Adjusted percent changes and 95% CIs in (A) nocturnal SDNN and (B) nocturnal HR for an IQR increase in PM2.5 (13.6 μg/m3) by level of oxidative stress and systemic inflammation. Models were adjusted for age, gender, smoking status, use of statin, NSAIDs, hypertensive medication (beta blocker, calcium channel blocker or ACE inhibitors/angiotensin receptor blockers), and aspirin. Diamond blue/red symbols indicate the effect estimate for the upper 20th percentile; diamond white symbols indicate the effect estimate for the lower 80th percentile. P values for interaction effect.