Weightlessness causes persistent fever in astronauts

Astronauts floating weightlessly through space experience a persisent fever, with their body temperature increasing by about one degree Celsius, according to a study that points out the health implications of space travel. Researchers from Charite - Universitatsmedizin Berlin in Germany used forehead sensors to measure the body temperature of astronauts on the International Space Station (ISS).

The researchers found that the astronauts' core body temperature did not increase suddenly, but that this increase in temperature developed gradually over 2.5 months, eventually reaching approximately 38 degrees Celsius. They found that the astronauts experienced a type of persistent fever; during exercise, the astronauts' body temperature often exceeded 40 degrees Celsius.

"We developed a new technology which combines a skin surface temperature sensor with a heat flux sensor, and which is capable of measuring even minor changes in arterial blood temperature," said Hanns-Christian Gunga from Charite. Using this technology, the researchers measured the
astronauts' core body temperature before, during and after their stays on the ISS, taking readings both at rest and during exercise.

"Under weightless conditions, our bodies find it extremely difficult to eliminate excess heat. The transfer of heat between the body and its environment becomes significantly more challenging in these conditions," said Gunga. In space, sweat evaporates more slowly than on Earth, which shows why astronauts were found to overheat particularly quickly during exercise tests performed on the ISS.

Excessive fluctuations in core body temperature can impair both physical and cognitive performance, and can even be life-threatening. The findings may have positive implications for the health and well-being of astronauts during future long-term space missions, researchers said.

"Our results also raise questions about the evolution of our optimum core body temperature: how it has already adapted, and how it will continue to adapt to climate changes on Earth," Gunga said.

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