Early Heat Exposure May Influence How the Brain Develops

Exposure to high temperatures during pregnancy and early infancy is associated with slower growth of the thalamus later in childhood, according to a study led by the Barcelona Institute for Global Health (ISGlobal). The findings, published in Environment International, suggest that heat exposure during the earliest stages of life may have lasting effects on brain development, ISGlobal said. The study included 3,251 children participating in the Generation R Study, a birth cohort in the Netherlands. Researchers used a high-resolution climate model that provided weekly outdoor temperature estimates during pregnancy and monthly estimates from birth to 8.5 years of age at each participant's place of residence. They then analyzed brain MRI scans performed at around 10 and 14 years of age, said Laura Granés, ISGlobal and IDIAPJGol researcher and first author of the study. Among the brain regions studied, only the thalamus showed a consistent association with early-life heat exposure. The study identified a period of vulnerability spanning pregnancy and the first months after birth. Compared with a reference average temperature of 12.5 degrees Celsius, exposure to monthly mean temperatures of 20.5 degrees Celsius during this period was associated with slower thalamic growth between 9 and 15 years of age. No similar associations were found for other brain structures or for exposure to cold temperatures. Slower thalamic growth was associated with more externalizing behavioral symptoms during adolescence, including aggressive and rule-breaking behavior, though no association was found with cognitive performance. "With global temperatures continuing to rise, measures to reduce heat exposure during pregnancy and early infancy could play an important role in protecting children's brain development," said Mònica Guxens, ICREA Research Professor in ISGlobal and coordinator of the study.