Exposure to Second-hand Smoke Increases Risk of Cognitive Impairment

February 17, 2009
Julia Ernst, MS

Researchers have discovered that a person’s risk of developing dementia and other types of cognitive disabilities may increase with exposure to second-hand smoke.

Researchers from the University of Cambridge have discovered that a person’s risk of developing dementia and other types of cognitive disabilities may increase with exposure to second-hand smoke.

Dr. David Llewellyn, lead researcher, and his collaborators evaluated saliva samples from almost 5,000 adults over the age of 50 who were non-smokers. The levels of cotinine, a by-product of nicotine, in their saliva and a detailed smoking history, measured the participants’ exposure to second-hand smoke.

The risk of cognitive deterioration increased by 44% in the participants exposed to high levels of second-hand smoke. Neuropsychological tests in verbal memory, numerical calculations, time orientation, and verbal fluency were administered to gauge brain function.

Added together, these results gave researchers a global score for cognitive abilities. The scores in the lowest 10% were then categorized as “suffering from cognitive impairment,” according to a statement on the University of Cambridge’s website.

The study authors proposed several theories as to why second-hand smoke contributes to a higher risk of dementia. A real possibility is the link between second-hand smoke and an increased risk of heart disease and stroke, which are also known to increase the chances of cognitive malfunction and dementia.

Previously conducted studies have shown that active smoking contributes to cognitive issues and dementia. Though other studies have shown that second-hand smoke can impair cognitive development in children and adolescents, this new research is the first to determine that second-hand smoke exposure can also lead to neurological problems in adults.

“Our results suggest that inhaling other people's smoke may damage the brain, impair cognitive functions such as memory, and make dementia more likely,” said Llewellyn. “Given that passive smoking is also linked to other serious health problems such as heart disease and stroke, smokers should avoid lighting up near non-smokers. Our findings also support calls to ban smoking in public places."

To read the abstract of the article printed in the British Medical Journal, click here.