Scientists have exposed a possible link between second-hand smoke and dementia.

Research published in bmj.com claims to be the first large-scale study to conclude exposure to second-hand smoke could lead to neurodegenerative conditions.

A possible link between active smoking and cognitive impairment has already been established and previous findings also suggest that second-hand smoke exposure could be linked to poor cognitive performance in children and adolescents.

The authors of today's study, Dr David Llewellyn and his research team from the University of Cambridge, Peninsula Medical School and the University of Michigan, examined saliva samples from almost 5000 non-smoking adults over the age of 50 using data from the 1998, 1999 and 2001 waves of the Health Survey for England (HSE).

The samples were tested for cotinine - a product of nicotine that can be found in saliva for about 25 hours after exposure to second-hand smoke.

Participants in the study also provided a detailed smoking history. Non-smokers and previous smokers were assessed separately.

The researchers used established neuropsychological tests to assess brain function and cognitive impairment. These focused on memory function, numeracy and verbal fluency - for example naming as many animals in a minute. The results of the tests were added together to provide a global cognitive function score.

Participants whose scores were in the lowest ten per cent were defined as suffering from some level of cognitive impairment.

The authors argue that the link between second-hand smoke and cognitive impairment could be explained given that heart disease increases the risk of developing dementia and second-hand smoke exposure is known to cause heart disease.

Writing an accompanying editorial, Dr Mark Eisner from the University of California, said the serious negative health effects of second-hand smoke like cancer and premature death are beyond doubt, but there is still a lot to learn about scale of illnesses caused by it.

"Emerging evidence suggests that parental smoking may impair childhood cognitive development," he wrote.

"Later in life, second-hand smoke may cause cardiovascular disease and stroke, which are themselves linked to cognitive decline. Until now, however, the suspicion that passive smoking is bad for the adult brain had not been scientifically confirmed."


© Adfero Ltd

More Essential News