Many parts of the country are in the middle of the hottest summer in recent memory. Extreme temperatures are seeing people running for air-conditioned locations, buying fans and trying to stay cool.
Hot days can cause dehydration, heat stroke, sunburn and other health issues, but can it impact your brain? A new study from the T. H. Chan School of Public Health at Harvard University says hot weather affects cognition and brain function.
The study looked at two groups of students, those who lived in dorms with air conditioning and those who lived where there was no AC. The study was one of the first to look at how a heat wave can affect healthy young people. Many studies are done on more fragile patients like the elderly or those with health problems, but the team wanted to see what impact a heat wave would have on a population younger subjects with no adverse health conditions. The study specifically looked at indoor temperatures and cognition. While AC might seem like an unnecessary luxury, the research shows that the lack of cooling inside buildings during a heat wave has a demonstrable effect on brain function.
Jose Guillermo Cedeño-Laurent is a research fellow at Chan and the lead author of the study. He explained, "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. 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."
Extreme heat is a public health concern given the growing challenges of climate change. Among meteorological phenomena, it's the leading cause of death in the United States. Many studies on heat waves and their health impacts consider outdoor temperatures, but looking at temps inside a home, office or dorm is necessary because adults in the US spend an average of 90% of their time indoors.
The research tracked a total of 44 students from their late teens to their early twenties living in dorms in Boston. Twenty-four of the students lived in a high-rise dorm built in the 1990s that had central air conditioning. The remaining students lived in an older dorm, next door to the high-rise, and did not have air conditioning. The students' rooms were set up with monitoring equipment that recorded temperature, carbon dioxide levels, noise levels and humidity. They wore fitness trackers that monitored their activity and sleep patterns as well.
The study period was 12 consecutive days during the summer of 2016. The first few days of the study, temps were seasonal, but not extreme. There was then a five-day long heat wave and two days of cooler temperatures. Upon waking up each day, the students were asked to complete two cognitive tests via an app on their smartphones. The tests measured cognitive speed, focus, and working memory. Students who lived in the buildings with air conditioning did better on all of the tests than their neighbors in the hotter buildings. Reaction time was 13.4% faster in students with AC, and in simple arithmetic exercises, those without AC had scores that were 13.3% lower than the "cool kids."
Another significant finding was that when outdoor temperatures cooled down, the inside temps of the buildings without AC were still hot. Indoor temperatures don't go down as quickly as outdoor numbers because the heat has nowhere to go. Especially in cities like Boston where the architecture is designed to keep heat in for the colder months. For more information on the study, check out the video below.
Sources: T. H. Chan School of Public Health PLOS One Medicine