By Amy Norton

NEW YORK (Reuters Health) - Older adults who smoke may face an elevated risk of developing Alzheimer's disease, a new study suggests.

In an analysis of two dozen previous studies, UK researchers found that older adults who currently smoked were at greater risk of Alzheimer's than were non-smokers. When the results of the studies were pooled, current smokers had a 79 percent higher risk of the memory-robbing disease.

There was also evidence that smokers had higher risks of other types of dementia, as well as age-related mental decline. However, those links were not statistically significant -- meaning the findings could have been due to chance.

The bottom line, the study's lead researcher told Reuters Health, is that smoking "is likely to be associated with an increased risk of developing Alzheimer's disease."

That should give people one more reason to quit the habit or, better yet, to never start, said Dr. Ruth Peters, of Imperial College London.

She and her colleagues report the findings in the online journal BMC Geriatrics.

Smoking may contribute to dementia in the same way that it affects cardiovascular health -- by damaging the blood vessels and impairing blood flow. As people age, this may accelerate damage to the brain tissue.

On an encouraging note, Peters and her colleagues found that while current smokers had a higher Alzheimer's risk across the studies, former smokers did not.

It's not clear what this means, according to Peters, but it is possible that the excess risk of Alzheimer's declines once smokers quit.

"In any event," she said, "ceasing to smoke is already known to be beneficial in terms of other health outcomes and it is possible that this could apply to dementia also."

SOURCE: BMC Geriatrics, online December 23, 2008.

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