Elsevier

Preventive Medicine

Volume 81, December 2015, Pages 195-201
Preventive Medicine

Expired-air carbon monoxide as a predictor of 16-year risk of all-cause, cardiovascular and cancer mortality

https://doi.org/10.1016/j.ypmed.2015.09.001Get rights and content

Highlights

  • EACO is an independent determinant for 16-year all-cause and cancer mortality.

  • Smoking is a better predictor of cardio-vascular mortality than EACO.

  • The effect of EACO is similar in smokers and non-smokers.

  • EACO does not seem to be specific of smoking.

  • EACO could also be a marker of inhaled ambient EACO or endogenous production.

Abstract

Background

Measurement of expired-air carbon monoxide (EACO) is commonly used to ascertain non-smoking status, although it can also reflect exposures not related to smoking. Our aim was to assess 16-year mortality according to EACO measured at baseline, in a general population.

Methods

Our analysis was based on the Third French MONICA population survey (1994–1997). Causes of death were obtained 16 years after inclusion, and assessment of determinants of mortality was based on Cox modeling.

Results

EACO was measured in 2232 apparently healthy participants aged 35-64. During follow-up, 195 deaths occurred (19% were due to cardio-vascular (CV) causes and 49% to cancer). At baseline, the mean EACO was 11.8 (± 7.4) ppm, 4.6 (± 2.5) ppm, 4.3 (± 2.2) ppm for current, former and never smokers, respectively (P < 0.001). After adjustment for main mortality risk factors and smoking, the hazard ratio (HR) for total mortality was 1.03[95% confidence interval: 1.01–1.06] per 1-unit increase in EACO, and it was 1.04[1.01–1.07] for cancer mortality. Adjusted HR for CV mortality was 1.05[1.01–1.10] but did not remain significant after additional adjustment for smoking (0.98[0.91–1.04]). Interactions between EACO and smoking were not significant.

Conclusions

In a general population, baseline EACO is an independent predictor of 16-year all-cause and cancer mortality, after adjustment for confounders including smoking. Given that the effect of EACO is similar among smokers and non-smokers, EACO is probably not solely related to smoking but could also be a marker of inhaled ambient carbon monoxide and/or endogenous production. Besides, smoking better predicts CV mortality than EACO.

Introduction

Expired-air carbon monoxide (EACO) measurement is a simple and cheap method commonly used to ascertain non-smoking status in ex-smokers. However EACO is not only a marker of smoking, it also reflects inhaled ambient carbon monoxide (CO) and endogenous production of CO related to vasoactive, oxidative and inflammatory processes (Durante, 2002, Owens, 2010). Although the health effects of smoking and acute carbon monoxide intoxication are well known, EACO has not been studied so far as a potential predictor of long-term mortality.

The aim of this study was to assess the 16-year risk of all-cause, cardiovascular and cancer mortality according to EACO levels measured at baseline, in a sample selected from the general population.

Section snippets

Study population and design

The study design comprised one single baseline (1994–1997) interview of the participants and one single baseline measurement of EACO and biomarkers. An administrative follow-up was then organized to record vital status of all participants until December 31, 2011. A sample of 3402 subjects was randomly recruited from the general population to participate in the Third French MONICA Cross-Sectional Survey on the prevalence of cardiovascular risk factors (Kuulasmaa et al., 2000, Marques-Vidal et

Results

Table 1 describes and compares the main characteristics of study participants according to tertiles of EACO. EACO was measured in 2232 participants (n = 973 from northern France (Lille), n = 269 from north-eastern (Strasbourg area) and n = 990 from south-western France (Toulouse area)) equally distributed by gender. Mean age was 50 years (± 8 years). At baseline, 46% of participants had never smoked, 27% were former and 27% were current smokers. Mean EACO was 11.8 (± 7.4), 4.6 (± 2.5) and 4.3 (± 2.2) ppm

Discussion

In this study carried out in apparently healthy people recruited from the general population, we showed that, after adjustment for standard risk factors and smoking, baseline EACO is an independent predictor for 16-year all-cause and cancer mortality. Moreover, EACO measurement enhances the performance of the models predicting all-cause and cancer mortality, which suggests that EACO could participate in the mechanisms increasing the risk of all-cause and cancer mortality. On the other hand,

Conclusion

In conclusion, in a general population, after adjustment for confounders including smoking, baseline EACO level is an independent predictor of 16-year all-cause and cancer mortality. Smoking remains a better predictor of CV mortality than EACO. Besides, our results highlight that levels of EACO are not solely related to smoking exposure, but can also reflect ambient carbon monoxide exposure as well as endogenous productions in response to vasoactive, oxidative or inflammatory processes.

Sources of Funding

This work was supported by the " Institut National de la Santé et de la Recherche Médicale" (INSERM), the "Direction Générale de la Santé (DGS)"; the "Institut Pasteur de Lille", the "University Hospital of Lille"; the "Fonds d'intervention en Santé Publique"; the "Mutuelle Générale de l'Education Nationale"; "ONIVINS"; the "Fondation de France"; the "CPAM of Sélestat"; the "Fédération Française de Cardiologie" the "Conseil Régional du Nord-Pas de Calais"; Parke-Davis and Bayer pharmaceuticals;

Conflict of interest statement

The authors declare that they have no conflict of interest

Acknowledgments

We would like to thank all the investigators of the MONICA Project for their contribution to the compilation and validation of the data. We did appreciate the collaboration with the INSEE and the health centers in the 3 regions.

References (18)

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