Retired geometry teacher Kay Sokoloff has always loved puzzles, crosswords, and mind benders, so she was pleasantly surprised to learn that this particular addiction is good for her health. Sokoloff, of Ocean Isle Beach, North Carolina, turned 60 this year, and her mind is as sharp as the proverbial tack. It's little wonder her screen name is atop the leader board at the brainteaser site of www.eons.com, an Internet community for folks over 50.

Building up cognitive reserves was not her intent, but research suggests the time Sokoloff spends on Sudoku, mah-jongg and Zuma may be doing Just that: creating a line of defense in the battle to ward off Alzheimer's disease and other forms of dementia.

A preventive? No, but a "retardant," is how Dr. Thomas Perls describes it. Perls is associate professor of medicine and geriatrics at Boston University Medical School and consultant to eons.com. He's also the founder and director of the New England Centenarian Study, the largest study of 100-year-olds ever conducted.

Perls likens the connections between brain cells to telephone lines connecting cities in the days before cellular. Snip the lines until none remain and communication will stop between cities. So it is with growing old. As our brain's connecting wires deteriorate, our memory and mental functions follow suit. But engaging in mental exercises may help us be able to build new lines and delay the day of reckoning. "These cognitive exercises may translate into the production of new connections between brain cells," Perls said.

Because scientists don't know exactly what causes Alzheimer's, there are no guarantees that building new connectors will dissuade the dread disease that robs the aging of their memories and personalities. But there's ample evidence to suggest that mental and physical exercise can improve the health of our cerebrums. In June, the medical Journal Neurology published a longitudinal study of more than 1,200 older people which found those who kept mentally active were 2.6 times less likely to develop dementia and Alzheimer's than those who did not. "This study provides the strongest evidence to date there really is a causal relationship between late-life cognitive activity and risk of memory loss and dementia," said study author Robert S. Wilson, a neuropsychologist at the Rush Alzheimer's Disease Center.

To put it another way, people can control at least one risk factor for the disease as they age. For baby boomers, that's reason enough to start doing Jigsaw puzzles, playing chess, or taking up the piano. Log on to eons.com and you'll find boomers doing Just that, playing games with names like Scrabble Blast, Rocket Mania, and Bounce Out. The activities, selected in consultation with Dr. Perls, cover five critical cognitive areas: visual-spatial skills, motor function, executive function, language, and memory. "The baby boomers are a key population," Perls said. "The oldest ones are in their early 60s, and they're a little interested in what they can do to keep this stuff at bay."

A fear of losing our marbles as we age is, sad to say, well grounded in statistics. In the United States, an estimated 5.1 million people suffer from Alzheimer's. According to the Alzheimer's Association, that includes one out of five people between 75 and 84 and 42 percent of those over 85. Worldwide, more than 26 million people have the disease, a number projected to quadruple by 2050.

The extent of the coming epidemic was made clear in June during the association's International Conference on Prevention of Dementia in Washington, D.C. For four days, professionals from the medical and public policy fields discussed the latest in detection, treatment, and prevention research. The news coming out of the conference was at the same time depressing and hopeful.

This is the healthcare crisis of the 21st century, said William Thies, vice president of medical and scientific relations with the Alzheimer's Association. In 2011, baby boomers start turning 65, the age of greatest risk for Alzheimer's. Barring discovery of a cure or an amazing new treatment regimen, the effects on society will be staggering. Some examples from the Alzheimer's Association: It costs $148 billion a year to care for Alzheimer's patients in this country, about $91 billion of which comes from Medicare. The cost of one year of in-home care is $200,000. According to a Metlife survey, a year of nursing home care can exceed $75,000.

Now for the hopeful news. A mad search is under way for cures and preventive measures. The National Institutes of Health is supporting 22 studies related to Alzheimer's. Most of the attention to date has been on developing drugs to prevent, treat, or slow down progression of the disease. Some of these have made it to the third stage of clinical trials, which means early test results were promising. (The four Alzheimer's drugs now on the market deal only with symptom management. and none alters the course of the disease.)

"We're very pleased to see several compounds in Phase III clinical trials now for Alzheimer's disease that represent a variety of treatment strategies," Sam Gandy, chair of the Alzheimer's Association's Medical and Scientific Advisory Council, told the international conference. "The odds are quite good that we'll have more effective new treatments for Alzheimer's in the near future."

