[Short-term effects of household indoor- and outdoor-originating fine particulate matters on heart rate and heart rate variability in chronic obstructive pulmonary diseases patients, Beijing].

Objective To assess the associations of indoor fine particulate matter (PM2.5) from outdoor and indoor sources with heart rate (HR) and heart rate variability (HRV) in patients with chronic obstructive pulmonary disease (COPD) of Beijing. Methods A total of 40 male patients in a stable stage of COPD were recruited from a hospital in a panel study in Beijing with 5 consecutive days of measurement for each subject. General information and disease history of the participants from questionnaires were obtained prior to the study. HR and HRV were repeatedly examined using dynamic electrocardiograph. HRV included standard deviation of all NN intervals (SDNN), root mean square of successive differences between adjacent NN intervals (rMSSD), total power (TP) power in the low-frequency band (LF) and the high-frequency band (HF). Iron was used as tracer element to separate indoor-originated PM2.5 and outdoor-originated PM2.5. Mixed-effect models were applied to assess the associations of outdoor-originated PM2.5 or indoor-originated PM2.5 and health effects. Results The P50 (P25, P75) values of daily indoor PM2.5, indoor-originated PM2.5 and outdoor-originated PM2.5 were 50.9 (26.8, 122.7), 16.0 (1.9, 43.7) and 27.3 (13.5, 61.8) μg/m3, respectively. The mean±SD of concentrations of real-time indoor PM2.5, indoor-originated PM2.5 and outdoor-originated PM2.5 were (61.5±58.8), (25.3±39.1) and (36.2±42.7) μg/m3, respectively. Compared with outdoor-originated PM2.5, indoor-originated PM2.5 had significant associations with HRV and HR. Each 10 μg/m3 increase at 4 h indoor-originated PM2.5 and outdoor-originated PM2.5 moving average was associated with 3.4% (95%CI: -4.7%, -2.1%) and 0.6% (95%CI: -2.0%, -0.8%) reduction in TP (P<0.001). Each 10 μg/m3 increase at 12 h indoor-originated PM2.5 moving average was associated with 7.6% (95%CI: -10.1%, -5.1%), 4.7% (95%CI: -6.7%, -2.7%), 3.3% (95%CI: -4.2%,-2.4%) and 3.0% (95%CI: -4.5%, -1.5%) reduction in HF, LF, SDNN and rMSSD, respectively. Each 10 μg/m3 increase at 12 h outdoor-originated PM2.5 moving average was associated with 0.7% (95%CI: -2.7%, -1.4%), 0.2% (95%CI: -1.9%, 1.4%), 0.7% (95%CI: -1.4%, -0.1%) and 0.2% (95%CI: -1.3%, 0.9%) reduction in HF, LF, SDNN and rMSSD, respectively (P<0.001). Each 10 μg/m3 increase at 8 h indoor-originated PM2.5 and outdoor-originated PM2.5 moving average was associated with 0.7% (95%CI: 0.4%, 1.0%) and 0.4% (95%CI: 0.2%, 0.6%) increase in HR. Conclusion Exposure to indoor-originated PM2.5 was more strongly associations with HRV indices and HR compared with outdoor-originated PM2.5 in male COPD patients. Key words: Particulate matter; Air pollution, indoor; Pulmonary disease, chronic obstructive; Heart rate variability