Gene is marker only for mild cognitive impairment

February 12, 2013 by Susan Kelley
Credit: Jennifer Infante

Defying the widely held belief that a specific gene is the biggest risk factor for Alzheimer's disease, two Cornell developmental psychologists and their colleagues report that people with that gene are more likely to develop mild cognitive impairment—but not Alzheimer's.

The study suggests that older adults with healthy can get genetic tests to predict increased risk of future . However, once they are impaired cognitively, the tests won't predict their of developing 's.

"Right now, genetic tests are used in exactly the opposite way. That is, healthy people don't get the tests to predict their risk of mild , but impaired people get them to predict their risk of Alzheimer's disease," said Charles Brainerd, professor of human development and the study's lead co-author with Valerie Reyna, professor of human development. "So, impaired people think that tests will tell them if they are at increased risk of Alzheimer's, which they won't. And healthy people think that tests won't tell them whether they are at increased risk of cognitive impairment, which they will."

The researchers describe their findings in the January issue of Neuropsychology.

The work builds on previous research by Brainerd and associates that suggested the ε4 allele of the increases the risk of mild cognitive impairment as well as Alzheimer's.

The researchers analyzed data from the only nationally representative dataset of its kind, the National Institute on Aging's Aging, and Memory Study. They looked at data from 418 people over age 70 to see if those who carried the allele were more likely to develop mild cognitive impairment compared with those who did not have the allele. They also looked at whether ε4 carriers with mild cognitive impairment were more likely to develop Alzheimer's disease compared with non-carriers with mild cognitive impairment.

They found that healthy ε4 carriers were nearly three times—58 percent—more likely to develop mild cognitive impairment compared with non-carriers. However, ε4 carriers with mild cognitive impairment developed Alzheimer's at the same rate as non-carriers.

While previous studies showed that the ε4 allele was more common in people with Alzheimer's disease, this study shows that it does not increase the risk that healthy or impaired people will become demented. Rather, ε4 increases the risk that healthy people will become cognitively impaired, and impaired people are the primary source of new Alzheimer's diagnoses, Brainerd explained. "The reason ε4 is a risk factor for mild cognitive impairment, but not for progression from mild cognitive impairment to Alzheimer's disease, is that this allele is a marker of initial cognitive declines—for example, memory and executive function—that are associated with mild cognitive impairment but not of subsequent declines in cognition or in daily functioning that are associated with forms of Alzheimer's disease."

Brainerd also noted that the effects of ε4 in healthy adults can be detected by the mid-20s. While ε4 is not a risk factor for the severe cognitive declines that signal dementia, it is risk factor for the weaker declines that eventually produce mild cognitive impairment.

Explore further: Cardiac disease linked to higher risk of mental impairment

Related Stories

Cardiac disease linked to higher risk of mental impairment

January 28, 2013
Cardiac disease is associated with increased risk of mild cognitive impairment such as problems with language, thinking and judgment—particularly among women with heart disease, a Mayo Clinic study shows. Known as nonamnestic ...

Plaque build-up in your brain may be more harmful than having Alzheimer's gene

October 15, 2012
A new study shows that having a high amount of beta amyloid or "plaques" in the brain associated with Alzheimer's disease may cause steeper memory decline in mentally healthy older people than does having the APOE ɛ4 allele, ...

Recommended for you

Lifestyle changes to stave off Alzheimer's? Hints, no proof

July 20, 2017
There are no proven ways to stave off Alzheimer's, but a new report raises the prospect that avoiding nine key risks starting in childhood just might delay or even prevent about a third of dementia cases around the world.

Blood test identifies key Alzheimer's marker

July 19, 2017
A new study led by researchers at Washington University School of Medicine in St. Louis suggests that measures of amyloid beta in the blood have the potential to help identify people with altered levels of amyloid in their ...

Steering an enzyme's 'scissors' shows potential for stopping Alzheimer's disease

July 19, 2017
The old real estate adage about "location, location, location" might also apply to the biochemical genesis of Alzheimer's disease, according to new research from the University of British Columbia.

Brain scans may change care for some people with memory loss

July 19, 2017
Does it really take an expensive brain scan to diagnose Alzheimer's? Not everybody needs one but new research suggests that for a surprising number of patients whose memory problems are hard to pin down, PET scans may lead ...

Can poor sleep boost odds for Alzheimer's?

July 18, 2017
(HealthDay)— Breathing problems during sleep may signal an increased risk for Alzheimer's disease, a trio of studies suggests.

Hearing is believing: Speech may be a clue to mental decline

July 17, 2017
Your speech may, um, help reveal if you're uh ... developing thinking problems. More pauses, filler words and other verbal changes might be an early sign of mental decline, which can lead to Alzheimer's disease, a study suggests.

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.