The short-term effects of indoor size-fractioned particulate matter and black carbon on cardiac autonomic function in COPD patients

Background: Previous studies have reported adverse health effects of indoor air pollutants especially particulate matter (PM) and black carbon (BC). Patients with chronic obstructive pulmonary disease (COPD) have been shown to be more likely with cardiovascular comorbidities in which cardiac autonomic dysfunction plays an important role. However, there is little evidence for the effect of indoor PM and BC exposures on cardiac autonomic function in COPD patients. Objectives: To evaluate the association between exposure to indoor size-fractioned PM and BC and changes in HRV and HR in COPD patients. Methods: Forty-three doctor diagnosed, stable COPD patients were recruited and measured for 24-h HRV and HR. Real-time indoor size-fractioned PM and BC were monitored on the day before and the day of performing health measurements. Mixed-effects models were used to estimate the associations between indoor PM and BC and HRV indices and HR after controlling for potential confounders. Results: Increasing levels of size-fractioned PM and BC were associated with decreased HRV indices and increased HR. An IQR (3.14 mu g/m(3)) increase in 8-h BC moving average and an IQR (20.72 mu g/m(3)) increase in 5min PM0.5 moving average concentrations were associated with declines of 7.45% (95% CI:-10.89%,-3.88%) and 16.40% (95% CI: -21.06%, -11.41%) in LF, respectively. The smaller the particles size, the greater effects on HRV indices and HR. Patients' BMI modified the associations between size-fractioned PM and BC and their HRV and HR. For an IQR increase in PM0.5, there was decline in HF of 34.85% (95% CI:-39.08%,-30.33%) in overweight patients, compared to a 2.01% (95% CI: -6.44%, 11.19%) increase in normal-weight patients. Conclusions: Exposures to indoor PM and BC were associated with altered cardiac autonomic function in COPD patients, and the associations for HRV measures of parasympathetic activity (e.g., HF) were more apparent in overweight patients.