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People are beginning to seriously research space travel applications of therapeutic hypothermia, specifically for reducing metabolism and stress on humans traveling to Mars.

It seems that as you decrease the temperature, the metabolism decreases. My question is regarding the relationship between ageing and metabolism. Do we have any data that answers the question if lowered metabolism also lowers the rate of ageing?

I'm wondering if these hypothetical astronauts going to Mars are actually losing 6 months of their lifespan in an unconscious state, or is their ageing rate being lowered as well? And by how much?

For the sake of simplicity, let's ignore the effects of radiation on ageing during the travel.

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Therapeutic hypothermia certainly is an extremely useful short-term treatment for hypoxic and ischaemic injury to tissues (caused by loss of blood flow and/or oxygen) and is part of the protocol for treating people in intensive care who have had out of hospital cardiac or respiratory arrest as well as being used during heart surgery in cardiopulmonary bypass. In addition there is currently research into treating people who have just had heart attacks and strokes, both conditions where there is acute loss of blood flow due to a clot.

However, there is little evidence as regards use of chronic (long term) hypothermia to prevent aging. While severe hypothermia does suppress cellular respiration and slow down metabolism and bodily function, it also often causes other abnormalities such as:

  • Disturbances in cardiac conduction that can lead to cardiac arrest
  • Markedly reduced blood flow to skin and limbs which can lead to tissue death in fingers, toes, etc.
  • Clotting dysfunction (haemorrhage if there is any injury)
  • Pulmonary oedema - fluid in the lungs causing inability to oxygenate and/or ventilate the blood
  • Increase in infections

There is, however, quite a lot more evidence in regards to slowing down cell ageing from oxidative stress using diet energy restriction and this has been replicated in rodents.

In other words, there really isn't any good evidence at this stage in regards to long term hypothermia, but currently, given the high risks of cardiac dysfunction and death, without invasive monitoring and intervention (such as in an ICU) it is not feasible.

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  • $\begingroup$ Interesting. But your last paragraph suggests that invasive monitoring and intervention could perhaps help to achieve long term hypothermia? can you give a little bit more detail on what you are thinking? $\endgroup$ – lurscher Dec 6 '13 at 15:16
  • $\begingroup$ At a minimum you'd need a way to feed the person and dispose of waste- without introducing infection (a major risk of catheters and long term intravenous lines), as well as pacing wires or a defibrillator. You would also probably need a way to monitor blood test results and treat any problems with peripheral circulation and lung problems. Certainly too complex to be automated. $\endgroup$ – Tomcat Dec 7 '13 at 0:07

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