28 February 2009

Passive smoking

Second-hand cigarette smoke and cognitive impairment
Dementia News (Alzheimer’s Australia): 21 February 2008
There has been Considerable coverage of recently published research into a link between exposure to second-hand cigarette smoke and cognitive impairment. Several media articles have claimed that the research shows that people who are exposed to second-hand smoke are at significantly greater risk of developing dementia than those who are not exposed.

Is this what the published research says?

Before discussing the research it is well to understand a little of the background. Smoking, either actively or passively, is known to increase people’s risk of contracting a number of serious conditions, including diabetes; cardiovascular disease; high blood pressure; and stroke — all of which are risk factors for cognitive impairment and dementia.

So, is it possible that exposure to second-hand smoke could be a preventable risk factor for cognitive impairment?

Dr David Llewellyn and colleagues from the University of Cambridge; the Institute of Public Health in Cambridge; Peninsula Medical School in Exeter; the University of Michigan; and the Veterans Affairs Center for Practice Management and Outcomes Research in Michigan undertook research to investigate the question of whether there was an association between a biomarker of exposure to second-hand smoke and cognitive impairment. A biomarker is a molecular substance used as an indicator of a biological state. The biomarker of interest in this research was cotinine, which is one of the products of nicotine metabolism. It can be found in the saliva of people recently exposed to second-hand smoke and indicates that those people have metabolised nicotine.

The researchers collected saliva samples from 4809 non-smoking adults aged 50 years or more who had taken part in the 1998, 1999, and 2001 waves of the Health Survey for England and who had also participated in the 2002 wave of the English Longitudinal Study of Ageing. Each sample was examined for the presence and concentration of cotinine. Also, a detailed history of smoking and exposure to second-hand smoke was taken from each participant, who was additionally given neuropsychological assessment for cognitive impairment.

The researchers made adjustments for a range of factors that could affect the results, such as age, sex, and education. What they found was that participants who had the highest levels of salivary cotinine were more likely to be cognitively impaired than those exposed to little or no second-hand smoke. Furthermore, there was some evidence of a linear trend, that is, the more second-hand smoke a person was exposed to, the more likely that person was to be cognitively impaired.

Does this mean that exposure to second-hand smoke will significantly increase a person’s risk of developing dementia? At the moment we do not know. The researchers suggest that there may be an association between exposure to second-hand smoke and increased risk of cognitive impairment, but they point out that prospective studies relating cognitive decline and risk of dementia to biomarkers of exposure to second-hand smoke are needed if we are to know with greater certainty. Nevertheless, it would be wise to eliminate or limit our exposure to second-hand smoke, if not because of the possible risks of becoming cognitively impaired and/or developing dementia, then because of the risks of contracting other serious and fatal diseases associated with such exposure.

Study reference:
Llewellyn DJ, Lang IA, Langa KM, Naughton F, Matthews FE. 2009. Exposure to secondhand smoke and cognitive impairment in non-smokers: national cross sectional study with cotinine measurement. British Medical Journal 338: b462.

Also see
Alzheimer’s News posting “Second-hand smoke linked to cognitive impairment” (15 February 2009) for additional references and commentary.

No comments:

Post a Comment

Alzheimer's Australia NSW

Alzheimer's Australia NSW
Alzheimer's Australia NSW

Latest headlines from Library News

Library News

Total Pageviews