Though a cure still seems wishful thinking, delaying onset of the disease is a reasonable goal, and one that could be attained through drug treatments or societal efforts to improve brain health. Consider: Delaying onset in patients by Just a year would reduce the number of cases in the United States by 12 million as of 2050. That would save $1.2 trillion in healthcare and productivity costs, according to a study funded by Accelerate Cure/Treatments for Alzheimer's Disease, a coalition of national organizations representing patients, providers and caregivers.

One strategy is to give the brain the same kind of attention that antismoking and obesity campaigns have drawn to the body in recent years. That process began at the international conference when officials issued a report titled. "The Healthy Brain Initiative: A National Public Health Road Map to Maintaining Cognitive Health." The Road Map described its long-term goal as "lofty but achievable…: To maintain or improve the cognitive performance of all adults."

Research shows that brain health Is closely linked to the health of our hearts and blood vessels. "All the things that we know are bad for your heart turn out to be bad for your brain," Marilyn S. Albert of the Johns Hopkins University Alzheimer's Disease Research Center says In the Road Map. Thus every time we go to the gym, we not only reduce the risk of cardiovascular illness, but we strengthen the brain against cognitive decline. Likewise, managing weight, blood pressure, and cholesterol benefits body and mind. Even flossing our teeth is important because it reduces inflammation, which is an Alzheimer's risk factor.

The Road Map was authored by the Centers for Disease Control and Prevention and the Alzheimer's Association, which said in releasing the report, "While there is yet no conclusive evidence that brain-healthy behavior can prevent or alter the course of Alzheimer's, it has been suggested that maintaining or improving the public's cognitive health could have enormous social and economic value."

If that statement sounds overly cautious, it reflects controversy within the medical community over whether cognitive inactivity is a risk factor or consequence of Alzheimer's. Wilson, author of the Rush Medical Center study, said it's clear that keeping mentally active--reading a newspaper, attending a play--reduces risk.

After studying centenarians, Dr. Perls is convinced mental engagement can improve quality of life. It's a myth that the older we get, the unhealthier we become, Perls said. The older we get, the healthier we've been.

In the same way that muscles and bones benefit from strength training in the gym. our brains benefit from mental activity. The key, he stressed, is to select activities that are novel and complex, "things that are cognitively really hard." Sudoku, which used to give him fits, is a good example. The game is in essence a logic puzzle, requiring the player to fill numbers into a grid so that each column, row and three-by-three section contains the numbers I to 9 only once. It's tricky, especially if you haven't worked with numbers since high school.

"I persisted and now I'm not so bad at it," said Perls, who notes that his school-age daughter had little trouble when she first tackled the exercise. The younger brain is indeed more agile. Once you master a game. he advises, it's time to move on to something else, in the same way a weight-training athlete would add repetitions or rotate muscle groups.

Crossword puzzles, Jeopardy, learning a new musical instrument, all fit the bill. According to Perls, "the conduct of those activities seems to delay the onset of memory loss," a precursor of Alzheimer's.

Humans, one of the nation's large health insurers, is so encouraged by the possibilities that it is offering free to its Medicare Advantage members computer software designed to boost memory and thinking skills in older adults. The Brain Fitness Program, made by Posit Science Corp., offers a series of computer based exercises at a cost to individuals of $395.

The scientific basis for the program is a theory known as plasticity, or the brain's ability to develop and change. The old assumption was that plasticity ends at some point in the aging process, and that the wear and tear on our brain ceils becomes inevitable and irreversible. The current view is that brains remain plastic for life and that new "telephone lines" can continue to be built indefinitely. According to Posit Science's researchers, "a large and growing body of animal studies has shown that an enriched environment designed to be cognitively stimulating promotes positive plastic changes in the brain and can reverse the negative physical, sensory, and cognitive aspects of aging."

Kay Sokoloff, whose parents died at a relatively young age, said that's extremely good news and is further reason to keep feeding her brainteaser addiction. "That was never my purpose, It's just a nice benefit," she says, adding, "I'm very fearful of not aging well."

Perls has met enough centenarians to know that a lifetime of fitness and mental stimulation will pay off in healthier aging. He's sold on the concept of retirement communities on college campuses so older folks can stay intellectually active and serve as mentors to the next generation.

So which is better for the brain? Physical or mental exercise? Doing sedentary crosswords or sweat-producing aerobics? What should baby boomers do if they have limited time to engage in brain fitness activities?

The only safe answer is: All of the above. Stay fit and trim, play brain games, and floss your teeth, Perls said. "Walk on a treadmill while you're doing Sudoko. That would be the best thing."