CCISS: Heart-pounding results from Canadian cardiovascular experiment

The Cardiovascular and Cerebrovascular Control on Return from the International Space Station (CCISS) experiment shows the risks of a sedentary lifestyle

Microgravity in space severely impacts astronauts' bones and muscles, but how does it tinker with the ticker?

In space, blood is not pulled by gravity to the legs, so the heart does not need to work as hard to pump blood throughout the body. This causes blood to gather in the head and chest. Luckily, the body adapts to this change after only a few days, but what happens to astronauts when they return to Earth? Re-entering gravity causes blood to collect in an astronaut's lower body instead, making less blood flow to the brain. In some cases, astronauts get very dizzy; some even pass out from the lack of oxygen-rich blood to the brain.

Getting to the heart of the matter: Astronauts' hearts are affected by the lack of gravity when they arrive in space and by reintroduction to gravity when they return to Earth.

The "gravity" of the situation

The Canadian Space Agency funded a three-year study to gain a better understanding of how astronauts' bodies adapt to long-duration missions aboard the International Space Station (ISS) and to help maintain astronauts' health. Led by Dr. Richard Hughson from the Schlegel-University of Waterloo Research Institute for Aging, the CCISS experiment examined the effects of space flight on the heart.

From to , the astronauts sported devices that tracked their blood pressure, heart rates and physical activity patterns as they performed their daily activities and while they were asleep. The data on the astronauts' vital signs collected from the ISS were then compared to those collected before their space missions.Paper 1

The CCISS research team was the first to use scientific methods to confirm that astronauts have an extremely sedentary lifestyle while in space, and that the removal of the normal daily challenges of moving our bodies against gravity can have negative consequences for the cardiovascular system.Paper 2 Some large differences between astronauts in the way heart rate was controlled by the nervous system were detected during sleepPaper 3 and during simple tests of how heart rate responds to changes in blood pressure.Paper 4

On return to Earth, some astronauts had higher heart rates, and this impacted their ability to control their blood pressure.Paper 4 These results could point to a need for some astronauts to do even more exercise and take other countermeasures to protect their blood pressure regulatory system. Along with the challenges to blood pressure regulation, the CCISS experiment also found reductions in the ability of the blood vessels in the brain to respond to changes in blood pressure.Paper 5

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These published papers are all available as open acess.

Paper 1

Fraser KS, Greaves DK, Shoemaker JK, Blaber AP, Hughson RL. Heart rate and daily physical activity with long-duration habitation of the International Space Station. Aviat Space Environ Med 83: 577-584, PMID: 22764612.

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Paper 2

Hughson RL, Shoemaker JK, Arbeille P. CCISS, Vascular and BP Reg: Canadian space life science research on ISS. Acta Astro 104: 444-448, . doi: 10.1016/j.actaastro.2014.02.008.

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Paper 3

Xu D, Shoemaker JK, Blaber AP, Arbeille P, Fraser K, Hughson RL. Reduced heart rate variability during sleep in long-duration spaceflight. Am J Physiol Regul Integr Comp Physiol 305: R164-R170, PMID: 23637139.

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Paper 4

Hughson RL, Shoemaker JK, Blaber AP, Arbeille P, Greaves DK, Pereira-Junior PP, Xu D. Cardiovascular regulation during long-duration spaceflights to the International Space Station. J Appl Physiol. 112: 719-727, . PMID: 22134699.

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Paper 5

Zuj KA, Arbeille P, Shoemaker JK, Blaber AP, Greaves DK, Xu D, Hughson RL. Impaired cerebrovascular autoregulation and reduced CO2 reactivity after long-duration spaceflight. Am. J. Physiol. Heart Circ. Physiol. 302: H2592-H2598, PMID: 22492717 (related podcast).

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