Long-term exposure to ambient PM2.5 and its components and spontaneous abortion: The modifying roles of green space and maternal psychological status.
TL;DR
Long-term exposure to PM2.5 and its components was positively associated with the risk of SAB, and significant effect modification was observed between PM2.5 and its components.
Abstract
Background
Although fine particulate matter (PM2.5) has been linked to spontaneous abortion (SAB), the roles of its components remained unclear, and the potential modifying effects of green space and maternal psychological factors were unknown. In this study, we aimed to explore whether green space and maternal psychological status modify the associations of PM2.5 and its components with SAB risk.
Methods
We included 20,117 pregnant women from Nanjing, China and estimated the average concentration of PM2.5 and its components based on the residential addresses, including nitrate (NO3-), sulfate (SO42-), ammonium (NH4+), black carbon (BC), and organic matter (OM). Green space was indicated by Enhanced Vegetation Index (EVI) and Normalized Difference Vegetation Index (NDVI). The maternal psychological status was assessed using the Self-Rating Anxiety Scale (SAS) for anxiety, the Self-Rating Depression Scale (SDS) for depression, and the Impact of Event Scale-Revised (IES-R) for post-traumatic stress symptoms (PTSD). Multivariable logistic regression combined with propensity score matching (PSM) was applied to estimate the associations of PM2.5 and its components with SAB risk. Two-pollutant models, weighted quantile sum regression (WQS), and Bayesian kernel machine regression (BKMR) were utilized to assess the joint effect of PM2.5 components. Interactions and the Johnson-Neyman method were used to examine the modifying effects of green space and maternal psychological factors.
Results
Long-term exposure to PM2.5 and its components was positively associated with the risk of SAB. After adjustment, each interquartile range (IQR) increase in PM2.5 and its components might increase the odds of SAB (PM2.5, OR = 1.18, 95% CI: 1.11-1.26, P <0.001; NH4+, OR = 1.19, 95% CI: 1.11-1.26, P <0.001; NO3-, OR = 1.18, 95% CI: 1.11-1.26, P <0.001; SO42-, OR = 1.17, 95% CI: 1.10-1.25, P <0.001; OM, OR = 1.14, 95% CI: 1.07-1.21, P <0.001; BC, OR = 1.14, 95% CI: 1.08-1.22, P <0.001). Further adjusting for season of conception, PM2.5 and its components remained significantly associated with the risk of SAB. However, OM (OR = 1.08, 95% CI: 0.99-1.18, P = 0.08) and BC (OR = 1.07, 95% CI: 0.97-1.18, P = 0.19) showed null associations. Significant effect modification was observed between PM2.5 and its components and green space measured by NDVI within a 1000-m buffer (NDVI 1000 m; P for interaction <0.05). In analyses stratified by quartiles of NDVI 1000 m, the association between PM2.5 and SAB was strongest in the lowest greenness quartile and was attenuated or became non-significant in some higher greenness quartiles (Q1, OR = 1.30, 95% CI: 1.14-1.48, P <0.001; Q2, OR = 1.02, 95% CI: 0.90-1.15, P = 0.80; Q3, OR = 1.29, 95% CI: 1.14-1.46, P <0.001; Q4, OR = 1.11, 95% CI: 0.97-1.26, P = 0.12). Higher psychological distress may be associated with an elevated risk of SAB (SDS: OR = 1.90, 95% CI: 1.40-2.56, P <0.001; SAS: OR = 1.01, 95% CI: 1.01-1.02; P <0.001), while no interaction effects were observed.
Conclusions
PM2.5 and its major components, particularly NO3-, NH4+, and SO42-, were associated with an increased risk of SAB. Residential green space, especially NDVI 1000 m, may attenuate these associations, while maternal depressive and anxiety symptoms were independently associated with SAB risk without significant effect modification.