10 / 2023-04-06 16:14:50

Improved ambient air quality is associated with decreased prevalence of childhood asthma and infancy shortly after weaning is a sensitive exposure window

Particulate Matter, Infancy, Asthma And Wheezing, Exposure Window, Breastfeeding

Background: The urban ambient air quality has been largely improved in the past decade. It is unknown whether childhood asthma prevalence is still increasing in ever top-ranking city of Shanghai, whether the improved air quality is beneficial for children’s asthma and what time window of exposure plays critical roles.

Objective: Identify the sensitive exposure window (SEW) for particulate matter exposure associated with childhood asthma and observe the dynamic association between breastfeeding and SEW.

Methods: Using a repeat cross-sectional design, we analyzed the association between early life particles exposure (resolution 1km x 1km) and asthma/wheezing first attack in a two-stage retrospective study in 2011 and 2019 in 11,825 preschool children in Shanghai.

Results: A significantly lower prevalence of doctor diagnosed asthma (DDA)(6.6% vs. 10.5%, P <0.001) and wheezing(10.5% vs. 23.2%, P <0.001) was observed in 2019 compared to 2011. Exposure to fine particulate matter (PM_2.5), coarse particles (PM_2.5-10) and inhalable particles (PM₁₀) was decreased in 2019 by 6.3%, 35.4% and 44.7% in uterus and 24.3%, 20.2% and 31.8% in infancy, respectively. Regression analysis showed exposure in infancy had independent association on DDA first attack adjusting for exposure in uterus. For each interquartile range (IQR) increase of infancy PM_2.5, PM_2.5-10 and PM₁₀ exposure, the odds ratios were 1.39 (95% Confidence Interval (CI):  1.24-1.56), 1.51 (95%CI: 1.15-1.98) and 1.53 (95%CI: 1.27-1.85), respectively. The Distributed Lag Non-linear Model showed the SEW was 5.5-11months after birth. Stratified analysis showed the SEWs were at or shortly after weaning, but only in those with <6 months of exclusive breastfeeding.

Conclusions: Improved ambient particulate matter benefits in decreasing childhood asthma longitudinally. We firstly reported the finding of SEW to particulate matter at or closely after weaning on childhood asthma.