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 do n'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 do n'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 is n'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 , 'Do n'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 -- do indeed experience anxiety , depression , and suicidal thoughts , Schipper noted . Health.com : Fight aging -- the real secrets to staying young . In the second study , Dr. Robert C. Green of the Boston University School of Medicine , and his colleagues in the REVEAL Study Group set out to look at whether something similar would happen to people who found out they carried the Alzheimer 's gene . They assigned 162 symptom-free people at random to a group who would receive their APOE genotyping results and a group who would not be told their results , and then checked their level of anxiety and depression -- as well as stress related to the gene test -- six weeks , six months , and one year after they got the news ( or did n't ) . All of the study participants had a parent with Alzheimer 's disease , but none of them had any signs of mental impairment or dementia . People who found out they did n't carry the gene variant were less stressed about the test than those who found out they did carry the gene . Green and his team also found that the higher a person scored on initial tests of anxiety and depression symptoms , the more likely he or she was to be anxious or depressed after finding out about the gene , although the researchers had excluded people with severe anxiety or depression from the study . However , there were no differences between the groups that were told the news and those who were not . The fact that people in the study agreed to be randomly assigned to get their APOE results suggests they `` are not representative of those who have a strong perceived need to know or need not to know , '' Rosalie A. Kane and Dr. Robert L. Kane of the University of Minnesota , in Minneapolis , wrote in an editorial published with the studies . The study also considered only the psychological impact of the news , they say . Some people might make major life decisions based on the news , such as deciding to hoard their money or spend it all . In addition , employers and health insurers are banned from discriminating against someone based on their genes , but companies offering long-term-care insurance , disability insurance , and life insurance are allowed to take this information into account . Health.com : How to get your way with body language . One major reason why learning APOE e4 status could be so stressful is that there 's no clear way to reduce Alzheimer 's risk . But there could be soon , some experts say . `` We do n't know yet how by doing interventions whether or not we can beat the APOE gene or at least diminish its effects , '' said Kosik . `` We do know that the likelihood of getting Alzheimer 's disease is very much affected by people 's exercise level , their blood pressure , their cholesterol levels , perhaps their diet , and the degree to which they engage in cognitive challenges . All of those things have data , some stronger than others , that you can have some effect on your likelihood of getting Alzheimer 's . '' But , Caselli points out that trying to encourage people to exercise in order to prevent heart disease , for example , has been far from successful , and getting people to be active to ward off Alzheimer 's may be equally difficult . Health.com : Heartburn or heart attack ? How to tell the difference . Maybe , however , the thought of losing our minds is a bit more motivating than the idea of heart disease . `` There is some recent evidence to suggest , in fact , that personal knowledge of APOE status and general AD risk profile may spur healthy midlife adults to adopt or modify behaviors that might protect against the disease , '' Schipper said . Health.com : 10 Risk factors for heart disease . Apolipoprotein is a cholesterol-carrying molecule , and the gene that makes the protein comes in three slightly different versions -- e2 , e3 , and e4 ( there 's no e1 ) . In addition to increasing the risk of Alzheimer 's disease , APOE e4 is also associated with a greater risk of heart disease . Enter to win a monthly Room Makeover Giveaway from MyHomeIdeas.com . Copyright Health Magazine 2009 .
Having this type of gene variant , APOE e4 , increases 1 % risk of Alzheimer 's . People with APOE e4 gene variant show declines beginning in their 50s . APOE gene therapy is only recommended for people with mild mental functions .