Live Longer Happiness plays a pretty important role in keeping your brain healthy and vital, too. Staying positive, say experts, helps fight the "blues." This is good news in terms oflongevity since, among other factors, depression has been shown to increase a person's risk of developing Alzheimer's disease.According to Marion Somers, PhD, a geriatric-care manager in Brooklyn, New York, an optimistic outlook isn't hard to achieve, and doing a few simple "optimism exercises" can yield a big reward. "Optimism exercises don't have to be formal," she says. "You can [improve] your attitude just by taking a brisk walk, petting your dog, or playing with your grandchildren outside." Anything that lets you release pent-up negativity and experience calm, peaceful thoughts can go a long way toward helping you become and stay more positive.Training Your Brain to Stay Positive There are also some specific activities you can undertake to boost your brain's vitality. The ancient practice of yoga, research has found, can improve your cognitive function, including your memory. Registered yoga instructor Jennifer Edwards in New York City says, "Practicing yoga trains your brain to stay focused." It requires you to concentrate on your body's movement in space and the actual mechanics of your breathing, while tuning out distractions. "That focusing," says Edwards, "can improve your brain's ability to function during the day."Yoga also promotes relaxation and eases stress, something David Eagleman, PhD, neuroscientist and assistant professor in the department of neuroscience at Baylor College of Medicine in Houston, Texas, says is very good for your brain's overall health and vitality. "Stress can wear down your brain's cognitive abilities. So anything you can do to eliminate stress will help keep your brain sharp.""Another powerful tool to rev up your brain's vitality is meditation. This technique clears your mind and lets you concentrate on being peaceful," says Dr. Somers. Scientists agree. Researchers at Emory University in Atlanta, Georgia, found regular meditation sessions slowed the normal age-related decline of brain cells. And according to Harvard researchers, daily meditation also reduced normal age-related thinning in regions of the brain thought to be involved in integrating emotional and cognitive processes.Somers says activities like yoga and meditation, which require concentration and focus, are good for your brain in indirect ways, too. "We breathe every day, but, consciously and deliberately thinking about breathing while meditating or doing yoga increases lung function," she says. That increased lung function boosts oxygen levels in blood that circulates through your body, including to your brain. Says Somers, "Oxygen-rich blood keeps the brain healthy and increases alertness."A Vital Spirit, a Lengthy Life Participating in religious or spiritual activities can also keep your brain humming along more smoothly. "The rituals of religious services and the social elements of being part of a congregation stimulate your brain," says Somers. "The sense of belonging and being able to connect with others who share your beliefs heightens alertness, which keeps your brain engaged in daily activities."Being spiritual or religious can also perk up your mental outlook. British researchers found seniors with chronic diseases who attend religious services or who