They do know that people with a certain form of the gene Apolipoprotein E–ApoE4–are much more likely to get Alzheimer’s. They also know that people who suffer from the disease tend to have measurably lower activity in specific areas of the brain. Now a group of researchers has found that middle-aged people with two copies of the ApoE4 gene type but no symptoms of the disease show lower activity in the same areas as people with Alzheimer’s. This could be a sign of the disease’s beginnings.
In last week’s New England Journal of Medicine, the researchers described how they made their findings with Positron Emission Tomography. PET reveals brain activity by lighting up the local metabolism of glucose. The team found regions of low activity in the brains of 11 people between the ages of 50 and 62, all with two copies of the ApoE4 gene form and a family history of Alzheimer’s but no cognitive signs of the disease. They compared those results with a similar study of patients diagnosed as having Alzheimer’s, and found that many of the reduced-activity regions overlapped.
It’s no real surprise. Alzheimer’s begins long before a doctor’s diagnosis. The real significance of the study is the possibility that doctors might identify Alzheimer’s before it does any damage, and perhaps improve their ability to treat it. “We would like to be able to provide a clue to see if people are on the right track [for therapy] without having to wait a generation,” says Eric Reiman, a psychiatrist at Good Samaritan Regional Medical Center in Phoenix, Ariz., and the lead author of the study.
The chance that Alzheimer’s might be diagnosed early, and its progress monitored, has researchers excited. “The aim is to make the diagnosis earlier and earlier,” said John Hardy, a geneticist at the University of South Florida who studies Alzheimer’s but wasn’t involved in this work. “That’s going to be important when we get treatments, because all of them are designed to stop the disease, not reverse it.”
Reiman’s work is not over. His group will have to follow the people they test-ed for years to confirm their findings. And other areas of reduced function in the ApoE4 group’s brains, he reports, don’t overlap with those of Alzheimer’s patients. That suggests that the gene has other age-related effects, apart from its link to Alzheimer’s, that need further study. But PET scans may give researchers a major advantage in their fight against Alzheimer’s: now they can see the Great Eraser before it even hits the page.
