According to new study in the New England Journal of Medicine, people with a gene variant that sharply increases the risk of Alzheimer’s disease in old age may show memory impairment earlier than thought.

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.