Exposure to green space during preconception, pregnancy and postnatal periods may reduce the risk of neurodevelopmental disorders Neurodevelopmental disorders, such as Autism Spectrum Disorder and Attention-Deficit/Hyperactivity Disorder, are increasingly prevalent and are likely influenced by a complex mix of genetic, social, clinical, and environmental factors. While green space exposure has been linked to improved child mental health, its role in young children’s neurodevelopment—particularly before conception and among socioeconomically disadvantaged populations—remains understudied. Emerging research suggests that exposure to green space, especially during sensitive developmental periods, may help protect against the risk of neurodevelopmental disorders. This population-based cohort study investigated how exposure to green space before pregnancy, during pregnancy, and during infancy relates to neurodevelopmental disorders among socioeconomically disadvantaged children in the US.
The study utilized data from 1,841,915 mother–child pairs, accessed from the nationwide Medicaid Analytic Extract (MAX) database. The study population included pregnant women and their liveborn children with birth dates between 2001 and 2014, who were enrolled in Medicaid. Children were followed from birth for up to 14 years until either their Medicaid enrollment ended, they were diagnosed with a neurodevelopmental delay, or the study ended. Green space exposure was quantified using the Normalized Difference Vegetation Index (NDVI) to determine average annual exposures at the maternal residential zip code level. Green space exposure levels were calculated for preconception, pregnancy, and postnatal periods using annual NDVI values to capture critical developmental windows. Cases of neurodevelopmental delays were identified using MAX data, including autism spectrum disorder (ASD), attention-deficit/hyperactivity disorder (ADHD), learning disabilities, speech and language disorders, coordination disorders, intellectual disabilities, and behavioral disorders. Statistical analyses were conducted to examine the relationships between green space exposure and neurodevelopmental disorders. Analysis examined the different exposure windows (preconception, pregnancy, and postnatal) simultaneously and separately to assess potential sensitive periods. Further analyses were conducted to examine a subset of the data for only participants residing in urban zip codes. Analysis also examined differences based on children’s gender, race/ethnicity, urbanicity, and zip code-level socioeconomic status indicators. Finally, to test the robustness of findings, a secondary analysis was conducted using tree canopy cover data (obtained from the National Land Cover Database) as an alternative measure of green space exposure.
Results revealed that “exposure to green space was generally protective for the development of neurodevelopmental disorders.” Living in a greener environment preconception was linked to reduced risks of ASD, ADHD, learning difficulties, intellectual disability, and behavioral disorders. Higher greenness exposure during pregnancy was linked to reduced risks of ASD, learning difficulties, intellectual disability, behavioral disorders, and was slightly protective for ADHD. Further, higher postnatal greenness exposure was linked to reduced risks of ASD, ADHD, learning difficulties, intellectual disability, and behavioral disorders. Analysis of all greenness exposure periods simultaneously revealed some shifts in these relationships. The relationship between postnatal greenness and behavioral disorders was no longer significant. On the other hand, evidence for some relationships was strengthened, such as the links between pregnancy greenness exposure and ASD and preconception greenness and intellectual disability. Analysis of only urban zip codes revealed similar relationships as the main analysis. Some differences based on sex, race, and urbanicity were also identified. Pregnancy greenness exposures were slightly protective in males, but not females, for learning disability and developmental speech or language disorders. Greenness was found to have a stronger protective effect for ASD and learning disability among Black and Hispanic children compared to White children. Greenness also had a stronger protective effect for intellectual disability among Black and Asian children compared to White and Hispanic children. In urban areas, greenness had a protective effect for most neurodevelopmental delays; however, this protective effect was not documented when only rural areas were examined. Findings did not meaningfully differ when tree canopy cover was used as a measure of greenness exposure.
The relationships identified by the study suggest that exposure to greener urban environments during preconception, pregnancy, and postnatal periods may help reduce the risk of neurodevelopmental delays in children. Findings are consistent with those of previous studies. Notably, the protective effects of green space exposure were more pronounced among Black/African American and Hispanic children, as compared to White children, for ASD and learning disabilities. “The stronger protective effects of green space observed among Black and Hispanic children may reflect greater relative benefits in communities with lower baseline access to greenness, higher exposure to environmental and social stressors, and limited availability of other health-promoting resources.” Green space may act as an important protective factor that helps reduce the effects of adversity, strengthens resilience, and supports healthy child development. Overall findings call attention to the developmental benefits of green space and the importance of ensuring equitable access to green space among disadvantaged populations.
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