"The normal aging of the brain is very different from what happens in AD. The old thinking was that the normal cognitive changes in aging were the result of cell loss throughout the brain," said Dr. Albert, director of the division of cognitive neuroscience, department of neurology, The Johns Hopkins University School of Medicine and chair of the Alzheimer's Association Medical and Scientific Advisory Committee. "We now know that while there is some cell loss in the aging brain, cell loss in the areas responsible for memory is normally very limited." Dr. Albert spoke today at an American Medical Association media briefing on Alzheimer's disease in New York City.
Changes in brain chemistry that result in changes in the way the neurons communicate are more likely to be responsible for the memory problems associated with normal aging, according to Dr. Albert. "The memory loss and other cognitive changes in AD, however, are the result of profound neuronal loss in the parts of the brain critical for memory. These areas are the first affected by AD, although the destruction of nerve cells continues to progress throughout all areas of the brain."
"There is enormous interest in finding out what we can do to keep our brains healthy. Three NIH Institutes (the National Institute on Aging, National Institute of Mental Health and the National Institute of Neurological Diseases and Stroke) are putting together a collaborative effort to bring together what we already know and to find cost-effective ways of extending our knowledge," said Dr. Albert.
Researchers will analyze data from past studies and look at ongoing studies to see if there are ways to get a lot of new cognitive data without the expense of mounting gigantic new studies. For example, by adding a cognitive arm to ongoing prospective observational studies in younger individuals, such as those related to risks for heart disease, a great deal might be learned with modest expenditures of funds.
"We are already learning that there may be ways of maintaining general brain health that can be safely recommended to everyone and could have a real impact on helping people maintain the brain's repair mechanisms, resilience and responsiveness," said Dr. Albert.
Dr. Albert emphasized that while nothing had been proven so far, there are a number of indications that reducing oxidative stress, increased physical and mental activity and reducing stress may all improve general brain health. Whether they have an impact on the formation of plaques and tangles, the hallmarks of AD, is still unknown. "Vitamin E, an anti-oxidant, has already been tested and shown to somewhat reduce AD symptoms. Increased mental activity may achieve a protective effect by increasing the connections between nerve cells," said Dr. Albert. "We know that vitamin E is relatively safe and physicians can feel comfortable recommending it. And, of course, there just doesn't seem to be any downside to increased mental and physical activity."
There are really two separate issues in preventing or delaying the likelihood of developing Alzheimer's disease, explained Dr. Albert. "There is an enormous interest in finding ways to keep our brains healthy as we age. But, we can't tolerate side effects in primary preventive measures that we might offer to a healthy population. At the same time, when we do have effective treatments, they are not likely to be benign. We are only willing to give people medications that may have serious side effects for a very good reason. We will, therefore, need to learn to identify who is truly at risk."
There are a number of different ways that researchers are approaching the problem of early identification, explained Dr. Albert. One strategy is to identify people with mild cognitive impairment, some of whom have early changes in the brain caused by the plaques and tangles. Other investigators are using PET scans and MRI to look for changes in the brain, for example, blood flow or brain shrinkage. There are also researchers who are attempting to image the plaques themselves.
"The tremendous effort going into research on Alzheimer's disease reflects the high interest of finding a way to prevent Alzheimer's," said Dr. Albert. "We will be seeing that pay off in a lot of information that will help us find effective treatment."