People who smoke in middle age - particularly heavy smokers - significantly increase their risk of dementia decades later. That's the message from the newly-published results of a large, long-term study.
The smoking habits of more than 21,000 California residents were surveyed in the 1970s and 1980s. Years later, their medical records were reviewed for diagnosis of Alzheimer's Disease and other forms of dementia.
Rachel Whitmer of the Kaiser Permanente Division of Research says that heavy smokers in the study - those who smoked at least 40 cigarettes, or two packs a day - doubled their risk of dementia over an average follow-up of 23 years.
"But the story wasn't limited just to very heavy smokers," says Whitmer. "Even folks who reported smoking one to two packs a day had a 44 percent greater risk of dementia. And people who reported smoking a half pack to one pack per day had a 37 percent greater risk of dementia."
The reason heavy smokers are more likely to suffer dementia later in life is unclear, and may involve multiple factors.
Whitmer, who has published previous studies linking dementia to other risks such as obesity and high blood pressure, sees a pattern.
"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.