High temperatures could affect brain function in preadolescents

Exposure to high ambient temperatures is associated with lower connectivity in three brain networks in preadolescents, suggesting that heat may impact brain function. This is the conclusion of a study led by the Barcelona Institute for Global Health (ISGlobal), a center supported by the ”la Caixa” Foundation, and IDIBELL, in collaboration with Erasmus University Medical Center Rotterdam (ERASMUS MC) and the Networked Biomedical Research Center (CIBER): areas of Epidemiology and Public Health (CIBERESP), and Mental Health (CIBERSAM). The results have been published in the Journal of the American Academy of Child & Adolescent Psychiatry. 

The study involved 2,229 children aged 9 to 12 from the “Generation R” cohort in Rotterdam, Netherlands. Functional connectivity data from brain networks, i.e., how different regions of the brain communicate and collaborate, were assessed using resting-state magnetic resonance imaging, when the children were not performing any active tasks. Daily mean temperature estimates were obtained from the UrbClim urban climate model, developed by the Flemish Institute for Technological Research. Temperature values were calculated for the period from 2013 to 2015, assigning daily averages to each participant based on their home address.

Higher ambient temperatures during the week preceding the MRI assessment were associated with lower functional connectivity within the medial parietal, salience, and hippocampal networks, which are essential for proper brain functioning. This implies that brain areas may work less synchronously, affecting processes such as attention, memory, and decision-making. The medial parietal network is related to introspection and self-perception; the salience network detects environmental stimuli and prioritizes what deserves our attention; and the hippocampal network is critical for memory and learning.

The research shows that the association between high temperatures and lower functional connectivity was strongest on the day before the brain scan and progressively decreased on subsequent days. In contrast, low average daily temperatures were not associated with functional connectivity.

“We hypothesise that dehydration could explain our findings, as children are particularly vulnerable to fluid loss when exposed to heat, which can affect the functional connectivity of brain networks,” says Laura Granés, researcher at IDIBELL and ISGlobal and the study's lead author.

“In the current climate emergency, public health policies aimed at protecting children and adolescents from high temperatures could help mitigate potential effects on brain function,” says Mònica Guxens, ICREA researcher at ISGlobal and senior author of the study.

Implications for mental health

Although brain function alterations have been suggested as a possible mechanism linking temperature and mental health, no study to date has examined the effects of ambient temperature on functional brain networks.  In another recent study, the same research team found that exposure to cold and heat can affect psychiatric symptoms such as anxiety, depression and attention problems. In addition, other studies have linked lower connectivity within the brain’s salience network to suicidal ideation and self-harming behaviors in adolescents with depression, as well as to anxiety disorders.

“Given the role of the salience network in suicidal ideation, our findings raise a new hypothesis: high temperatures could decrease the functional connectivity of this network, indirectly contributing to a higher risk of suicide in individuals with pre-existing mental health conditions,” explains Carles Soriano-Mas, researcher at IDIBELL and the University of Barcelona and one of the study's authors. “While we do not propose that these connectivity changes, triggered by heat exposure, directly induce suicidal behaviors, they could act as a trigger in vulnerable individuals,” adds the researcher. 

Reference:

Granés L., Kusters M. S. W., Ballester J., Essers E., Petricola S., López-Vicente M., Iñiguez C., Tiemeier H., Muetzel R. L., Soriano-Mas C., Guxens M. Exposure to Ambient Temperature and Functional Connectivity of Brain Resting-State Networks in Preadolescents. Journal of the American Academy of Child and Adolescent Psychiatry. Doi: https://doi.org/10.1016/j.jaac.2024.11.023