Climate change heat’s lasting brain risks for children

In a recent study published in Nature Climate Change, researchers investigated the impact of temperature exposure on children’s mental health and cognition during prenatal and early childhood periods.

Their findings indicate that exposure to heat during infancy and toddlerhood and cold during pregnancy and infancy is associated with reduced myelination and maturation of white matter in children’s brains, highlighting the potential long-term neurological risks posed by climate change.

Study: Early life cold and heat exposure impacts white matter development in children. Image Credit: New Africa/Shutterstock.com

Background
Climate change poses significant threats to human health. Global warming is already exceeding 1 °C above preindustrial levels and is projected to reach 1.5 °C by around 2040.

Additionally, climate change has been linked to more extreme cold events, both of which contribute to increased morbidity and mortality.

Children are particularly vulnerable to temperature variability due to their immature thermoregulation mechanisms.

Previous research has shown that both cold and heat exposure can negatively impact children’s health, including their mental health, leading to increased anxiety, depression, and aggressive behavior.

Cognitive functions, such as academic performance, are also affected by extreme temperatures, with some studies indicating long-term impacts on cognitive function and economic outcomes later in life.

However, previous studies have primarily focused on behavioral impacts without examining potential structural changes in the brain.

Given that suboptimal brain structural connectivity, particularly in white matter microstructure, is linked to psychopathological symptoms and cognitive deficits, there is a need to explore how temperature extremes affect brain development.

The rapid growth of white matter in infants and toddlers suggests that these periods may be particularly vulnerable.

About the study
This study aimed to identify critical periods during early life when cold and heat exposure might adversely affect white matter microstructure in preadolescents, addressing a significant gap in the current understanding of the neurological impacts of climate change on children.

The study, embedded within the Generation R Study, a population-based birth cohort in Rotterdam, Netherlands, analyzed the impact of temperature exposure on white matter microstructure in children.

It involved 2,681 children from an initial cohort size of 9,896 pregnancies, focusing on those with higher parental education, Dutch nationality, and higher household income. Exclusion criteria included those born at or before 32 weeks gestation, with incomplete temperature data or poor magnetic resonance imaging (MRI) data.

Temperature exposure was estimated through models, validated against local data, and assessed during pregnancy and childhood.

Specifically, the study used the UrbClim model to estimate ambient temperatures at participants’ residences from conception to preadolescence, with average, minimum, and maximum 4-week mean temperatures recorded at 12.0 °C, −1.1 °C, and 25.2 °C, respectively.

Diffusion tensor imaging (DTI) was employed to assess white matter integrity through mean diffusivity (MD) and fractional anisotropy (FA) in 12 tracts. Neuroimaging data were collected using an MRI scanner, focusing on white matter microstructure.

The statistical analysis utilized Distributed Lag Non-Linear Models (DLNMs) to assess associations between temperature exposure and brain development, adjusting for various confounders.

Findings
The study found that cold exposure (2.6 °C) from the third month of pregnancy to 15 months of life and heat exposure (20.2 °C) from 9 months to 2.6 years were associated with higher MD values at 9–12 years.

Specifically, exposure to 2.6 °C at 6 months of life was linked to a 0.59 × 10⁻⁵ mm²/s increase in MD. No significant association was found between temperature exposure and FA.

The study identified that the susceptibility to temperature effects on MD was most pronounced from the third month of pregnancy to 2.6 years of age, overlapping with rapid white matter development.

It also noted that children in lower socioeconomic status (SES) neighborhoods were more vulnerable to temperature extremes, potentially due to poorer housing conditions and energy poverty.

The findings suggest that cold and heat exposure during critical early developmental periods can negatively impact white matter microstructure, highlighting the importance of considering environmental stressors in early childhood development.

Conclusions
The findings led researchers to conclude that exposure to cold and hot temperatures during pregnancy, infancy, and toddlerhood is associated with higher global MD in children’s brains at ages 9–12, suggesting lasting impacts on white matter microstructure.

No association was found with global FA. However, children from low-SES neighbourhoods are more vulnerable to these temperature effects.

These findings highlight the potential for climate change to exacerbate negative impacts on brain development, emphasizing the need for further research and public health interventions.