Particulate matter air pollution and reduced heart rate variability: How the associations vary by particle size in Shanghai, China

Abstract

BackgroundIt remains unclear which size of particles has the strongest effects on heart rate variability (HRV). ObjectiveTo explore the association between HRV parameters and daily variations of size-fractionated particle number concentrations (PNCs). MethodsWe conducted a longitudinal repeated-measure study among 78 participants with a 24-h continuous ambulatory Holter electrocardiographic recorder in Shanghai, China, from January 2015 to June 2019. Linear mixed-effects models were employed to evaluate the changes of HRV parameters associated with PNCs of 7 size ranges from 0.01 to 10 μm after controlling for environmental and individual confounders. ResultsOn the concurrent day, decreased HRV parameters were associated with increased PNCs of 0.01–0.3 μm, and smaller particles showed greater effects. For an interquartile range increase in ultrafine particles (UFP, those < 0.1 μm, 2453 particles/cm3), the declines in very-low-frequency power, low-frequency power, high-frequency power, standard deviation of normal R-R intervals, root mean square of the successive differences between R-R intervals and percentage of adjacent normal R-R intervals with a difference ≥ 50 ms were 5.06% [95% confidence interval (CI): 2.09%, 7.94%], 7.65% (95%CI: 2.73%, 12.32%), 9.49% (95%CI: 4.64%, 14.09%), 5.10% (95%CI: 2.21%, 7.91%), 8.09% (95%CI: 4.39%, 11.65%) and 24.98% (95%CI: 14.70%, 34.02%), respectively. These results were robust to the adjustment of criteria air pollutants, temperature at different lags, and the status of heart medication. ConclusionsParticles less than 0.3 μm (especially UFP) may dominate the acute effects of particulate air pollution on cardiac autonomic dysfunction.