May 8, 2007
Need another incentive to stop smoking? You may be harming those around you far more than you may know. Researchers report that long-term exposure to secondhand tobacco smoke, a problem for millions of people who live or work with a smoker, increases the risk of developing dementia.
For the study, researchers evaluated 3,602 people age 65 and older in the Cardiovascular Health Study. Of those, 985 people had no heart disease, no symptoms of Alzheimer's or other forms of dementia, and were never smokers. A total of 495 people reported their lifetime secondhand smoke exposure, with an average of about 28 years of exposure. Then the researchers evaluated which participants developed dementia over a six-year period.
The scientists, reporting at the American Academy of Neurology's 59th Annual Meeting in Boston, found that seniors with high lifetime exposure to secondhand smoke were about 30 percent more likely to develop dementia than those who lived and worked in smoke-free quarters. High exposure was defined as more than 30 years of exposure to secondhand smoke.
"We are still conducting analyses to control for other factors that may be influencing these results, but this finding potentially implicates lifetime exposure to secondhand tobacco smoke as a risk factor for dementia in older adults," said study author Thaddeus Haight of the University of California, Berkeley.
Blood Vessel Damage
Many of those exposed to secondhand smoke showed damage to their blood vessels, including thickened and narrowed carotid arteries in the neck, even if they were free of overt heart disease. Diseased blood vessels, and consequent poor blood flow through them, are a known risk factor for heart disease and strokes.
Damage to blood vessels from various causes may also raise the risk for dementia, studies have found. In the current study, those who showed blood vessel problems from secondhand smoke were nearly two-and-a-half times more likely to develop dementia than those who had healthy arteries.
"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 Haight. "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."
Haight said the study findings provide additional evidence of the hazards of secondhand smoke and provide additional support for policies that seek to reduce the public's exposure to tobacco smoke.
So if you smoke, this is one more reason to quit. Not only can it accelerate mental decline in yourself, earlier studies show. [See the article, "Smoking is Bad for Your Brain, Too."] It can also be bad for the brains of those you love.
Thaddeus J. Haight, Deborah Barnes, Kala Mehta, Kristine Yaffe, et al: "Effects of Second-Hand Smoke and Cardiovascular Disease on Incident Dementia in Participants from the Cardiovascular Health Study." Presented at the 59th Annual Meeting of the American Academy of Neurology, May 1, 2007.