Secondhand Smoke Linked to Dementia

Living with a smoker can make people 2.5 times more likely to develop dementia than residing with non-smokers, say U.S. doctors.

This is one of the first studies to look at the risk of dementia in people who never smoked, but were exposed to secondhand smoke, said Thaddeus Haight, a senior statistician at the University of California at Berkeley.

These results show that secondhand smoke is associated with increased risk of dementia, even in people without known risk factors for dementia related to diagnosed cardiovascular disease, he said at the 59th annual meeting of the American Academy of Neurology in Boston.

Haight identified 985 subjects from the sub-study on cognitive function of the Cardiovascular Health Study. The subjects were mostly women, ages 70 to 74, and at enrollment, the subjects had no underlying dementia, no clinical cardiovascular problems and were non-smokers.

He scrutinized results after six years and found that the subjects who progressed to dementia tended to have underlying cardiovascular disease as determined by ultrasound examination of the carotid arteries in the neck — and lived with a smoker for more than 30 years.

He found little correlation between dementia and living with a smoker for less than 30 years.

Haight said people with the greatest underlying cardiovascular risk who lived with smokers for longer than 30 years were about 2.5 times more likely to have developed dementia than those who had the lowest cardiovascular problems and had lived with a smoker for less than 30 years.