The lowdown: "In our fast-paced, wired world, many of us live our lives in chronic stress," says Gary Small, MD, director of the UCLA Longevity Center and author of The Alzheimer's Prevention Program. That means we're perpetually bathing our brains in stress hormones like cortisol. The result? Studies done in mice show that chronically elevated stress hormone levels shrink the hippocampus, so you're less likely to form new memories.
The lowdown: In addition to its many other bodily functions, estrogen may help keep women's brains sharp, Dr. Small says. The hormone increases the concentration of an enzyme needed to synthesize the memory-boosting brain chemical acetylcholine and enhances communication between neurons in your hippocampus.
The lowdown: Memory problems are often attributable to (changeable!) lifestyle factors. Take weight: A 2010 study found that for every one-point increase in a woman's BMI (body mass index), her memory score dropped by one point.