In order to address this, Bateman says that the DIAN researchers will try to use drugs to stop the accretion of amyloid in people with the Alzheimer’s gene who haven’t yet shown symptoms. The study is building on others that followed middle-aged subjects for years, watching for early signs in the brains of those who eventually develop Alzheimer’s.

One study in particular has been helpful. It’s called ADNI (Alzheimer’s Disease Neuroimaging Initiative), and it began in October 2004. ADNI includes 200 people whose memories are normal, 400 with mild memory problems that might be harbingers of Alzheimer’s disease and 200 with Alzheimer’s disease. Researchers regularly give these subjects memory tests and do brain imaging and other tests to watch for the progress of Alzheimer’s. The study found that characteristic brain changes — shrinkage of the memory center, beta amyloid plaques, excessive synthesis of beta amyloid and tau — arise more than a decade before a person has symptoms.

The first phase of the DIAN study also looks at the progression of Alzheimer’s in the brain, but using only subjects who are members of families with Alzheimer’s genes. When these people join DIAN, Bateman and his colleagues test their memory and reasoning as well as administer spinal taps and scans to monitor changes in their brains. The researchers test the subjects every one to three years, and they have found that they can see troubling brain changes in people with the gene as many as 20 years before they would be expected to show symptoms based on their parent’s age when the disease was first diagnosed. Given the results from DIAN and other studies, Bateman concluded that the ideal time to give an experimental drug is within 15 years of the suspected onset.

Before they could begin testing drugs on people with an Alzheimer’s gene, though, the researchers had to solve a delicate problem. DIAN participants are aware that they have a fifty-fifty chance of possessing an Alzheimer’s gene, and they know they can be tested and find out if they inherited it — but almost no one wants to know. The researchers can give the drugs only to people who have the gene, however. (You don’t want to give a drug that affects the brain to healthy people.) If the study took only people with the gene, all those who were accepted would know that they had it. In order to avoid this problem, the DIAN researchers are inviting members of families with one of the mutated genes to join, regardless of whether the individuals know they possess the gene. Subjects won’t know which group they are in, but the researchers will know, and they will assign those who don’t have an Alzheimer’s gene to the placebo group. The participants with the gene will be randomly assigned to receive one of three experimental drugs or a placebo. The researchers say that within two years, they will have an indication about whether any of the drugs are working.

Bateman explained that the next step in Alzheimer’s research would be to study people who do not have the gene. The idea would be to look at, say, 70-year-olds who seem cognitively normal but who are at an age where Alzheimer’s is increasingly likely. Those subjects would be given scans and other tests to see whether, despite the absence of symptoms, their brains showed changes consistent with the beginning of Alzheimer’s. They would then be enrolled in a drug study. If the drug were to prevent the disease in these people, researchers predict that tests for beta amalyoid plaques might become a recommended preventive medical procedure. People might be tested at age 50 and periodically afterward. Anyone getting plaques would take the drug to prevent Alzheimer’s disease.

In 1995, the same year that Bird discovered Gary’s family’s Alzheimer’s gene, Gary made a discovery of his own. That August, his younger brother and his sister-in-law were visiting, and it was clear that his brother had Alzheimer’s. He would become confused by the simplest things. That first morning, he tried to open a latched door, gave up, then tried to open a window, thinking it was a door. Gary was desolate seeing his brother’s condition and could not help thinking that he could be next.