Prenatal green space exposure and child's cognition: mediation by cord blood IGF1 in the ENVIRONAGE birth cohort

BACKGROUND: Green space exposure has been linked to improved cognitive functioning over the life course. We examined whether newborn insulin-like growth factor 1 (IGF1) plays a part in this.

METHODS: We measured cord blood plasma IGF1 in 317 mother-child pairs from the ENVIRONAGE birth cohort. Prenatal green space exposure was assessed within several radii (50-1000 m) around the maternal residence. Multivariable linear regression models were used to associate IGF1 levels with green space exposure. Cognitive functioning was assessed at follow-up at 4 to 6 years of age, using the Cambridge Neuropsychological Test Automated Battery (CANTAB), and converted to components by principal component analysis. Mediation analysis was conducted to examine the relationship between green space exposure and cognitive functioning, with IGF1 as a mediator.

FINDINGS: Prenatal short vegetation (< 3 m in height) exposure associated with newborn IGF1 within 50, 100 and 1000 m (P ≤ 0.05), and newborn IGF1 significantly predicted the neurocognitive domain of attention/psychomotor speed during childhood (P < 0.01). Newborn IGF1 significantly mediated the association between prenatal short vegetation exposure and the latencies of the Motor Screening task and the Big/Little Circle task: Per IQR increase in short vegetation within 50 m, the latencies decreased by 0.45 % (95 % CI: -0.986 to -0.047, P = 0.014) and 0.48 % (95 % CI: -1.164 to -0.016, P = 0.044) via IGF1.

INTERPRETATION: Residential surrounding green space during pregnancy may be associated with long-lasting cognitive benefits for the child, mediated through higher cord blood IGF1 protein levels at birth.