In secondary analyses we tested other potential subject-specific effect measure modifiers but found no consistent differences in associations of VT with air pollutants according to sex, diabetes, obesity (BMI ≥ 30), and medication classes added to the model individually [antiarrhythmic medications, beta-blockers, digitalis and other inotropic agents, statins, and angiotensin I–converting enzyme (ACE) inhibitors) (data not shown)]. This evidence concerns the gene ACE and obesity due to melanocortin 4 receptor deficiency.