Association of multiple air pollutants exposure with heart rate variability in children: From two panel studies

Air pollution has been associated with adverse cardiovascular effects in adults, but its impact on children's heart rate variability (HRV) is unclear.

We conducted two longitudinal panel studies among 271 children aged 4-13 years and each with up to three repeated visits over three distinct seasons within one year. Each visit occurred in a separate season. Personal real-time PM_2.5 exposure was measured 72-h preceding each HRV assessment. Residential NO₂ and O₃ levels were estimated using random forest modeling, while SO₂ and CO were from the China High Air Pollutants. Linear mixed-effects, bayesian kernel machine regression (BKMR) and weighted quantile sum (WQS) regression were employed to assess the association between air pollution and HRV.

The strongest inversely dose-response associations emerged for O₃ with root mean square of successive differences in adjacent NN intervals (RMSSD), low-frequency power and high-frequency power (HF), and NO₂ with HF at lag 0 (physical examination day). Even when O₃ was below Chinese Ambient Air Quality Standard Grade I (CAAQS I) (<100 μg/m³), its adverse association with HRV remained significant. BKMR and WQS indicated that co-exposure to PM_2.5, NO₂, O₃, SO₂ and CO was associated with decreased RMSSD and HF, with O₃ contributing the most. Each quartile increase in the mixture was related to RMSSD and HF decreasedby 2.82 % (95 % CI: 0.73 %, 4.90 %) and 5.84 % (95 % CI: 0.85 %, 9.61 %), respectively. Additionally, the detrimental effect of O₃ on HF was stronger in children with PM_2.5 levels exceeding CAAQS I (≥35 μg/m³) and overweight/obesity.

Short-term air pollution exposure showed dose-response associations with decreased pediatric HRV, with O₃ and NO₂ as key contributors.