Brain's White Matter Affected by Early Life Temperature Variations, Study Finds

New research, published in the journal Nature Climate Change, found that children and fetuses exposed to hot and cold environments impact their brain's white matter, responsible for connecting various brain regions and enabling communication.

Researchers said that children are especially vulnerable to extreme environments as their bodies' temperature regulation processes are still immature. They also found that early exposure could have lasting effects on the microstructure of white matter in the brain.

"We know that the developing brain of fetuses and children is particularly susceptible to environmental exposures, and there is some preliminary evidence suggesting that exposure to cold and heat may affect mental well-being and cognitive performance in children and adolescents. However, there is a lack of evidence with regards to how such exposure can bring about structural changes in the brain," said lead researcher Monica Guxens.

In the study, researchers examined the exposure of nearly 2,700 preteens to monthly temperatures from birth until they turned eight years old, utilizing magnetic resonance imaging (MRI) brain scans. The impacts of this exposure were assessed between the ages of nine and twelve by evaluating the preteens' white matter connectivity through the measurement of water flow and spread in their brains, known as 'mean diffusivity'.

Previous studies have shown changes in mean diffusivity to be related to poorer cognitive function and mental health problems.

The results showed that exposure to colder-than-usual temperatures during pregnancy and the first year of life, and exposure to hotter-than-usual environments from birth until three years of age were linked with meaner diffusivity at pre-adolescence, pointing to a slower maturation of their white matter.

“The fibers of the white matter connect different areas of the brain, facilitating communication between them. As white matter develops, this communication becomes faster and more efficient. Our study reveals that participants who were more exposed to extreme cold and heat show differences in mean diffusivity, a parameter linked to a lower level of white matter maturation,” said the study authors.

Reference: Granés, L., Essers, E., Ballester, J. et al. Early life cold and heat exposure impacts white matter development in children. Nat. Clim. Chang. (2024). https://doi.org/10.1038/s41558-024-02027-w