Study: Alzheimer's risk spikes 157% with heavy smoking - USATODAY.com

Study: Alzheimer's risk spikes 157% with heavy smoking - USATODAY.com

Heavy smoking in midlife more than doubles your odds of developing Alzheimer's disease, a Kaiser Permanente study said Monday.

The study is the first to examine the long-term consequences of heavy smoking on Alzheimer's and vascular dementia, says the study's principal investigator, Rachel Whitmer, a research scientist with Kaiser Permanente in Oakland.

Researchers evaluated the records of 21,123 men and women, who, starting in midlife, were followed for an average of 23 years. Of 5,367 study participants diagnosed with dementia later in life, 2,367 were smokers, and 261 were heavy smokers (more than two packs a day). Compared with non-smokers, those who had smoked two packs of cigarettes a day increased their risk of developing Alzheimer's by more than 157% and had a 172% higher risk of developing vascular dementia — the second-most-common form of dementia after Alzheimer's. The research is published online in the Archives of Internal Medicine.

Though the study was observational, the authors have theories about what might be going on, Whitmer says. "People who smoke have increased inflammation, and we know inflammation also plays a role in Alzheimer's," she says.

Dementia experts say the new research is strong. "This study is particularly good because it separates out vascular dementia and Alzheimer's," says William Thies, the Alzheimer's Association's chief medical and scientific officer.

"The other novel aspect of it is that they've got a large enough sample to look at different ethnic groups, and it shows smoking's effect on dementia does not differ based on race," says Brenda Plassman, epidemiologist at Duke University Medical Center.

A key question for worried smokers: If I quit, will I lower my risk for dementia? The answer is unknown, but Whitmer says researchers are planning a follow-up study to find out.

The bottom line: "If there's somebody out there who hasn't heard smoking's bad for you, they must live in a cave somewhere," Thies says.

"This is another good reason not to smoke."