A lack of air conditioning during heatwaves makes people sluggish and more likely to under-perform cognitively, according to new research.
Although the UK has been luxuriating in an ongoing heatwave, the temperature could be hampering productivity.
Scientists from Harvard's TH Chan School of Public Health in the US have published research in a special climate change-focused issue of the PLOS Medicine journal showing how important it is to stay cool.
Using students in dormitories without air conditioning (AC) as the subjects of the study, the researchers demonstrated for the first time the detrimental cognitive effects of indoor temperatures during a heatwave.
The study participants were all young and healthy individuals and highlighted the need for sustainable design solutions in indoor temperature control.
"Most of the research on the health effects of heat has been done in vulnerable populations, such as the elderly, creating the perception that the general population is not at risk from heatwaves," said Jose Guillermo Cedeño-Laurent, the lead author of the study.
"To address this blind spot, we studied healthy students living in dorms as a natural intervention during a heatwave in Boston.
"Knowing what the risks are across different populations is critical considering that in many cities, such as Boston, the number of heatwaves is projected to increase due to climate change."
The study used data collected over 12 consecutive days in the summer of 2016 in which the first five days consisted of normal temperatures, followed by a five day heatwave and a two-day cool-down.
It found that students' houses in dormitories without AC routinely performed worse on cognitive tests than students in air-conditioned housing.
These decreases were measurable across five different areas of cognitive function, including reaction times and working memory.
Students without AC experienced 13.4% longer reaction times on tests which required them to match a colour to a word and 13.3% lower scores in simple arithmetic tests.
"Indoor temperatures often continue to rise even after outdoor temperatures subside, giving the false impression that the hazard has passed, when in fact the 'indoor heatwave' continues," said Dr Joseph Allen.
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He added that even as the heat in the UK appears to be subsiding, it may not be sensible to turn off the AC to save electricity just yet.
"In regions of the world with predominantly cold climates, buildings were designed to retain heat. These buildings have a hard time shedding heat during hotter summer days created by the changing climate, giving rise to indoor heatwaves."