Rising global temperatures, driven by climate change, have generated a growing array of adverse consequences for human health. A study led by the Harvard T.H. Chan School of Public Health offers compelling empirical evidence on an often-overlooked aspect of this impact: the deterioration of cognitive performance in young, healthy individuals exposed to unconditioned indoor environments during heat waves (Cedeño-Laurent et al., 2018).
Traditionally, studies on the health effects of extreme heat have focused on vulnerable populations—such as the elderly and children—creating the impression that healthy adults would be relatively protected. However, this new field study challenges this assumption by demonstrating that even young college students suffer measurable cognitive impairments when subjected to high temperatures in unconditioned indoor environments. This finding is particularly relevant considering that most adults spend about 90% of their time indoors.
The experiment followed 44 college students in Boston during the summer of 2016, divided between air-conditioned and non-air-conditioned dormitories. For 12 days—five of moderate temperature, five of heatwave, and two of cooling—the participants completed daily cognitive tests upon waking, which assessed executive functions such as processing speed, working memory, and inhibitory control. The results revealed a significant performance impairment among students in the non-air-conditioned buildings. Specifically, these individuals showed a 13.4% increase in reaction time on Stroop tests and a 13.3% decrease in accuracy on arithmetic tests, compared to their counterparts in air-conditioned environments (Cedeño-Laurent et al., 2018).
A particularly alarming finding from the study is that the most pronounced cognitive differences between the groups occurred during the period of external cooling, when outdoor temperatures began to drop, but poorly ventilated buildings continued to retain heat. This suggests that traditional urban architecture, designed to retain heat in cold climates, may act as a “heat trap” in contexts of global warming—prolonging exposure to heat stress even after the heat wave has apparently ended.
This finding reinforces the need to incorporate sustainable architectural and urban solutions adapted to the new climate scenario, such as passive ventilation, materials with high thermal reflectance, and the use of more efficient and affordable cooling technologies. The study also highlights a crucial point in public policymaking: climate risk is not limited to physiological extremes, but includes cognitive deficits with potential impacts on productivity, learning, and decision-making—essential elements for social and economic functioning.
In summary, the work of Cedeño-Laurent and colleagues presents clear and worrying evidence that extreme heat negatively affects cognition even in individuals outside of groups traditionally considered at risk. In times of global warming and increasing urbanization, this type of data not only expands our understanding of environmental risks but also underscores the urgency of rethinking how we inhabit and construct our everyday spaces.
Reference:
CEDEÑO-LAURENT, JG et al. Reduced cognitive function during a heat wave among residents of non-air-conditioned buildings: An observational study of young adults in the summer of 2016. PLOS Medicine, [S. l.], v. 15, no. 7, p. e1002605, 2018. DOI: https://doi.org/10.1371/journal.pmed.1002605. Available at: https://www.sciencedaily.com/releases/2018/07/180711182748.htm. Accessed on: 20 June. 2025.
