The decision to get tested for Alzheimer’s disease is very personal. If someone is already showing symptoms, medication and behavior modification can assist with those symptoms. But if no symptoms are evident, the knowledge of a genetic link to Alzheimer’s may offer little reassurance that the disease is or is not in their future.
Testing for Alzheimer’s is complicated because there is so much uncertainty surrounding this disease. It’s believed as of this writing that Alzheimer’s is caused by either genetics, lifestyle, or a combination of the two.
Family members of a loved one of Alzheimer’s often fear they too may succumb to the disease. But scientists have yet to fully understand the genetics involved. What they do believe at this point is that there are four mutations of genes associated with Alzheimer’s that are of greatest concern. Three of these genes (located on chromosomes 21, 14, and 1) are linked to the early-onset forms which may show symptoms when the carrier is in their early 40s or 50s. This form is rare, but if acquired, is likely to manifest into the disease.
Genes are divided into two major categories which include risk genes and deterministic genes.
There are more than 100 risk genes that increase the likelihood of developing late-onset Alzheimer’s disease. The gene with the greatest risk is APOE-e4 on chromosome 19. People with one copy have about three times the risk of getting Alzheimer’s than those with other forms of genes. Those with two copies have an even greater risk. However, multiple copies do not guarantee that someone will definitely develop the disease.
Deterministic genes directly cause a disease. If someone inherits these genes, they will develop the disorder at the estimated age of onset. Only a small minority of Alzheimer’s disease cases are caused by deterministic genes which typically are in the form of early-onset.
Current diagnosis of Alzheimer’s consists predominately of documenting mental decline and ruling out other causes for that decline. Research shows that those with mild cognitive impairment have a significantly increased risk of developing Alzheimer’s disease within a few years. You can find the 10 Warning Signs of Alzheimer’s disease on the Alzheimer’s Association’s website.
A genetic test is available for 10 diseases or conditions, which does include the APOE-e4 Alzheimer’s risk gene. The Alzheimer’s Association strongly recommends that people receive genetic counseling before a test is ordered and when the results are obtained.
Neuroimaging offers some indication of the disease, as well. Magnetic resonance imaging (MRI) and computed tomography (CT) help to rule out other causes of mental impairment such as tumors, evidence of strokes, damage from head trauma or buildup of fluid in the brain. Position emission tomography (PET) brain scans also can help identify beta-amyloid in the brain.
These tests do present some challenges, however. Analysis of protein levels in the same sample often varies significantly from one institution to another. A standard protocol has yet to be established.
Before testing, one should consider the effect of knowing the results. An indication of the genetic component doesn’t guarantee the disease will manifest in the individual’s lifetime and those who do not have a genetic component may still develop it. If the results indicate Alzheimer’s the knowledge could impact one’s personal life, employment, and insurance availability
As of this writing, there is no known intervention to prevent, slow, or stop Alzheimer’s disease. Our best prevention is in regards to lifestyle: exercise, maintain a healthy diet, stop smoking, limit alcohol consumption, stimulate the mind with formal education, reduce weight, monitor blood pressure, control diabetes, prevent head injury, get enough sleep, treat depression and anxiety, and keep socially engaged.