Early life ambient temperature and brain volumes change throughout childhood

Climate change impacts on children's neurodevelopment remain poorly understood, particularly the role of early life temperature exposure on brain development. We investigated the association of heat and cold exposure from pregnancy to 8.5 years with brain structural changes from 9 to 15 years. This study was embedded within the Generation R Study, a birth cohort in the Netherlands. Monthly mean temperature was estimated at participants' addresses, using the high-resolution UrbClim model. Brain volumes were collected from 3,251 children through magnetic resonance imaging scans, performed at 10.1 and 14.0 years. Linear mixed models were used to estimate individual volume changes of 11 brain structures, and distributed lag non-linear models were run to investigate the association between temperature and brain volumes change. Exposure to a monthly mean temperature of 20.5 °C (95th percentile) during pregnancy and infancy was associated with slower thalamic growth. The cumulative effect for exposure to 20.5 °C was -25.80 mm³ [95% CI -42.36, -9.25] for the first pregnancy trimester; -25.60 mm³ [95% CI -41.63, -9.56] for the second trimester, and - 22.92 mm³ [95% CI -37.62, -8.23] for the third trimester. The cumulative effect for the first three months of life was -5.31 mm³ [95% CI -8.90, -1.72]. We did not identify any periods of susceptibility for other brain structures or cold exposure. High ambient temperature during pregnancy and infancy was associated with slower thalamic growth later in childhood, suggesting long-term impacts of heat on thalamic development.