Exposure to Secondhand Smoke and Biomarkers of Cardiovascular Disease Risk in Never-Smoking Adults

Abstract

Background— Exposure to secondhand smoke has been associated with a disproportionately high risk of coronary heart disease, thought to be mediated through inflammation, platelet aggregation, and/or endothelial dysfunction. The epidemiological association between objectively measured exposure to secondhand smoke and biomarkers of heart disease risk has not been investigated, however. Methods and Results— We have investigated the cross-sectional relation between secondhand smoke exposure, measured objectively as cotinine, and recognized biomarkers of heart disease risk, namely C-reactive protein, homocysteine, fibrinogen, and white blood cell count, in 7599 never-smoking adults from the Third National Health and Nutrition Examination Survey. Compared with subjects with no detectable cotinine, those with detectable but low-level cotinine (range, 0.05 to 0.215 ng/mL) had significantly higher levels of both fibrinogen (adjusted mean difference, 8.9 mg/dL; 95% CI, 0.9 to 17.0; P =0.03) and homocysteine (0.8 μmol/L; 95% CI, 0.4 to 1.1; P <0.001) but not C-reactive protein or white blood cell count. Effect estimates of similar magnitude and significance were seen in subjects in the high category of cotinine exposure (>0.215 ng/mL). The increased levels of fibrinogen and homocysteine seen in relation to secondhand smoke exposure were equivalent to ≈30% to 45% of those seen for active smoking. Conclusions— Passive smokers appear to have disproportionately increased levels of 2 biomarkers of cardiovascular disease risk, fibrinogen and homocysteine. This finding provides further evidence to suggest that low-level exposure to secondhand smoke has a clinically important effect on susceptibility to cardiovascular disease.