Risk for Alzheimer’s disease increases greatly with age. At age 65, the risk of developing Alzheimer’s doubles roughly every five years, reaching almost fifty percent by age 85.

Alzheimer’s disease has no known cure. The few medications that are available help to lessen some symptoms of the disease and provide temporary, partial relief-but having no real effect on cognitive decline. Currently, there are no medications that can stop the progression of the disease.


A complicating factor for researchers is that there is no known single cause of Alzheimer’s disease. However, many risk factors have been identified.


Genetics appears to play an important role in Alzheimer’s disease; we now know several genes that increase the risk of-or protect against-the disease.

It is also documented that Alzheimer’s can run in families. For example, inheriting one copy of the APOE4 gene variant (which is found in about 20% of the population) will cause up to 4X the normal risk of developing Alzheimer’s disease. Inheriting two copies of APOE4 (one from each parent) will dramatically raise the risk: up to 10X normal levels. But, having a family member with Alzheimer’s disease is not a guarantee of developing the disease.

Known genetic factors account for a small percentage of all Alzheimer’s disease cases, but current research supported by Cure Alzheimer’s Fund indicates far more genetic influence than was previously known. Many candidate genes are currently being discovered and studied for their role in the disease. The genes we know about account for a large percentage of early-onset cases. The rare Presenilin 1 and 2 genes, for instance, virtually guarantee development of early-onset Alzheimer’s.

Individuals with Down syndrome almost always develop early-onset Alzheimer’s disease. Down syndrome occurs in those carrying an extra copy of chromosome 21. This chromosome happens to include the APP gene, which controls Abeta production, a major factor in Alzheimer’s disease pathology.

Increased Risk of Developing Alzheimer's disease Based on Ingeriting APE4 Gene Variant from One Parent vs. Both

Of all the risk factors, age is most significant for developing Alzheimer’s disease. After age 65, the risk tends to double about every five years, reaching almost 50 percent by age 85. In a lower percentage of the population, the disease can begin earlier in life.

Another risk factor is assigned sex: Women develop Alzheimer’s disease at twice the rate of men. The reasons behind this are not understood: Cure Alzheimer’s Fund is investing in research to determine the factors influencing sex-based differences.

Sleep patterns also appear to influence the pathology of the disease. With age, the sleep/wake cycle can break down causing older adults to get less sleep. Investigators are considering studies of whether chronic sleep loss in young and middle-aged adults increases risk of Alzheimer’s disease later in life. David Holtzman, M.D., an Alzheimer’s researcher from Washington University in St. Louis, has demonstrated that when the genes that regulate sleep/wake cycles are deleted in mice, the result is cognitive decline.

 

From the National Institutes of Health and the National Institute on Aging:

“Research suggests that a host of factors beyond genetics may play a role in the development and course of Alzheimer’s disease. There is a great deal of interest, for example, in the relationship between cognitive decline and vascular conditions such as heart disease, stroke, and high blood pressure, as well as metabolic conditions such as diabetes and obesity. Ongoing research will help us understand whether and how reducing risk factors for these conditions may also reduce the risk of Alzheimer’s.”