BETHESDA, MD—While the last 20 years have provided important insights into the nature and pathology of Alzheimer’s disease (AD) and cognitive decline, there is little evidence to support any of the various prevention methods currently being used, a panel of experts convened by NIH revealed last month. Mental stimulation, exercise, and a variety of dietary supplements have all been recommended and studied over the years as ways to forestall mental decline. However, after an extensive review of the literature, it was found that the value of any of them in delaying the onset or reducing the severity of decline in mental function has not been demonstrated.

Poor Understanding of Disease, Aging

“Alzheimer’s disease is a feared and heart-breaking disease,” said Dr Martha L Daviglus, chair of the NIH panel and professor of preventive medicine at Northwestern University, Chicago. “We wish we could tell people that taking a pill or doing a puzzle every day would prevent this terrible disease, but current evidence doesn’t support this.”

Daviglus and her colleagues recently gathered for a three-day conference where they heard testimony and reviewed the scientific literature collected over the last decade dealing with AD prevention. The result was less than heartening. The panel’s assessment revealed that the current gaps in understanding the root pathology of cognitive decline impede significant progress in forestalling it.

Included in those research gaps is an inconsistent definition of what constitutes AD and cognitive decline and how it differs from the natural history of the aging process, which is also poorly understood in general. While a number of genetic factors have been identified that convey increased risk for AD, aging still remains the strongest known risk factor for the disease.

The panel also determined that there is currently no evidence of even moderate scientific quality showing that any modifiable factor—dietary intake, use of medications, and social engagement—can be associated with reduced risk for AD. Panel members emphasized that research has not shown that these factors absolutely do not have any beneficial effect, but that the research is simply not there. Carefully designed studies may reveal that these modifiable factors enhance, detract, or have no effect on cognitive decline, they explained. But that research still needs to be done.

Filling in the Research Gaps

This does not mean that there is no hope for Alzheimer’s prevention. The panel noted that there are a number of ongoing studies that could show promise. Studies into antihypertensive medications, omega-3 fatty acid, physical activity, and cognitive engagement all have the potential to provide new insight into cognitive decline prevention.

“There are some trials of cognitive engagement—in training people in memory and reasoning and thinking, which have shown some small effect over a five year period in lessoning cognitive decline,” explained Arnold Potosky, PhD, professor of oncology at Georgetown University Medical Center, during a telebriefing following the conference.

One of the major conclusions of the panel was that large-scale population-based studies and randomly controlled trials are critically needed to investigate strategies to maintain cognitive function in individuals at risk for decline, to identify factors that may delay the onset of Alzheimer’s disease among individuals at risk, and to identify factors that may slow the progression of Alzheimer’s disease among individuals already diagnosed with the disease.

“Despite the conclusions that you’ve just heard, one of the most important things that doctors can do and people who are starting to recognize problems [can do], is to get engaged in the research community,” Potosky explained. “There’s a vital need for more research. And our conclusions were very heavy to examination of these diseases over the long term to understand their [pathologies].”

And while the panel’s findings will likely be seen as a negative, the panel members emphasized that anytime researchers can provide physicians with accurate information, it is positive for the patients. “We’re hoping our report is going to supply physicians with accurate information,” explained Dr Carl Bell, director of psychiatry at the Institute for Juvenile Research at the University of Illinois, Chicago. “[Physicians] like to give people information so they can make personal decisions on their own. [And that includes the fact that] there are no modifiable variables that are going to prevent cognitive decline, and people should know that so they make informed choices about how they spend their money.”

More information about this conference as well as video presentations can be found at http://consensus.nih.gov/2010/alzplanners.htm.

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