Surprising study shows that healthy brains run hot

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New research shows that healthy brains fluctuate a lot more in temperature than what was previously known. The study has also revealed that brains are generally warmer than other parts of the body. While normal oral temperatures run around 37°C, the average brain temperature can be 38.5°C, with deeper brain regions sometimes more than 40°C. The brain is particularly hot among women throughout the day, according to the study. 

Previous temperature data relied on numbers from intensive care patients, where brain monitoring is essential. Recently, a technique known as magnetic resonance spectroscopy (MRS) has led to non-invasive monitoring in healthy individuals and new data on “normal” brains. For the current investigation, the experts used MRS to monitor how brain temperatures change throughout the day.    

“To me, the most surprising finding from our study is that the healthy human brain can reach temperatures that would be diagnosed as fever anywhere else in the body,” said Dr. John O’Neill, group leader at the MRC Laboratory for Molecular Biology. “Such high temperatures have been measured in people with brain injuries in the past, but had been assumed to result from the injury.”

“We found that brain temperature drops at night before you go to sleep and rises during the day. There is good reason to believe this daily variation is associated with long-term brain health – something we hope to investigate next.”

The scientists used 40 volunteers from the ages of 20 to 40 whose brains were scanned in the morning, afternoon and late evening. The study participants were also given wrist worn monitors to take into account activity levels and individual variations in each person’s “body clock.” 

The results showed that there is an overall higher temperature in the brain with age. The scientists hypothesize that it might be harder for the brain to cool off as we grow older. 

The researchers were able to compare the data from the volunteers to previous medical data and create a map of the human brain, though they say more data is still needed. 

“Using the most comprehensive exploration to date of normal human brain temperature, we’ve established ‘HEATWAVE’ – a 4D temperature map of the brain. This map provides an urgently-needed reference resource against which patient data can be compared, and could transform our understanding of how the brain works,” said Dr. Nina Rzechorzek, MRC Clinician Scientist Fellow from the MRC Laboratory for Molecular Biology who led the study.

“That a daily brain temperature rhythm correlates so strongly with survival after TBI suggests that round-the-clock brain temperature measurement holds great clinical value.”

The scientists hope that their research may be used in the future to better understand and treat brain disorders. 

The research is published in the journal Brain.    

By Zach Fitzner, Earth.com Staff Writer