People with a gene variant that sharply increases the risk of Alzheimer's disease in old age may show memory impairment earlier than thought -- sometimes well before their 60th birthday, according to new study in the New England Journal of Medicine.



A variant of the APOE gene indicates whether a person has a greater risk of developing Alzheimer's disease.



Between 20 and 35 percent of Americans have one or two copies of this gene variant, inherited from one or both parents. People with one copy of the variant, called apolipoprotein E-e4 (APOE e4), have a 29 percent lifetime risk of developing Alzheimer's disease, while people who don't have it have a 9 percent risk.



People with two copies of APOE e4 have an even higher Alzheimer's risk, but it's hard to define the exact percentage as only 2 percent of the population falls into this category.



Despite the gene-related health problems, another study in the same issue of the journal suggests that people who learn they do have APOE e4 seem to handle the information pretty well. But the researchers excluded people with anxiety or depression, and they followed people for just a year.



Therefore, the results don't tell the whole story about what it would be like for most people to find out whether they carried the APOE e4 gene. Nevertheless, the findings are an important first step, said Dr. Kenneth Kosik, a professor of neuroscience at the University of California Santa Barbara and the codirector of UCSB's Neuroscience Research Institute.



"I think it opens the door to ask the deeper questions," said Kosik, referring to the possible consequences for individuals and society if widespread APOE testing were introduced. (Kosik was not involved with either study.)



If people do find out they have the APOE e4 gene, Kosik added, the new memory study could make the news harder to bear.



Dr. Richard J. Caselli, of the Mayo Clinic Arizona, in Scottsdale, and his colleagues followed 815 people ages 21 to 97 with normal mental function, including 317 who had at least one copy of the APOE e4 gene. On one test of a person's ability to learn and remember (the Auditory-Verbal Learning Test) gene carriers showed declines in their scores beginning in their 50s. For people without the APOE e4 gene, this decline started in their 70s.



"We're not talking anymore about a retired population; we're talking about people who will be in the midst of their career," Caselli said. He added that many would be in positions of responsibility in which they need to have all their wits about them -- and they may not. Health.com: Eat smarter in your 30s, 40s, and 50s



"[The study] forces us to really think about the brave new world of genetics," and how this information might be used, Kosik said. Although there had been a "clear line" between having the APOE e4 gene but being dementia-free and having Alzheimer's disease, that distinction isn't as clear anymore, he explained.



For someone who discovers he or she has the APOE e4 gene, Caselli said, "The only advice I have is, 'Don't panic.'"



Right now, APOE gene testing is only recommended for people with mild problems with mental function or dementia; for people with no symptoms, it should only be done in a research setting, experts said. Nevertheless, labs have sprung up that will offer the "worried well" an APOE gene test for a fee.



Having APOE testing without adequate medical, psychological, or genetic counseling is "inappropriate," said Dr. Hyman Schipper, a professor of neurology and medicine at McGill University, and the director of the Centre for Neurotranslational Research at SMBD--Jewish General Hospital, both in Montreal. In these situations, Schipper explained people may not interpret the results correctly, and could run the risk of psychological harm.



For example, people who find out they carry the gene for Huntington's disease -- which means they have a 100 percent chance of developing a devastating neurodegenerative condition if they live long enough --
Who is testing recommended for? What test is recommended for mild mental function? how many people have alzheimer What means  a 29% chance of Alzheimers What happens to people with the gene? Which group showed declines in their 50's? What does the gene variant mean?
people with mild problems with mental function or dementia; APOE gene testing Between 20 and 35 percent of Americans People with one copy of the variant, called apolipoprotein E-e4 (APOE e4), increases the risk of Alzheimer's disease gene carriers 29 percent lifetime risk of developing Alzheimer's disease,
question: Who is testing recommended for?, answer: people with mild problems with mental function or dementia; | question: What test is recommended for mild mental function?, answer: APOE gene testing | question: how many people have alzheimer, answer: Between 20 and 35 percent of Americans | question: What means  a 29% chance of Alzheimers, answer: People with one copy of the variant, called apolipoprotein E-e4 (APOE e4), | question: What happens to people with the gene?, answer: increases the risk of Alzheimer's disease | question: Which group showed declines in their 50's?, answer: gene carriers | question: What does the gene variant mean?, answer: 29 percent lifetime risk of developing Alzheimer's disease,