Secondhand Smoke Increases Dementia Risk

May 15, 2013

Smoking has been linked to a host of ills, including an increased risk for Alzheimer’s disease and other forms of dementia. Now an international study has found that you don’t even have to be a smoker to suffer the deleterious effects of cigarette smoke. Just breathing smoke-filled air can be bad for the brain, the study of nearly 6,000 men and women living in five provinces in China found.

Secondhand smoke, or passing smoking, is known to cause heart disease, lung cancer and respiratory ailments. It has also been linked to thinking and memory problems, but it was unknown if secondhand smoke might be linked to dementia.

This latest study, published in the journal Occupational and Environmental Medicine, found that people exposed to smoky air were at greatly increased risk of “severe dementia,” which would include Alzheimer’s disease and other types of dementia. The study followed 5,921 men and women over 60 living in rural and urban areas of China.

About 10 percent of the study participants had dementia. Being a current or former smoker was linked to an increased risk of having dementia. But so was living with someone who smoked, even if someone has never been a smoker. The longer that someone had been exposed to environmental tobacco smoke, the greater the likelihood of developing dementia.

Dr. Ruoling Chen, a visiting professor at Anhui Medical University and one of the study authors, said, “Passive smoking should be considered an important risk factor for severe dementia syndromes, as this study in China shows. Avoiding exposure to environmental tobacco smoke may reduce the risk of severe dementia syndromes.”

“The increased risk of severe dementia syndromes in those exposed to passive smoking is similar to increased risk of coronary heart disease,” Dr. Chen added.

Other studies have confirmed a link between smoking and Alzheimer’s disease. A study from 2011, for example, found that people who are heavy smokers in middle age have nearly double the risk of developing Alzheimer’s disease in old age. [See the ALZinfo.org story, “Heavy Smoking Increases Alzheimer’s Risk”.] A more recent study found that men who smoke tend to have faster declines in memory as they age than their nonsmoking peers. [See “Smoking Linked to Memory Loss in Men”.]

The current study found that those exposed to secondhand smoke had a 29 percent greater likelihood of developing severe dementia in old age than those who had not been exposed to smoky air. The link is correlational – other factors besides smoke exposure could have contributed to the increased dementia risk. But it does raise troubling questions about passive smoking and Alzheimer’s disease. Given that other studies have found that even living in the same apartment building as someone who smokes may increase health risks, experts agree that it’s a good idea for yourself, and those around you, to stop smoking.

By ALZinfo.org, The Alzheimer’s Information Site. Reviewed by William J. Netzer, Ph.D., Fisher Center for Alzheimer’s Research Foundation at The Rockefeller University.

Source: Chen R, Wilson K, Chen Y, et al. Association between environmental tobacco smoke exposure and dementia syndromes. Occupational and Environmental Medicine. Published online October 26, 2012.


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