That half-used bottle of ginkgo biloba in the medicine chest? You can probably toss it. The stack of crossword and Sudoku puzzles by your chair? Fine if you enjoy them, but don't force yourself to slog through them like your 10th-grade homework. The treadmill in the basement? Keep on treading -- not only is physical exercise good for your heart and waistline, but it just might help keep your brain in shape, too.
That's the latest advice for keeping your mind sharp as you get older, based on what scientists know so far; unfortunately, that's not much.
Researchers have found little proof that any factors within our control can help ward off Alzheimer's disease, diminish dementia or preserve our ability to form memories, make decisions and learn new information.
"If you drill down into the hard-nosed, scientific studies, if you say, 'Show me that you can prevent Alzheimer's by doing A, B or C,' you just can't do it," said Dr. Ronald C. Petersen, director of the Alzheimer's Disease Research Center at the Mayo Clinic in Rochester. "The data are not that convincing for any single intervention."
This might come as a surprise to anyone who watches TV, reads magazines or surfs the Internet. There's plenty of advice: Eat more berries (or fish, or curry). Take Vitamin E. Get more sleep. Meditate. Drink one glass of wine a day. Have an active social life. Think positive thoughts.
Often these prescriptions for brain health are presented as if backed by incontrovertible proof. But real evidence is lacking, according to an independent panel of doctors and experts who met last year at a conference organized by the National Institutes of Health. After examining research and hearing from investigators in the field, the panel wrote that, for now, "firm conclusions cannot be drawn about the association of any modifiable risk factor with cognitive decline or Alzheimer's disease."
Those helpful tips in the media are generally based on studies showing correlation between brain health and other factors. But those studies -- most of them small, methodologically flawed, inconsistent or limited by practical constraints -- don't actually prove that those factors are what caused the healthy minds.
For example, researchers have observed that people who are socially active are more likely to be mentally sharp. Is this because social activity stimulates the brain and forestalls cognitive impairment? Or is it that people who are mentally agile enjoy getting together with friends and family, while their peers who have trouble following a conversation are inclined to withdraw? A team from Duke University combed through 25 years of research, examined nearly 300 studies, then reported that hardly any of them indicated which direction the causal arrow points.
