Other experts say there is no solid consensus about what "brain health" actually means. Some, like Martek's team of scientists, see it as maintaining cognitive function and reducing the risk of long-term neurological diseases like Alzheimer's and Parkinson's. Others see it from a neurological standpoint and stress the importance of keeping the brain's "network membranes" healthy, because the membranes are the mechanism by which the brain carries out most of its electrochemical communication.
"We used to think of the brain as a machine, with Part A doing Function A and Part B doing Function B," says James Giordano, director of the Center for Neurotechnology Studies at the Potomac Institute for Policy Studies in Arlington, Va., which provides analysis, public advocacy, and private funding for neurotechnology research. "But the brain is actually a bidirectional hierarchical network. We can't say that one particular brain area 'does something.' " In other words, each area of the brain participates with the rest of it to evoke different levels of sensation, cognition, emotion, and consciousness.
Medical experts also define brain health in terms of the brain's ability to learn new things or to perform certain behavioral tasks.
What you can do. Although there may not be a clear definition of what brain health is, there is plenty you can do to keep your brain healthy. U.S. News has covered this aspect of fighting the effects of aging. Lifestyle habits also can help boost your brain smarts.
Medical experts recommend 30 minutes of physical activity a day; teaching the brain new things by playing games, learning new languages, or taking up hobbies; and eating a diet rich in brain-enhancing nutrients—including omega-3s—and fruits and vegetables.
But taking too much omega-3 or other nutritious foods such as almonds or flaxseed oil, could pose a health risk, experts say.
David Perlmutter, a neurologist and expert in the field of nutritional influences in neurological disorders, praises the index but says it leaves out two key tests that people should take to assess their risk of two cognitive ailments. One is a homocysteine blood test, which he says can indicate risk for Alzheimer's disease. The other, he says, is sensitivity to gluten, also known as celiac disease.
"For people that are gluten sensitive, if they eat gluten-containing foods, which are wheat, barley, and rye, it can be a strong cause of dementia," Perlmutter says.
The index's Web site includes a quiz that will test your own brain health and offers individualized recommendations for what you can do to improve it. In addition, it has a U.S. map with easy-to-access information on the reasons behind each state's "brain health" ranking.
The index also identifies the nation's 10 least brain-healthy states.