How are the symptoms of long-term exposure to microgravity similar to those of bedridden patients?

Question

A large number of symptoms of long duration stays in microgravity seem to be associated with the headward shift of organs and blood. I've always wondered, couldn't these symptoms also happen in ordinary gravity, by just lying down? If the cause is lack of a vertical gravity gradient, that seems logical. For instance, do long term bedridden patients get puffy face like astronauts?

What are the symptoms caused by long stays in microgravity, and how do they compare to the symptoms experienced by bedridden patients?

Answer 1

There is a very long list of symptoms experienced by astronauts, some of which are related to the microgravity environment and others that are caused by something else. Determining exactly which causes what isn't always straightforward.

In microgravity, blood pools more in the head and upper body than it does on Earth, where gravity pulls it down to your feet. Similarly, the internal organs move upwards towards (or into) the chest cavity. Lying down also removes this gravitational pull towards your feet, so you'd expect the same thing to happen .. except...

Lying down isn't the same as being in microgravity. Imagine a pea in a glass tube. In microgravity, it will float, and a gentle breeze through the tube will cause it to move along the tube. If you lie that tube down on its side here on Earth, however, friction with the tube walls would prevent it from moving.

That said, lying down IS a good analogy for being in microgravity for a lot of conditions, even if it isn't perfect. In 2014, NASA conducted a 70-day bed-rest study, called CFT70, to "test the effectiveness of exercise on loss of muscle, bone and cardiovascular function". As @PearsonArtPhoto has already commented, you can find a first-person write-up of that experiment over at Vice. This wasn't the first such experiment, and it probably won't be the last, either. Some of the results from such studies might surprise you, such as the effects of lying down on your senses of taste and smell or even structural changes in the brain.

Answer 2

In fact, this is something that is an area of exploration. There are a number of studies that simulate weightlessness by forcing the person to lay on a bed 24 hours a day, with the bed at a slight angle. The angle is such that the head is downward, simulating the increase of blood when in microgravity in the upper body. See this article from a journalist who participated in the experiment, as well as this article requesting participants.