Exposure to Ambient Temperature and Functional Connectivity of Brain Resting-State Networks in Preadolescents.

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Exposure to extreme temperatures has been linked to acute mental-health events in young populations, but the underlying neural mechanisms are not well understood. Resting-state functional magnetic resonance imaging allows for the assessment of connectivity patterns in brain functional networks, which have been associated with mental-health disorders. We investigated the short-term effects of ambient temperature on functional connectivity of brain resting-state networks in preadolescents. The study was embedded in the Generation R Study, Rotterdam, The Netherlands. Daily mean temperature estimates at the participants' residential address were obtained from a high-resolution urban climate model (UrbClim). Resting-state functional connectivity data was assessed with brain magnetic resonance images of 2,229 children aged 9-12 years. We fitted distributed lag non-linear models to assess the cumulative effects of temperature during the week before the brain scan on within- and between-network connectivity of 15 resting-state networks. Higher ambient temperature during the week before the imaging assessment was associated with lower functional connectivity within the medial-parietal, salience, and hippocampus networks. The effect was highest the day before the brain scan, and progressively decayed in the preceding days. Lower temperatures were not related to functional connectivity. Exposure to high ambient temperatures over a seven-day period was associated with lower within-network connectivity in preadolescents, suggesting impacts of heat on brain function. These findings raise new research questions on whether decreases in functional connectivity within the salience network may partially explain the association between high temperatures and suicide rates previously reported in the literature.