The first update in nearly 30 years to U.S. guidelines for the diagnosis of Alzheimer's disease expands the definition to include patients with earlier stage symptoms and recognizes the condition as being on a continuum rather than just end-stage dementia. Such methods measure what are called biomarkers, physiological indicators that someone is likely to develop dementia eventually, just as cholesterol and blood pressure are biomarkers of impending heart disease. Though several biomarkers related to Alzheimer's have been identified already, they aren't ready for clinical usage yet owing to a lack of standardization about how the tests are performed and what should be considered the cutoff point for a normal result, said Marilyn Albert, director of the Johns Hopkins Alzheimer's Disease Research Center. People diagnosed with Alzheimer's tend to be 65 and older, but evidence suggests that signs of the memory-robbing disease, like amyloid protein plaques and nerve cell death, may start in the brain five to 10 years before they can currently be detected. They are intended to encourage more research so that drugs can be developed to attack early brain changes and to identify people who might benefit from such drugs when they become available. The goal, said William Thies, chief medical and scientific officer for the Alzheimer’s Association, is “extending the range of our ability to investigate this disease and eventually find the treatment that is going to be so necessary to avoid the epidemic of Alzheimer’s disease that we see facing us over the next 40 years.” 
 
 In the short term, the biggest impact is likely to be seen with people who fall into the middle phase, those with mild cognitive impairment linked to Alzheimer’s. Experts say there are at least as many people experiencing this phase as the 5.4 million people estimated to have Alzheimer’s dementia.
– Alzheimer's disease is being redefined for the first time in 27 years, with new medical guidelines reflecting the fact that the disease is a "continuum." Growing evidence shows that Alzheimer's starts affecting the brain years before dementia symptoms present themselves, and the new guidelines reflect that by dividing the disease into three stages: end-stage dementia, a middle phase involving mild problems, and a symptomless beginning stage where the brain has already begun to change. "I think we’re going to start to identify it earlier and earlier," says one expert. The new guidelines are concerned with measuring biomarkers, or indicators that a person will likely develop dementia, in clinical trial patients, the New York Times reports. The Wall Street Journal notes that earlier diagnosis of the disease will also allow earlier intervention, and could someday allow patients to take Alzheimer's-slowing drugs earlier.