Staying healthy, exercising , eating a diet rich in omega-3 fatty acids and other healthful foods, and keeping your mind engaged have all been suggested as ways to stave off cognitive decline and the brain disorder known as Alzheimer's, marked by a loss of memory and other cognitive ability.
But the independent panel, convened by the National Institutes of Health, concludes that there is insufficient evidence that any of these measures prevent Alzheimer's.
The conclusion, although probably disappointing to many, may not be as discouraging as it sounds, says Carl C. Bell, MD, a panel member who is also director of the Institute for Juvenile Research, professor of psychiatry and public health, University of Illinois at Chicago, and president and CEO of the Community Mental Health Council, Chicago.
''We had to follow the science," he says, explaining that the panel applied rigorous scientific standards to the numerous studies reviewed to determine if any measures might be proven to prevent Alzheimer's disease or cognitive decline, which precedes it.
They found the evidence lacking, Bell tells WebMD. "There is no hard science right now."
But that doesn't mean there won't be, someday, says Martha Daviglus, MD, PhD, MPH, chair of the panel and professor of preventive medicine and medicine at Northwestern University's Feinberg School of Medicine. "Right now research is being conducted in promising areas, such as omega-3, physical activity, and cognitive engagement," she tells WebMD.
About 5.3 million Americans have Alzheimer's, the majority of them late-onset disease that becomes apparent after age 65.
The panel's report, as well as the background information supplied them, is published in t he Annals ofInternal Medicine.
Preventing Alzheimer's: The Panel's Work
The NIH-convened panel, made up of 15 independent experts, spent three days in April looking at data gathered by a team of experts from Duke University Medical Center and the Durham Veterans Administration Medical Center.
Brenda L. Plassman, PhD, a Duke researcher, and her colleagues gave the panel the results of a systematic review that included 127 observational studies each looking at 300 or more participants, 22 randomized, controlled studies with at least 50 participants followed for at least a year, and 16 systematic reviews of various preventive measures.
The study topics covered a broad range, from nutrition to medical factors and medication , social, economic and behavioral factors, exposures to toxin, and genetics.
Preventing Alzheimer's Disease: Panel Conclusions
Overall, the panel says: "Currently, firm conclusions cannot be drawn about the association of any modifiable risk factor with cognitive decline or Alzheimer's disease."
The panel also says the evidence is ''insufficient'' to support the use of pharmaceutical agents or dietary supplements to prevent cognitive decline or Alzheimer's disease.
Yet they suggest the ongoing research on omega-3 fatty acids, physical activity, and cognitive engagement -- keeping mental faculties sharp -- "may provide new insights into the prevention or delay of cognitive decline or Alzheimer's disease."
The conclusion of no definitive link even applies to those with the ApoE (apolipoprotein E) gene, associated with late-onset Alzheimer's. "Not everyone who has ApoE will get it," Daviglus says.
The panel members called for more research. "One thing the report has shown us,'' says Bell, emphasizing that this is his opinion, is, ''we probably need to look at intervention [in research studies] at an earlier age."
Many studies include participants who are older when the research begins, he says and the cognitive decline may have already begun.
Preventing Alzheimer's Disease: Other Opinions
As discouraging as the report conclusions may seem, there is reason for hope, says Greg Cole, PhD, associate director of the University of California Los Angeles Alzheimer's Center and director of dementia research at Cedars-Sinai Medical Center, Los Angeles. Cole has been an expert panel member for Martek Biosciences Corporation, which makes omega-3 products. He reviewed the report for WebMD.
"I think the panel is duly cautious," he says, noting that they followed the edict to review rigorously the science and accept only conclusive evidence.
''But I think they are less optimistic than what would be warranted," he says.
Likewise, Maria Carrillo, PhD, senior director of medical and scientific relations for the Alzheimer's Association, says the conclusions should not discourage people. "Our first reaction is that we understand there are no definitive answers [for preventing Alzheimer's disease] and we've been saying that."
But the panel, she says, "actually laid out a fantastic research agenda for getting those answers."
Meanwhile, she says, people should continue to follow good healthy habits -- especially those designed to minimize heart disease. "There is evidence that reducing those risks can improve your brain health," she says.
Daviglus agrees. ''We should advise the public to continue to have a healthy lifestyle and to keep cardiovascular disease risk factors controlled," she says.
By Kathleen Doheny
Reviewed by Laura Martin
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