By John Gever, Senior Editor, MedPage Today Reviewed by Robert Jasmer, MD; Associate Clinical Professor of Medicine, University of California, San Francisco . Earn CME/CE credit for reading medical news
Dr. Llewellyn and colleagues said earlier research had found an association between passive smoking and the risk of developing dementia, but those findings failed to reach statistical significance after adjusting for age, sex, and education. (See: AAN: Secondhand Smoke Can Add to Dementia Risk)
The researchers said the cognitive impairments seemingly associated with passive smoking may originate with the well-known vascular effects of tobacco. Over a long period, these effects could "compromise the blood supply to the brain," they wrote.
Arguing against that hypothesis was a finding in the current study that the presence or absence of cardiovascular disease, did not affect the results. Nevertheless, said Dr. Llewellyn and colleagues, "exposure to secondhand smoke may interact with subclinical cardiovascular disease."
In an accompanying editorial, Mark D. Eisner, M.D., M.P.H., of the University of California San Francisco, agreed that the study was additional evidence that secondhand smoke can impair brain function.
He also echoed the researchers' call for prospective studies, noting that cotinine was a marker only of tobacco exposure within the last day or so of sampling.
"Although recent exposure probably correlates with longer term exposure, studies that examine the longitudinal effect of self-reported lifetime exposure on cognitive impairment would strengthen the evidence of a causal association," Dr. Eisner said.
He added that, because dementia is such a frightening disorder, more publicity about it as an effect of public smoking may be an effective deterrent.
"Greater public awareness would eventually translate into political action aimed at passing smoke-free legislation in regions of the world where public smoking is still permitted," he contended.
The study was funded by the National Institute on Aging and several agencies of the British government.
No potential conflicts of interest were reported by study authors or the editorialist.