The same generation that gave us granola, the running boom and Viagra is now focusing its fitness concerns on a new region - the brain.
As the first of the baby boomers celebrate their 60th birthdays, many are starting to worry about preserving not only their physical health but their mental agility, too.
"We're seeing a sort of memory-fitness movement," says Dr. Gary Small, director of the University of California, Los Angeles Center on Aging and author of The Longevity Bible: 8 Essential Strategies for Keeping Your Mind Sharp and Your Body Young, which hit bookstores last week. "The fact is that we're living longer, but what's the good of making it to 110 if you don't have your mental faculties?"
Like most researchers, Small advocates a use-it-or-lose-it approach to cognitive fitness. Though it doesn't guarantee you will never fall victim to Alzheimer's disease - just as a healthful diet and exercise don't guarantee you will never have a heart attack - it may delay the onset of the disease or at least make a normal but aging brain more efficient.
In fact, a recent study by Small showed that after just two weeks on a program of healthful food, daily walks, relaxation techniques and mental exercises, participants had a significant improvement in verbal fluency - retrieving the right word from their memory banks quickly.
Such findings, coupled with an increase in U.S. life expectancy from age 47 to 77 in the past century, have given rise to a plethora of self-help books on bolstering brain power, two recent Nintendo video games aimed at baby boomers that purport to "train your brain in minutes a day," and even "Neurobics" classes in retirement communities.
Like other parts of the body, the brain changes with age. Synapses fire more slowly, some cells die off and the overall mass of the organ shrinks.
But studies of twins show that not all of the change is genetically predetermined, nor is a resulting loss of mental agility necessarily inevitable.
"There are many factors involved in developing memory problems, just as there are for heart disease," says Dr. Zaldy S. Tan, director of the Memory Clinic at Beth Israel Deaconess Medical Center in Boston and author of Age-Proof Your Mind: Detect, Delay, and Prevent Memory Loss - Before It's Too Late. "The important thing to remember is that there are things you can do to tip the scales in your favor."
Recent studies on brain function show that older brains can be trained to perform certain tasks as quickly as younger brains, that physical exercise is closely linked with mental sharpness, and that older adults who kept working or stayed active after retirement did significantly better on IQ tests than those who didn't.
In fact, researchers have found that seniors are able to reverse the decline in mental abilities typically associated with aging by doing memory, reasoning and mental-processing exercises. Further, studies with mice have shown that physical exercise led to structural changes in the brain, prompting the growth of new neurons and the connections between them.
Those findings may explain why people who stay active mentally - as well as those who have higher levels of education - have lower rates of developing Alzheimer's disease, which afflicts half of Americans older than 85.
Skeptics, though, point out there is no evidence of a direct link.
"It could also be that a third factor, such as intelligence, leads to greater levels of education and independently to lower risk of dementia," writes Margaret Gatz, a psychology professor at the University of Southern California. Scottish researchers, for instance, found those with higher IQ scores at age 11 went on to have lower rates of dementia decades later.
Gatz is not opposed to mental exercise - if undertaken to improve specific daily functioning or simply for pleasure - but she worries that the use-it-or-lose-it mantra will lead to false hope and, worse, to Alzheimer's victims being blamed for their disease.
Instead, Gatz agrees with researchers who emphasize the other components of a healthy brain - sound nutrition, sufficient sleep, stress management, treatment of depression and anxiety, physical exercise and avoiding head trauma by, for instance, wearing a helmet while bicycling.
"I do work crossword puzzles," she adds in an e-mail, "because I find it relaxing and because it is an activity that my spouse and I do together."
But if the relationship between intellectual stagnation and Alzheimer's is open to interpretation, there are still plenty of people who figure it can't hurt to beef up their mental exercise, just to be on the safe side.
Tan is one of them.
"People in their 40s should start thinking about this," he says. "As with cancer and heart disease, the earlier you start taking preventive steps, the better. Since they've found that people with higher levels of education are at lower risks of developing problems, you could argue that, even in your teens or 20s, you could start building brain reserves - in addition to getting a good education."
Dr. Ross Katzman, an Orlando, Fla., dentist, would tend to agree. Each day, Katzman, 51, works the Sudoku puzzle published in the newspaper - not that he doesn't get plenty of mental stimulation on the job.
"I don't know that it's going to help keep things sharp. I really just do it for pleasure," he says. "But it doesn't hurt, and maybe it'll be a warning sign when I can no longer solve the puzzle."
Kate Santich write for the Orlando Sentinel.