N Rzechorzek/MRC LMB/Brain
Average brain temperatures over a 48-hour period for post-ovulation (luteal) females and males. Women in the luteal phase of the menstrual cycle had around a 0.7°F warmer difference in brain temperatures than men. Brain temperatures across both groups were around 2°F higher than oral body temperatures and varied by time of day. Temperatures were lowest (about 1.6°F lower) at night, just before bed. And regions closer to the brain’s core tended to be warmer than regions measured closer to the cortex.
What is the normal temperature of the human brain? Previous consensus placed brain temperature in line with our body temperature: both at around 98.5°F. But a study published June 13 in Brain found that the temperature of our brains is slightly hotter than our bodies — and it varies throughout the day, across brain regions, throughout the course of our lives. This newfound understanding could help guide future treatments for traumatic brain injuries (TBIs), as patients with moderate to severe TBIs may receive clinical interventions based on monitoring brain temperatures that deviate from the ‘norm’.
Researchers looked at two patient groups to gather data about brain temperatures. The first group included 74 brain injured patients previously recorded from an E.U.-wide TBI database. Then, they recruited another patient group comprised of 40 healthy adults. The team measured participants’ brain temperatures using magnetic resonance spectroscopy (MRS). This technique uses MRI machines to measure the temperature of different parts of the brain.
Researchers found that oral body temperatures in the healthy patient group tended to be around 99.5°F, while their brain temperatures were on average around 101.3°F, an average of 2°F difference between the brain and body. Brain temperatures varied by time of day and was lowest (about 1.6°F lower) at night, just before bed. Temperatures in healthy participants tended to increase a bit with age. Regions closer to the brain’s core also tended to be warmer than regions measured closer to the cortex. Women in the post-ovulation (luteal) phase of the menstrual cycle had slightly higher brain temperatures than men — around a 0.7°F difference between the groups. All together: The researchers hypothesized that daily brain temperature variation better distinguishes temperature function or dysfunction, rather than absolute brain temperature.
Big Picture: This study notes that TBI patients lacking a daily rhythm in brain temperature had a 21 times greater chance of dying in intensive care, hinting that maybe new methods should be developed for temperature monitoring and management. These findings come from relatively small samples of people and will need further confirmation before impacting the clinic. Regardless, the study has us question something we’ve taken as a fundamental fact for some time — reminding us to keep asking questions about the things we think we know about brains.
Read more: Brains can be hotter than the rest of our bodies, especially in women. New Scientist
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