Weightlessness in Space Causes Astronauts' Blood to Shift

Time in space can impact your body in a variety of ways. Now, scientists have examined these biological effects a bit more closely and have found that in space, the shift of blood and fluid from the lower to the upper body caused by weightlessness is much higher and that blood pressure is much lower than previously thought.

In order to better understand the impacts of living in space, the researchers measured the volume of blood ejected by the heart into the blood vessels and monitored the blood pressure in eight astronauts between the ages of 45 to 53 years during a 24-hour period with portable equipment. The scientists took measurements before, during and then after three to six months of spaceflight. In addition, a blood sample was collected from each astronaut to analyze the nervous regulation of the cardiovascular system.

In the end, the scientists found that the shift of blood is much higher than previously thought. The blood volume burden to the heart was also more than expected, despite the heart rate remaining the same. At the same time, blood pressure was considerably reduced.

"The discovery is important because during long duration missions, the blood volume burden to the heart could constitute a health problem during future long duration missions," said Peter Norsk, lead author of the new study, in a news release. "We know that some astronauts experience vision problems some months into spaceflight and this may in fact be caused by the augmented fluid and blood volume shift to the upper body."

That's not to say that all of the impacts are bad. The lower blood pressure is actually good for the body and the blood vessels. This means that researchers may need to conduct further studies to see what the long term impacts are of these changes.

The findings are published in the Journal of Physiology.

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