Stress and heart disease have shown an objective link through biomarkers in a new study in the American Journal of Cardiology supported by the MESA Air project. Researchers at UCLA and the University of Washington examined the association between urinary biomarkers of stress (catecholamines and cortisol) and coronary artery calcium (CAC), a validated measure of coronary heart disease directly linked to cardiac health risk, in 654 people part of the MESA cohort. There was a positive association between increased cortisol and increased CAC, and an inverse relationship between dopamine and CAC. No differences were observed between the genders, contrary to the hypothesis. These results highlight the importance of characterizing stress levels as a significant co-factor in the study of heart disease and its relationship to air pollution, in particular.