Brain scans of over 2,000 preteens demonstrate that early exposure to heat and cold can impact the white matter in their brains, particularly in underprivileged communities. This significant study, published in Nature Climate Change, underscores the vulnerability of fetuses and children to extreme temperatures.
In the current climate crisis, the effects of extreme temperatures on health are a big concern. Children are especially at risk because their bodies can’t yet regulate temperature.
The developing brains of fetuses and children are sensitive to environmental factors, and some evidence suggests that exposure to cold and heat might affect mental health and cognitive performance. However, few studies have examined how these exposures change brain structure.
Guxens’ team studied the white matter in the brains of preteens to see how early exposure to cold and heat affects it. They analyzed 2,681 children from the Generation R Study in Rotterdam who had brain MRIs between ages 9 and 12.
The MRIs measured brain connectivity, focusing on water flow in white matter, which changes as the brain matures. They estimated each child’s exposure to monthly temperatures from conception to age eight and its effect on brain connectivity in MRIs.
The results show that cold exposure during pregnancy and the first year and heat exposure from birth to age three are linked to slower white matter maturation in preteens, indicated by higher mean diffusivity. In this study, ‘cold’ and ‘heat’ are defined as temperatures at the lower and upper extremes in the study area.
White matter fibers connect different brain areas, enabling faster communication as they develop. The study shows that children exposed to extreme temperatures have higher mean diffusivity, indicating slower white matter maturation. This parameter is linked to poorer cognitive function and some mental health issues.
The most significant changes in brain connectivity happen in the first years of life. Results suggest that cold and heat exposure during this critical period can have lasting effects on white matter development.
There was no link between early temperature exposure and fractional anisotropy at ages 9-12. The authors believe this is because the two metrics reflect different brain changes, with mean diffusivity being a more reliable indicator of white matter maturation.
Analysis by socioeconomic conditions showed that children in poorer neighborhoods are more vulnerable to cold and heat exposure. These children had similar sensitive periods to the overall group. However, they started earlier, possibly due to poor housing and energy poverty.
Poor sleep quality might explain how temperature affects brain development. Other possible reasons include problems with the placenta, increased cortisol production, and inflammation.
Mònica Guxens, a researcher at ISGlobal, Erasmus MC, and CIBERESP, said, “Our findings help to raise awareness of the vulnerability of fetuses and children to changing temperatures. The findings also stress the need to design public health strategies to protect the most vulnerable communities in the face of the looming climate emergency. “
Journal reference:
- Granés, L., Essers, E., Ballester, J. et al. Early life cold and heat exposure impacts white matter development in children. Nature Climate Change. DOI:10.1038/s41558-024-02027-w.