Further Information

Cotinine as a marker of exposure to lifestyle risk factors other than smoking | Jan Hamling, Peter N Lee, John S Fry
Article Published: 1998

Type: Meta-Analysis
Further Information

The use of cotinine in non-smokers as a marker for exposure is and has been widely used in passive smoking studies. The implication is that exposure = risk, thus that exposure = harm.

The existence of this portal is, in itself, a demonstration of the falsity of that statemen, and we will not belabour this here. Rather, the questions are: is cotinine a reliable indicator of risk? Is it unique of tobacco smoking? Does it indicate risk that is solely coming from tobacco smoke?

Using two representative UK surveys which determined cotinine in serum (HSE93) or saliva (HALS2), we related 32 risk factors to cotinine level in never and current smokers.

Using the same 4813 HSE93 and 3668 HALS2 subjects, we compared the associations with cotinine with those with the indices “living with a smoker” and “number of cigarettes smoked per day”. In never smokers, cotinine was strongly positively associated with numerous risk factors, including low social class, lack of education, low income, having a “risky” occupation, high alcohol and fried food consumption, high body mass index, low control at work and high extroversion. Associations were generally stronger with cotinine than with living with a smoker.

In current cigarette smokers, cotinine was strongly positively associated with lack of education, low social class, long time before first meal, high fried food, tea and coffee consumption, low fruit and salad consumption, using sugar in tea and coffee and low control at work. Number of cigarettes smoked marked some associations better than cotinine, but others worse. High alcohol consumption and body mass index were weakly positively associated with number smoked but were clearly negatively related with cotinine, which may indicate an effect of these risk factors on inhalation or metabolism of nicotine.

Cotinine is a marker of exposure to many risk factors other than tobacco smoke. These correlations could confound studies of the health effects of smoking, especially passive smoking.

Cotinine, whether measured in serum, saliva, urine or other tissues or body fluids, has been widely used as a marker of recent exposure to tobacco smoke constituents. Numerous large studies show that average cotinine levels differ markedly between current smokers and nonsmokers, that cotinine levels in current smokers are correlated with self-reported number of cigarettes smoked per day and that cotinine levels in nonsmokers are correlated with various questionnaire indices of ETS exposure. As a measure of exposure to tobacco smoke, cotinine has the important benefit of being objective, but the disadvantage of measuring only recent exposure when past or total lifetime exposure may be necessary to assess health effects.

Our group previously described results of analyses based on the Health and Lifestyle Survey (HALS1) comparing the prevalence of 33 lifestyle factors generally considered associated with adverse health between current smokers, ex-smokers, never-smokers living with a smoker (“passive smokers”) and other never smokers. Of the 33 risk factors, 27 showed a significantly higher prevalence in heavy smokers than in never smokers and only two showed a lower prevalence. For many risk factors, prevalence increased with amount smoked, decreased with time of smoking cessation and was increased in passive smokers. The magnitude of bias from confounding by the risk factors was estimated and it was concluded that confounding by multiple risk factors may be an important issue in smoking studies where weak associations are observed.

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