for you and your loved ones to cope with the effects of the disease.

If you have young-onset Alzheimer's linked to one of the three genes or carry a form of these genes without symptoms, talk to your doctor about participating in a research study. By studying the young-onset form of Alzheimer's, researchers hope to learn more about the causes and progression of the disease and develop new treatments.