The Alzheimer’s Gene: would you want to know?

One of the most popular carnival attractions is the Fortune Teller tent.  People line up, take $5 out of their pockets and hope for a glimpse into their future.  Some want to know if they are in the right career, others want to know if their relationship will last, if they will come into money of if they will have children. How many, I wonder, want to know if they will develop a disease for which there is no cure?

Genetic testing may allow them to do just that.  Scientists have recently discovered five gene variants that raise the risk of developing Alzheimer’s disease. While the test is now available to curious individuals with a family history of the disease, the question remains would you want to know?

The five gene markers were discovered after scientists compared the genetic makeup of tens of thousands of patients with those of healthy volunteers.  The discovery of these five genes put the total number of genes linked to Alzheimer’s disease at ten.

Genes account for 60 to 80 percent of an individual’s chance of developing late-onset Alzheimer’s.  The remainder of the risk results from lifestyle and environmental factors such as education, social engagement and diet as well as other health factors including hypertension, diabetes and hypercholesterolemia.  These additional causative factors can influence whether an individual will develop the disease later in life, regardless of family history of the disease.

Family history, though, is an important causative factor influencing an individual’s pre-disposition to the disease.  Having a first degree relative with late-onset Alzheimer’s increases an individual’s risk of developing the disease to 17%, relative to approximately 5% in an individual with no family history of the disease. 

In families where an affected person is in their 50s or 60s at the onset of the disease, genetic factors become more influential.  If multiple family members have been affected, genetic testing may be used to identify gene mutations. 

This latest research into Alzheimer’s genetic testing is the result of two studies published in Nature Genetics.  The first study was led by Julie Williams at Cardiff University’s MRC Centre for Neuropsychiatric Genetics, and the second by Gerard Schellenberg at the University of Pennsylvania School of Medicine in Philadelphia.

The discovery of these five new genes has created a picture of Alzheimer’s disease as one driven by genetic factors that, through the course of one’s lifetime, build up and ultimately cause the steady and irreversible destruction of brain cells.

Eliminating the detrimental effects of all ten genetic variants discovered to date would potentially eliminate 60 to 80% of Alzheimer’s disease. The latest research into these genetic markers point scientists in the right direction.  By understanding how genes cause the disease, they can identify drugs and or lifestyle changes that can counteract their negative effects and potentially delay the onset of the disease.

The benefits of this research to scientists is clear, but the results also have implications to individuals who may be able to use this genome information to determine whether they have the genetic markers that predispose them to the disease. 

At present, there is a test for the ApoE-e4 gene, which can help determine if an individual will develop late-onset Alzheimer’s.

The ability to provide this knowledge to individuals is groundbreaking, but what are the negative effects of having this much knowledge? 

While predictive genetic testing may be an option considered by individuals in families with a history of the disease, the decision to undergo the test is highly controversial.  The test results may affect individuals’ long term decision making regarding personal relationships, having children, financial and lifestyle choices.  

Deciding to take the test can have profound effects on the family dynamic.  Genetic markers are familial.  While one member of the family may want to know what lies ahead, others may be fearful of receiving such information.  If one family member takes the test, their results may reveal genetic information about other members of the family who may want to be sheltered from this information about themselves. 

In addition to these personal lifestyle and family decisions, there are a number of other factors to consider before taking the test, such as how the results can affect insurance and employment benefits.

Knowing your predisposition to developing a disease for which there is currently no cure or prevention can be a difficult decision that can affect how an individual views their life. 

Understanding the risks is tricky business.  It’s recommended that individuals looking to have the test receive counseling so they properly understand the implications of the test results.  Having a positive gene marker does not mean that the individual will necessarily develop the disease.  People who inherit a single copy of the ApoE-e4 gene are at an increased risk of developing Alzheimer’s disease as they age, while individuals who inherit two copies of the gene are placed at very high risk, but even individuals without the gene may still be at risk. 

Robert C. Green, MD, co-director of the Boston University Alzheimer’s disease program wanted to determine the psychological effects that taking the test would have on individuals.  The general assumption among the medical community has been that taking the test would result in psychological problems that stemmed from patients not understanding the concept of the risk gene and automatically assuming that if they had the gene, they would develop Alzheimer’s. Many physicians have taken the position that the test should not be recommended for asymptomatic patients.  The reason being that the results of the test will become part of the individual’s medical record and at this point in medical history, there is nothing that can be done about it. 

Green’s study included results collected by Alzheimer’s researchers from across Canada and the United States.  They recruited 162 mentally healthy individuals in their 50s with a parent who had Alzheimer’s disease.  None of the participants had any symptoms of the disease and all were willing to get the ApoE test, even though they knew they might not learn the results of the test. 

Researchers disclosed the results of the test to two-thirds of the participants and then conducted a series of psychological tests with all participants over the next year.

Those who learned the result of their test, even if they learned they had the predictive gene, did not suffer any more anxiety or depression than the group that did not learn their test results.

Six weeks after learning their results, those who learned they had the gene suffered a bit more distress, but got over it, and those who learned they did not carry the gene predictably felt a sense of relief.

With the technology available to find genetic markers, it’s every individual’s choice to use the information available to attempt to predict their future mental health.  Proper consultation to understand the pros and cons of learning the results including legal, medical, and psychological concerns should be undergone by every individual seeking to pop their bucks in the genetic fortune teller’s box.