If you’ve been having trouble concentrating or thinking clearly this summer, you’re not alone. Blame the heat.
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That's according to new research from the Harvard T.H. Chan School of Public Health, which found that people suffering through the heat tend to have trouble thinking straight.
"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 heat waves," lead author Jose Guillermo Cedeño-Laurent, said in a university article. "To address this blind spot, we studied healthy students living in dorms as a natural intervention during a heat wave in Boston. Knowing what the risks are across different populations is critical considering that in many cities, such as Boston, the number of heat waves is projected to increase due to climate change."
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For the study, recently published in the journal PLOS Medicine, researchers examined 44 students in their late teens and early 20s in the Boston area for a 12-day period in the summer of 2016 — five days of seasonable temperatures, followed by five days of a long heat wave and then a two-day cool-down.
Of the 44 students, 24 lived in air-conditioned buildings. The others lived in low-rise buildings without A/C.
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To track each room’s atmosphere, researchers measured put a device in each student’s room that measured factors like temperature, carbon dioxide levels, humidity and noise. Wearable devices also measured student physical activity and sleep patterns.
Each day, the students took two cognition tests from their smartphones, the first of which required them to correctly identify the color of displayed words and the second, with basic arithmetic questions.
Together, the tests evaluated cognitive speed, the ability to focus with the presence of irrelevant stimuli and working memory.
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During the heat wave, students without air conditioning experienced decreases in cognitive function, such as 13.4 percent longer reaction times on the first test and 13.3 percent lower scores on the second.
The differences continued into the cool-down period, suggesting the effects of a heat wave linger in buildings.
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"The field study, the first to demonstrate the detrimental cognitive effects of indoor temperatures during a heat wave in a group of young healthy individuals, highlights the need for sustainable design solutions in mitigating the health impacts of extreme heat," the university announced in a news release.
Last year was the warmest year on record for the past two centuries and as global temperatures continue to rise, researchers need to understand the effects of extreme heat and its health impacts on all populations. Additionally, study authors noted, “understanding the effects of indoor temperatures is important given that adults in the U.S. spend 90% of their time indoors.”
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“In regions of the world with predominantly cold climates, buildings were designed to retain heat,” Joseph Allen, co-director for Harvard’s Center for Climate, Health and the Global Environment, said in the school news release. “These buildings have a hard time shedding heat during hotter summer days created by the changing climate, giving rise to indoor heat waves.”
Some limitations of the study, according to the team, include the wide range of students' ages, self-reporting hydration level intakes and the fact that the study was performed in "heating-dominated" climates.
Read the full study at journals.plos.org.