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For boomers and seniors worried about staying sharp, retirement communities and companies are pushing fitness for the mind -- exercises, games and classes that promise to stave off memory loss, improve your attention span and help you become more productive.

They're finding a receptive audience. The so-called brain fitness market -- which includes everything from handheld games and tests to group classes that are designed to keep seniors mentally sharp -- tripled from 2005 to 2009 to $295 million, according to the most recent data available from market research firm SharpBrains, which tracks brain fitness trends and technology. Retirement communities have also jumped on the bandwagon, with 60% offering some kind of mental acuity classes or programs nearly triple the percentage that did three years ago, says Colin Milner, president of the International Council on Active Aging. And a slew of software developers have entered the market with games, personalized "training programs," and other programs that promise to keep users on point -- at prices that range from a few dollars to several hundred of dollars.

The problem, experts say, is that all these exercises may not be worth the extra cash. "There's not strong evidence that tailor-made brain games are any better than just, say, reading or doing a crossword puzzle or doing something else to stimulate the brain," says Marc Agronin, director of mental health and clinical research at the Miami Jewish Health System and author of "How We Age."

Still, there's a good reason these products have found a niche. According to a 2010 survey by AARP, baby boomers are more concerned about "staying mentally sharp" than running out of money. A separate 2011 poll by the Associated Press finds boomers are significantly more afraid of a deteriorating mental state than they are of death: While 44% of boomers say that one of their top worries is losing their memory, just 18% say that death is on top of the list. As a result, the market for these kinds of products and services is projected to hit up to $8 billion by 2015, says Alvaro Fernandez, CEO of SharpBrains.

Some research suggests there's clear value in "brain training." And a 2010 study out of the University of California at Los Angeles found that brain fitness games improved seniors scores on a memory test by about 16%. And preliminary results from a Wake Forest University Baptist Medical Center study showed that doing as little as eight total hours of brain exercise -- in this case tasks in which you look for target words as distracting sounds are made -- can improve your ability to pay attention. "Brain fitness games can't perform miracles," says Fernandez. "But they can enhance memory and attention and help build cognitive reserves to delay memory loss."

There are also some very real limitations, says Agronin. For one, there is nothing they can do to prevent or treat Alzheimer's, one of the chief wreakers of havoc on older people's cognition, says Fernandez. And for healthy people, exercises can only do so much. Because they have what's called a "ceiling effect" -- they can only improve cognition to a point -- these products might not do much good for people who are already sharp, Agronin says. And like a physical fitness program, it's easy to fall out of shape: Seniors need to continue doing these games and program in order hold on to those improvements, he says.

For consumers interested in brain fitness, experts recommend starting small. Start with one of the free games offered at sites like cognitivefun.net and brainexperiment.org, says Christian Elliott, a cognitive researcher at MyBrainTest.org, which reviews cognitive tests. To get a sense of your baseline, New York-based Cognifit, a brain-training software and web development company, just re-launched its website which gives consumers a free brain fitness assessment -- it measures skills like contextual memory, response time and hand-eye coordination. It also provides users with a personalized set of free games that challenge things like your contextual and short-term memory, response time and hand-eye coordination (it also offers more advanced games for $4.99). Elliot says that while the site is "good," the game offerings are limited (currently CogniFit has just one paid game for memory, for example). Company CEO Nathanael Eisenberg says that at least one new offering will be rolling out in the coming weeks.

Another option, says Elliot, is Lumosity, which also offers an online assessment that tests memory, attention, speed, flexibility and problem solving, as well as personalized games. The costs: $14.95 a month or about $80 a year. "The games are good and the site is easy to use," Elliott says. The big downside: Since the company targets a broad audience of all ages, their offerings are pretty general, and thus there are limited specialized options for say, an older person who relatively significant cognitive decline, he says. A spokesperson for the company says that "this is accomplished without making any compromises by automatically adjusting the difficulty of each activity to the ability of the user." Finally, Posit Science, one of the oldest and most-established brain fitness companies, offers a software program that targets specific areas of decline with "Brain Fitness" that targets auditory memory and processing speed and "Insight" that focuses on visual memory and processing speed. Both programs, however, are pricey, at $395. A spokesperson for the company says that the product is worth the price, as it has more science behind it than any other and that its products have been "shown to work."