No easy answers for aging’s ‘defining’ illness
August 7th 2011 09:19
Virginia Stone is worried: Alzheimer's disease seems to run in her family. Her 80-year-old mother, Kazue Storey, was diagnosed seven years ago, and Storey's mother died of the disease in the 1970s.
So Stone, 53, watches her diet, and she works out at Zumba class several times a week. She's cut out almost all caffeine, except for one Diet Pepsi every week. She works puzzles like Sudoku and crosswords.
"If you take care of all these things, you can put off dementia longer," said Stone, marketing director for Carmichael Oaks Senior Living.
Her approach certainly sounds like common sense. In fact, many Alzheimer's specialists tell their patients that what is good for the heart – a healthy weight, daily exercise, no smoking, lots of fruits and vegetables, a network of social connections – is also good for the brain.
But is that true? Will a healthy lifestyle help prevent Alzheimer's disease, or at least delay its onset?
As the number of Alzheimer's cases in the United States continues to climb, such questions have taken on an urgent feel. The Alzheimer's diagnosis is now shared by 5.4 million Americans, and that number is expected to rise to 16 million by mid-century.
The Alzheimer's Association calls the illness "the defining disease of baby boomers" – many of whom, like Stone, are already dealing with it in their parents' lives.
For them, it's crucial to know whether lifestyle changes will make a difference. But the answer, like so much related to Alzheimer's, is hard to pin down definitively.
"Alzheimer's is a complicated condition," said Bill Fisher, Alzheimer's Association of Northern California chief executive officer. "The answers are also going to be complex."
Strictly speaking, experts say, the only known risk factor for Alzheimer's is old age. Marked by the death of brain tissue and the resulting erosion of memory and ability to function, the disease is already the nation's sixth-leading cause of death and thought to be responsible for 80 percent of dementia cases.
There is no cure, although one medication, Aricept, has been found to delay symptoms in some patients for a year or two.
Unfortunately, as Fisher points out, research on Alzheimer's – unlike research on other major killers, such as cancer and heart disease – remains in its infancy.
In large part, that's because for most of the 20th century, doctors thought Alzheimer's only caused those rare cases of dementia occurring before age 65, while they diagnosed dementia in the elderly as a different disease, one that was thought to be a normal, if not inevitable, part of growing old.
Once researchers concluded in the 1980s that the pathologies of early and old age dementias were the same, the science could make progress.
Study suggests risk factors
Today, scientists know that Alzheimer's begins its steady march of killing brain cells 10 years or longer before forgetfulness, confusion and other early symptoms appear. By the time memory problems start, the disease is already consuming the brain.
Prevention, or even simply finding ways to keep symptoms at bay for another decade into old age, would be a major breakthrough for older adults concerned that dementia might be in their future.
And there are tantalizing hints that lifestyle changes really might help.
A new UC San Francisco study – using a sophisticated mathematical model to analyze many years' worth of observational data about the influence of lifestyle on Alzheimer's – suggests that about half the world's known cases of the disease could be attributable to seven modifiable risk factors.
Lack of exercise could cause 21 percent of Alzheimer's in America, and high blood pressure could cause 8 percent, the study theorizes, while low educational attainment and midlife obesity might each cause 7 percent. Diabetes could account for 3 percent.
"The message is, we can't promise you that if you change your lifestyle you won't develop dementia, but based on the data we have available now, we think it might make a difference," said Deborah Barnes, the San Francisco Veterans Affairs Medical Center mental health researcher who co-authored the study.
"And for society, it could make a difference in the number of cases that develop over time."
Or maybe not.
As an independent panel appointed by the National Institutes of Health to assess a broad range of research on the disease found last year, the problem with connecting lifestyle risks and Alzheimer's is this: Many studies find correlation, but none definitively proves cause.
Why? Because none has involved the analytical rigor of randomized, controlled trials, the gold standard of modern science.
"Our response to that is, you can't," said Charles DeCarli, director of the UC Davis Alzheimer's Disease Center. "You can't tell half your group, 'Don't treat your diabetes.' You can't tell half your group, 'Don't treat your hypertension.'
"NIH was correct that there are no controlled studies showing the benefit of lifestyle changes. But they missed the spirit of the science."
Scans find brain changes
DeCarli's own new research, published in this month's Neurology medical journal, followed people in midlife who had diabetes or weight problems or were smokers.
Brain scans taken at 50, then again at 60, found significant changes in most participants' brain structure – notably including the structure of the hippocampus, the brain's memory center, one of the first regions that Alzheimer's disease damages.
Again, it's a clue that people's behaviors earlier in life could put them at increased risk of dementia as they grow older.
"We have accumulating evidence saying that lifestyle modifications may help," said Dr. Laurie Ryan, program director for Alzheimer's disease clinical trials at the National Institute on Aging.
Among those trials are research on whether exercise, cognitive training and certain supplements, such as fish oil, can help stave off Alzheimer's.
"There's accumulating data that diet and being physically active and staying socially engaged promote healthy brain aging," she said. "But we can't prescribe those yet.
"Can we say, 'Do these things, and you won't get Alzheimer's?' No. But this is something people can take control of. They'll age better. It will help, but it's not a guarantee."
Researchers know that many people live energetic, involved lives and eat right but still get dementia. But for many other people, said Ryan, it's possible that healthy habits will help keep their brain pathways nimble enough that they never exhibit cognitive decline, even if they have other evidence of Alzheimer's pathology.
For example, researchers think higher levels of education protect against Alzheimer's, because the brain fairly early in life learns to make new neural pathways, improving thinking and memory abilities – what experts call "cognitive reserve."
Besides, said Fisher: "Lifestyle changes are something you can do that doesn't require a pharmaceutical company to develop something that doesn't exist yet."
In other words, exercising, eating better, doing crossword puzzles and playing bridge with old friends can't hurt. And they just might help.
Hope is all Virginia Stone wants.
Her mother, who lives in Palo Alto, began showing signs of memory loss almost a decade ago, Stone says. And the slow, sad progression began.
Stone changed career fields – from retail sales to senior living – because she wanted to understand Alzheimer's and learn how to better support her father, Jack Storey, 86, who takes care of Kazue.
"Even if you're not worried about Alzheimer's, taking care of your body is good for you," she said.
"If I can put off Alzheimer's for a few years, that's good. And if I can put off the inevitable long enough, maybe I'll never get it."
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