Association between indoor particulate matter with different sizes and their metal components and autonomic nerve function in patients with chronic obstructive pulmonary disease

[Background] Indoor particulate matter (PM) with different sizes may have adverse effects on cardiac autonomic nerve function in patients with chronic obstructive pulmonary disease (COPD), but the association between their chemical components and autonomic nerve function of COPD patients remains unclear. [Objective] This study aims to investigate the association between indoor fine particulate matter (PM2.5) and coarse particulate matter (PM2.5-10) and their metal components and cardiac autonomic nerve function of COPD patients. [Methods] A cross-sectional design was adopted in this study and 43 COPD patients were recruited. From November 2015 to May 2016, heart rate variability (HRV) indices of each patient, including standard deviation of normal-to-normal intervals index (SDNNI), lowfrequency power (LF), high-frequency power (HF), and LF/HF, were gained by dynamic electrocardiogram monitoring for 24 h. Indoor PM2.5 and PM2.5-10 samples were collected for 24 h before health measurement, and 20 metal components were measured by inductively coupled plasma mass spectrometry. The concentration of crustal composition of PM was estimated according to the concentration of main crustal elements. Multiple linear regression model was used to explore the association between indoor PM2.5 and PM2.5-10 and their metal components and HRV indices in COPD patients. [Results] The average concentrations of indoor PM2.5 and PM2.5-10 were (69.24±76.63) μg·m-3 and (34.19±24.10) μg·m-3, respectively. No significant association was observed between indoor PM2.5 and PM2.5-10 concentrations and changes in HRV indices. However, an interquartile range (IQR, 9.67 μg·m-3) increase in crustal composition of indoor PM2.5-10 was associated with a -2.20 (95% CI: -4.12--0.28) change in LF/HF of COPD patients. For metal components of indoor PM2.5, an IQR (1.59 ng·m-3) increase in Cd was associated with a -21.19% (95% CI: -35.65%- -3.49%) change in LF. For metal components of indoor PM2.5-10, an IQR increase of Mg (0.27 μg·m-3), Ca (1.36 μg·m-3), and Sr (5.30 ng·m-3) were associated with increases in HF of 36.64% (95% CI: 3.51%-80.36%), 69.62% (95% CI: 20.15%-139.48%), and 49.74% (95% CI: 3.54%-116.56%), respectively; an IQR increase in Na (0.19 μg·m-3), Mg (0.27 μg·m-3), Ca (1.36 μg·m-3), V (0.98 ng·m-3), and Sr (5.30 ng·m-3), there were changes in LF/HF of -4.93 (95% CI: -8.00--1.86), -3.50 (95% CI: -5.96--1.04), -5.20 (95% CI: -8.32--2.08), -2.12 (95% CI: -4.13--0.10), and -4.29 (95% CI: -7.61--0.97), respectively. [Conclusion] Indoor PM with different sizes and their metal components have different effects on the autonomic nerve function of COPD patients. Compared with indoor PM2.5, the effects of crustal composition of PM2.5-10 and its metal components are more significant.