The audience wasn't happy. Its members — private citizens, health-care professionals and advocates for the elderly — had gathered to hear a report on how to prevent Alzheimer's; instead, they were told that, in fact, nothing has been proved to keep the disease at bay.
"We're not trying to take anyone's hope away," said report co-author Carl C. Bell, a professor of psychiatry and public health at the University of Illinois, Chicago, who noted the dejection in the air that day. "But we have to go with the hard science."
The bleak assessment was issued by a National Institutes of Health task force at an April meeting in Bethesda, Md. It was a State of the Science summary of more than 250 studies on potential ways to lower risk of the disease — and it was entirely accurate: None of the data had been strong enough for experts to definitively say "Do this" or "Don't do that."
But that's not to say the prevention picture is without hope. Several healthy and inexpensive strategies are clearly worth trying, say neurologists and Alzheimer's researchers.
"There is an emerging body of evidence on what you can do to reduce your risk," said Debra Cherry, executive vice president of the California Southland Chapter of the Alzheimer's Association. "It's not at the levels of research from randomized, controlled trials, but it suggests things are moving in the right direction. We are learning how to reduce risk."
The strategies with the most support are regular physical activity, a Mediterranean diet and high levels of cognitive engagement.
There would appear to be little to lose. Among people 55 and older, 1 in 8 will develop Alzheimer's disease and 1 in 6 will develop some type of dementia.
Here's a look at some of the steps everyone can take:
Perhaps the best way to potentially cut the chance of developing Alzheimer's is to exercise — regularly and with at least moderate intensity.
A large, long-term study presented earlier this month at the Alzheimer's Association International Conference on Alzheimer's Disease meeting in Honolulu found that people who perform moderate to heavy levels of exercise have a 40 percent lower risk of developing any type of dementia compared with people reporting the lowest level of exercise.
The study doesn't prove cause and effect, but it is noteworthy because of its size and the source of its data. The 1,200 participants, who had an average age of 76, were part of the long-running Framingham Study on cardiovascular health; their physical activity levels were recorded for at least a decade, along with the incidence of dementia.
Biological studies also support the idea that activity is good for the brain. In studies at the University of California-Irvine, Carl Cotman has shown that exercise increases levels of a substance called brain-derived neurotrophic factor, which enhances brain function and promotes the survival of neurons.
"There is a lot of data from epidemiology studies and animal studies supporting physical activity," said Laurie Ryan, program director for Alzheimer's disease clinical trials at the National Institute on Aging. "Exercise really is promising."
But just any movement might not do. The data, she points out, suggest that moderate to heavier exercise is more beneficial than mild physical activity, such as stretching.
Numerous population-based studies suggest that people who eat a diet high in fruits, vegetables, nuts, red wine and omega-3 fatty acids — and low in saturated fats — have a reduced risk of dementia of any type.
"Dietary factors are important," Ryan said. "The Mediterranean diet seems more beneficial than the standard Western diet."
Omega-3 fatty acids, in particular, have been linked to a reduced risk of developing Alzheimer's. A 2005 Cochrane Review article stressed that research on omega-3s should be a priority. Because it can be hard to get enough of these nutrients from the diet — they're found most plentifully in salmon and sardines — some experts suggest taking a supplement of 1 or 2 grams a day.
Other dietary elements have also emerged as especially promising; among them are alcohol and tea.
Several studies have linked light to moderate alcohol intake with a reduced risk of dementia. One of the most solid pieces of research, published in the Lancet in 2002, followed more than 5,000 healthy people ages 55 and older for at least six years. That work, called the Rotterdam study, found that light-to-moderate drinkers had a 42 percent lower risk of dementia as compared with non-drinkers.
As for tea, a study presented at the recent International Conference on Alzheimer's Disease adds to the growing body of research suggesting its benefits. It found that, over time, tea drinkers have rates of cognitive decline 17 percent to 37 percent lower than non-tea drinkers.
Some studies suggest that living with someone is protective — and there is strong evidence that the loss of a spouse leads to decline. Further, staying mentally engaged also seems to be beneficial.
One of the best-known studies on this second connection is the work by David Bennett, a professor of neurological sciences at Rush University Medical Center in Chicago. His research, called the Religious Orders Study, found that people who spent the most time engaged in mentally stimulating activities — such as reading, playing cards or doing puzzles, going to the museum — had a 47 percent reduced risk of developing dementia compared with those with the lowest rates of cognitive activity.
When to start
The timing of preventive strategies may prove crucial, with the notion of "the earlier, the better" seeming to hold true. It may be wise to adopt a healthful diet and exercise regimen as soon as possible. "These lifestyle factors may have to occur early in life," Ryan said.
That doesn't mean that older people can't decrease their risk. Research strongly implies that diseases that develop later — such as heart disease, diabetes, hypertension and obesity — raise the possibility of dementia. Researchers are now exploring whether medications used to treat these conditions may also reduce Alzheimer's disease risk.