By Steven Reinberg
(HealthDay News) -- People exposed to secondhand smoke may face
as much as a 44 percent increased risk of developing dementia, a
new study suggests.
While previous research has established a connection between
smoking and increased risk for dementia and Alzheimer's disease,
this new study is the largest review to date showing a link
between secondhand smoke and the threat of dementia, the authors
"There is an association between cognitive function, which is
often but not necessarily a precursor of dementia, and exposure
to passive smoking," said lead researcher Iain Lang, a research
fellow in the Public Health and Epidemiology Group at Peninsula
Medical School in Exeter, England.
What's more, Lang said, the risk of impaired cognitive function
increases with the amount of exposure to secondhand smoke, the
findings suggest. "For people at the highest levels of exposure,
the risk is probably higher," he said.
The study was published online Feb. 13 in the journalBMJ.com.
For the study, Lang's team collected data on more than 4,800
nonsmokers who were over 50 years old. The researchers tested
saliva samples from these people for levels of cotinine, a
product of nicotine that can be found in saliva for about 25
hours after exposure to smoke.
The study participants also took neuropsychological tests to
assess brain function and cognitive impairment. These tests
evaluated memory, math and verbal skills. People whose scores
were in the lowest 10 percent were classified as having some
level of cognitive impairment.
The researchers found that people with the highest cotinine
levels had a 44 percent increased risk of cognitive impairment,
compared with people with the lowest cotinine levels. And, while
the risk of impairment was lower in people with lower cotinine
levels, the risk was still significant.
"We know that active smoking is bad -- being a smoker is bad
for your health and increases your risk of Alzheimer's. This
study suggests that this is the same for passive smoking," Lang
said. "We know that passive smoking is associated with an
increased risk of stroke and heart disease. This is just another
reason to avoid exposing other people to your smoke, and if you
are not a smoker to stay away from smoking places."
Maria Carrillo, director of medical and scientific relations
for the Alzheimer's Association, said this study offers more
evidence of the dangers of secondhand smoke and the risk for
dementia. Smoking is already recognized as a risk factor for
Alzheimer's, and the risk can be extended to exposure to
secondhand smoke, she said.
"There are findings that secondhand smoke can be just as
detrimental as smoking itself," Carrillo said. "We recommend
that people do not smoke and try to reduce their exposure to
secondhand smoke as well."
Dr. Mark Eisner, an associate professor of medicine at the
University of California, San Francisco, and author of an
accompanying editorial in the journal, said, "This study should
provide further motivation for public policy aimed at making all
public spaces smoke-free."