New research gives new meaning to the term "hotheaded" - your normal brain temperature is higher and varies much more than previously thought.
The findings could lead to future research into whether disruption of daily brain temperature rhythms might trigger dementia and other brain diseases, the study authors said.
The researchers conducted brain scans on 40 volunteers, aged 20 to 40, in the morning, afternoon and late evening of a single day and created the first 4D map of healthy human brain temperature.
The investigators found that the average brain temperature in healthy people is 38.5 degrees Celsius (approximately 101.3 degrees Fahrenheit). This compared with average under-the-tongue temperature of less than 37 degrees C (98.6 F), but that deeper brain regions often exceed 40 degrees C (104 F), particularly in women during the daytime.
Brain temperature was highest in the afternoon and lowest at night.
Brain temperature increased with age, most notably in deep brain regions. The brain's ability to cool down may weaken with age and further research is needed to determine whether that's associated with age-related brain disorders, according to the report published June 12 in the journal Brain.
The study overturns several previous assumptions, particularly the widely held belief that brain and body temperatures are the same.
The researchers also analyzed data from patients with traumatic brain injury and found a strong association between daily brain temperature cycles and survival. Those findings could help improve understanding, prognosis and treatment of brain injury.
The study was led by researchers at the Medical Research Council (MRC) Laboratory for Molecular Biology, in Cambridge, England.
"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. Such high temperatures have been measured in people with brain injuries in the past, but had been assumed to result from the injury," said John O'Neill, group leader at the laboratory.
"We found that brain temperature drops at night before you go to sleep and rises during the day," he added in a news release from UK Research and Innovation. "There is good reason to believe this daily variation is associated with long-term brain health - something we hope to investigate next."
According to study leader Nina Rzechorzek, an MRC clinician scientist fellow, the study "opens a door for future research into whether disruption of daily brain temperature rhythms can be used as an early biomarker for several chronic brain disorders, including dementia."
For more on the brain, go to the U.S. National Institute of Neurological Disorders and Stroke.
SOURCE: UK Research and Innovation, news release, June 12, 2022