Prenatal exposure to air pollution and infant cognitive development using an eye-tracking visual paired-comparison...

Although the prenatal life is a critical period for brain development, very few studies have focused on prenatal exposure to air pollution in relation to infant cognition, and most studies have relied on carer-reported outcome assessment. We examined the association between prenatal exposure to air pollution and objective measurement of infant cognitive development using an eye-tracking methodology. The study was based on data from a subset of 168 mother-child pairs participating in the Barcelona Life Study Cohort (BiSC), Spain (2018-2023). Total exposure to nitrogen dioxide (NO₂), black carbon (BC), particulate matter (PM_2.5), and PM_2.5 copper (Cu) and iron (Fe) content during pregnancy were assessed through integrating estimates of land-use regression (LUR) models with data on time spent at home, workplace, and during commuting. Cognitive performance was assessed longitudinally at 6 months (n = 156) and 18 months (n = 62) of age through an eye-tracking Visual Paired-Comparison (VPC) task that measured short-term recognition memory for faces. Linear mixed models were applied to explore the association between prenatal air pollution exposure and the percentage looking time at novel compared to familiar stimuli on the VPC task, adjusting for potential confounders. Results showed worse cognitive performance with increasing air pollution exposure: For each interquartile range increase of NO₂, BC, PM_2.5, Cu and Fe, novelty preference decreased with -2.0 (95 % CI: 4.7, 0.6), -2.5 (-4.6, -0.5), -3.9 (-7.0, -0.9), -2.1 (-4.0, -0.3), and -1.4 (-3.2, 0.3), respectively. There were suggestions for potentially stronger associations in boys. The findings highlight the pregnancy period as a window of vulnerability for the impact of air pollution on the developing brain, and values eye-tracking as an objective non-invasive tool for early detection of such impact.