Air pollution and respiratory infections during early childhood: an analysis of 10 European birth cohorts within the ESCAPE Project

Abstract

Background: Few studies have investigated traffic-related air pollution as a risk factor for respiratory infections during early childhood.

Objectives: We aimed to investigate the association between air pollution and pneumonia, croup, and otitis media in 10 European birth cohorts--BAMSE (Sweden), GASPII (Italy), GINIplus and LISAplus (Germany), MAAS (United Kingdom), PIAMA (the Netherlands), and four INMA cohorts (Spain)--and to derive combined effect estimates using meta-analysis.

Methods: Parent report of physician-diagnosed pneumonia, otitis media, and croup during early childhood were assessed in relation to annual average pollutant levels [nitrogen dioxide (NO2), nitrogen oxide (NOx), particulate matter≤2.5 μm (PM2.5), PM2.5 absorbance, PM10, PM2.5-10 (coarse PM)], which were estimated using land use regression models and assigned to children based on their residential address at birth. Identical protocols were used to develop regression models for each study area as part of the ESCAPE project. Logistic regression was used to calculate adjusted effect estimates for each study, and random-effects meta-analysis was used to calculate combined estimates.

Results: For pneumonia, combined adjusted odds ratios (ORs) were elevated and statistically significant for all pollutants except PM2.5 (e.g., OR=1.30; 95% CI: 1.02, 1.65 per 10-μg/m3 increase in NO2 and OR=1.76; 95% CI: 1.00, 3.09 per 10-μg/m3 PM10). For otitis media and croup, results were generally null across all analyses except for NO2 and otitis media (OR=1.09; 95% CI: 1.02, 1.16 per 10-μg/m3).

Conclusion: Our meta-analysis of 10 European birth cohorts within the ESCAPE project found consistent evidence for an association between air pollution and pneumonia in early childhood, and some evidence for an association with otitis media.

Figure 1

Forest plots of individual cohort and combined effect estimates (ORs) by outcome for (A) NO₂, (B) NO_x, (C) PM_2.5, (D) PM_2.5 absorbance, (E) PM₁₀, (F) coarse PM, (G) traffic intensity on nearest street, and (H) traffic load on all major roads. Weight indicates relative weight (%) assigned using random-effects meta-analysis. The lifetime cumulative incidence of respiratory infection (pneumonia, otitis media, croup) was assessed at 12 months (INMA Valencia), 14 months (INMA Gipuzkoa, INMA Sabadell), 15 months (GASPII), 18 months (INMA Asturias), 24 months (BAMSE, GINI/LISA North, GINI/LISA South, PIAMA), and 36 months (MAAS) of age. Individual cohort models were adjusted for municipality (BAMSE), sex, older siblings, breastfeeding at 6 months, atopy of either parent, any child-care reported during follow-up, maternal smoking during pregnancy, any environmental tobacco smoke in the child’s home reported during follow-up, visible mold or dampness in the home, use of gas stove, birth season, parental socioeconomic status (low, medium, high), and intervention (GINIplus, MAAS, PIAMA). Associations are presented for the following increments in exposure: 10 μg/m³ for NO₂, 20 μg/m³ for NO_x, 5 μg/m³ for PM_2.5, 1 unit for PM_2.5 absorbance, 10 μg/m³ for PM₁₀, 5 μg/m³ for coarse PM, 5,000 vehicles/day for traffic intensity on the nearest street; and 4,000 vehicle-km/day for traffic load on major roads within a 100-m buffer.