The association between tobacco smoking and atherosclerotic plaques in the carotid artery is partly mediated by cadmium exposure

Abstract

Exposure to cadmium confers increased cardiovascular risk. Tobacco smoke contains cadmium, which, hypothetically, may mediate parts of the tobacco-associated risk of developing atherosclerotic plaques. Baseline data from the Swedish Malmö Diet and Cancer cohort (1991–1996) were used to test this hypothesis. Mediation analysis was used to examine associations between smoking and blood cadmium levels, and prevalence of ultrasound-assessed carotid atherosclerotic plaques. The total association with smoking status (never-smokers, two categories of ex-smokers, and current smokers) was split into direct and indirect association and the proportion mediated was estimated. The adjusted estimated plaque prevalence was ~27% among never-smokers. We identified both a direct and an indirect pathway between smoking and carotid plaques; the indirect association, through cadmium, was observed among current smokers and ex-smokers who had quit smoking less than 15 years ago. For current smokers, the prevalence ratio for plaque was 1.5, with 60%–65% of the association with smoking being mediated through cadmium. Recent ex-smokers had a prevalence ratio of 1.3, and 40%–45% was mediated through cadmium. Long-time ex-smokers had a prevalence ratio of 1.2, but none of the association was mediated through cadmium. In conclusion, about two thirds of the proatherosclerotic association with smoking was mediated by cadmium.

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