The consequences of climate change for the environment and human health are of concern to both the scientific community and society, and children are particularly vulnerable to these changes due to the immaturity of their thermoregulation mechanisms. A new study has now found that exposure to extreme temperatures during the first years of life can have lasting effects on the microstructure of the brain’s white matter, especially in children living in poor neighborhoods where there is a lack of means to heat or cool the homes.
The research results have been published in Nature Climate Change and highlight the vulnerability of fetuses and children to extreme temperatures. The study has been led by the Barcelona Institute for Global Health (ISGlobal), with the support of the ‘la Caixa’ Foundation, and IDIBELL, in collaboration with the Erasmus University Medical Center Rotterdam (ERASMUS MC) and the Research Center Biomedical Network (CIBER) in the areas of Epidemiology and Public Health (CIBERESP) and Mental Health (CIBERSAM).
“We know that the developing brains of fetuses and children are particularly susceptible to environmental exposures, and there is some evidence that exposure to cold and heat can affect mental well-being and cognitive performance in children.” explains Mònica Guxens, researcher at ISGlobal, Erasmus MC and CIBERESP. “However, there is a lack of studies that evaluate possible changes in brain structure as a result of these exposures,” she adds.
Most significant changes in the brain in the first years of life
The team led by Guxens studied the structure of white matter in the brains of preadolescents to identify critical periods of susceptibility to exposure to extreme temperatures during the first years of life. The analysis included 2,681 boys and girls from the Generation R Study, a birth cohort in Rotterdam, who underwent magnetic resonance imaging (MRI) between ages 9 and 12.
The MRI protocol assessed brain connectivity by measuring water diffusion in the white matter. In more mature brains, water flows predominantly in one direction, resulting in lower values of mean diffusivity and higher values of fractional anisotropy. The researchers used an advanced statistical approach to estimate exposure to monthly mean temperatures from conception to age 8 and its effect on these connectivity parameters at ages 9-12.
The results reveal that exposure to cold during pregnancy and the first year of life, and exposure to heat from birth to three years of age, are associated with greater mean diffusivity in preadolescence, suggesting slower maturation of white matter. .
Participants most exposed to cold and heat show differences in a parameter whose alteration has been related to worse cognitive function and mental health problems
“The fibers of the white matter are responsible for connecting the different areas of the brain, allowing communication between them. As the white matter develops, this communication becomes faster and more efficient. Our study is like a photograph at a certain moment in time and what we see in that image is that the participants most exposed to cold and heat show differences in a parameter – the average diffusivity – that is related to a lower level of maturation of the white matter,” explains Laura Granés, researcher at IDIBELL and ISGlobal and first author of the study. “In previous studies, alteration of this parameter has been related to worse cognitive function and certain mental health problems,” she adds.
“The greatest changes in connectivity parameters are observed in the first years of life,” says Carles Soriano, co-author of the study and researcher at IDIBELL, the UB and CIBERSAM. “Our results suggest that it is during this period of rapid brain development that exposure to cold and heat can have lasting effects on white matter microstructure.”
No association was found between exposure to extreme temperatures and fractional anisotropy at 9-12 years. The scientific team suggests that these metrics reflect different microstructural changes, with mean diffusivity being a stronger indicator of white matter maturation.
Poverty increases vulnerability to extreme temperatures
An analysis stratified by socioeconomic conditions revealed that children from poorer neighborhoods were more vulnerable to extreme temperatures. In these groups, windows of susceptibility were similar to those of the general cohort, but started earlier. These differences may be related to the quality of housing and energy poverty.
One mechanism that could explain the impact of ambient temperature on neurodevelopment is sleep quality. Other possible mechanisms include alterations in placental function, activation of the hormonal axis with increased production of cortisol or inflammatory processes.
“Our findings help raise awareness about the vulnerability of fetuses and children to temperature changes,” says Guxens. The results also highlight the need to design public health strategies to protect the most vulnerable communities from the climate emergency.
Source: Center for Biomedical Research Network (CIBER)
