"There are certain risk factors for dementia that are not modifiable, such as age or family history," she says. "The story that we've been seeing, and the work that we've been publishing, is that the very basic take-home message is what's bad for the heart is bad for the brain. So when you think about risk factors for heart disease, you can also think about those same risk factors for dementia."

Rachel Whitmer's study on the link between smoking and dementia appears in the Archives of Internal Medicine, published by the American Medical Association.