El Alzheimer empieza antes de la demencia

Les compartimos este artículo publicado por el New York Times

Guidelines Allow Earlier Definition of Alzheimer’s

By PAM BELLUCK

For the first time in 27 years, the definition of Alzheimer’s disease is being recast in new medical guidelines that reflect fast-mounting evidence that it begins ravaging the brain years before the symptoms of dementia.

The guidelines, to be issued Tuesday by the National Institute on Aging and the Alzheimer’s Association, divide the disease into three stages: a phase when dementia has developed, a middle phase in which mild problems emerge but daily functions can still be performed, and the most recently discovered phase, in which no symptoms are evident but changes are brewing in the brain.

“We’re redefining Alzheimer’s disease and looking at this in a different way than had ever been done,” said Creighton Phelps, director of the National Institute on Aging’s Alzheimer’s Disease Centers Program. “I think we’re going to start to identify it earlier and earlier.”

The drive to diagnose Alzheimer’s before it has progressed into profound dementia is also reflected in a bill introduced in Congress this month, which would create specific Medicare cost codes for Alzheimer’s diagnosis, including steps involving discussions between the patient’s doctor and caregivers, a recognition that keeping family members well-informed can result in better planning and care.

“Early diagnosis is really the key to this,” said Representative Edward J. Markey, Democrat of Massachusetts and a sponsor of the bill. “Oftentimes family members notice the symptoms in their loved ones, but it’s only years later that they get diagnosed or understand what resources are available.”

The most striking addition to the guidelines concerns methods that assess brain changes involved in Alzheimer’s, including brain scans and tests of cerebral spinal fluid. 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.

For now, the guidelines specify that Alzheimer’s biomarkers — including abnormal levels of the proteins amyloid and tau, and shrinkage of certain brain areas — should not yet be put into widespread use, but used only with patients enrolled in clinical trials.

That is because scientists cannot yet standardize the results of the tests, or know “what measure is truly abnormal and what measure is not,” said Marilyn Albert, director of the Johns Hopkins Alzheimer’s Disease Research Center, and a leader of one working group that developed the new guidelines.

As many as a third of people with amyloid plaques in their brains, for example, have not developed Alzheimer’s symptoms by the time they die. The guidelines also urge caution because there is currently no drug known to halt or significantly delay the onset of symptoms, so people told they are likely to get Alzheimer’s have no effective medication to take.

“We don’t have enough information about what to tell people,” said Dr. Steven DeKosky, dean of the University of Virginia medical school, who participated in one of the working groups. “Until you can tell a clinician, ‘If you do this test you have X amount of reliability and to do that will make a difference in the life of your patient’ — until then, it remains in the lab.”

But the guidelines reflect a sense in the medical community that the moment when science will have more specific knowledge about biomarkers is not that far off. 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. And they expect others to now ask their doctors if they are showing signs of mild impairment, which include experiencing some difficulty or inefficiency with memory, attention or other mental faculties, while still being able to function independently.

Dr. Albert said that if patients with symptoms of mild cognitive impairment wanted to “increase the certainty” of the diagnosis by getting a brain scan or spinal fluid test, they should obtain such tests in a research trial so they have a better chance of getting accurate results.

The guidelines also clarify diagnosis criteria for people with dementia symptoms, distinguishing Alzheimer’s from other dementias, including vascular, fronto-temporal and Lewy body. And they note that the earliest symptom of Alzheimer’s dementia is not always memory loss, but could be mood changes or problems with language, spatial perception or reasoning.

Dr. Pierre Tariot, director of the Banner Alzheimer’s Institute in Phoenix, who was not involved in drafting the guidelines, called them “a step in the right direction” that he hoped would not be “misconstrued” as a sign that biomarker tests are further along than they are. He added, “The notion that Alzheimer’s disease is a continuum that has an extensive pre-symptomatic phase is a very important message to get out.”

Dr. Phelps said it would hardly be the last word from the medical community on Alzheimer’s.

“We’re not drawing a line and saying this is it,” Dr. Phelps said. “What we’re saying is this is the best of our knowledge and we’re not going to wait 27 years to revisit these again.”

Link al artículo: http://nyti.ms/h51nZW

Categories Investigación, Lo Nuevo | Tags: | Posted on April 20, 2011

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