Figure 1.
Adjusted percent change in heart rate variability indices per interquartile-range increase in prior 4-hour moving average exposure to PM2.5 (particulate matter with an aerodynamic diameter less than 2.5 µm) in single- and 2-pollutant, mixed-effects models, Beijing, China, 2007–2008. Models were adjusted for age, body mass index, gender, time of day, day of the week, visit, temperature, and relative humidity. SDNN, standard deviation of the normal-to-normal intervals; r-MSSD, square root of the mean squared difference between adjacent normal-to-normal intervals; BC, black carbon; NO2, nitrogen dioxide; SO2, sulfur dioxide; CO, carbon monoxide; O3, ozone. Bars, 95% confidence interval.