What would happen to your body if you spent a year in space?

For the first time, an American Astronaut, Scott Kelly, spent a full year in space. What happens to the human body when it is in space for that long?

1. Without the effect of gravity working on our body, our bones lose minerals. Bone density in space drops over 1% per month (compared to bone loss of the elderly on Earth which is only 1% per year). Even after returning to earth, it would be difficult to return the bone loss at that rate, so there would be a righter risk of osteoporosis-related fractures later in life.
2. There is an increased risk of developing kidney stones in space because of increased excretion of calcium from the bones.
3. The heart weakens and becomes rounder, because it doesn’t have to pump as hard in space.
4. The body loses muscle strength because of the loss of gravity.
5. Fluids shift upwards to the head, and can cause increased pressure on the eyes, resulting in vision problems.
6. People who stay in space develop sleep disorders as their circadian rhythm is thrown off.
7. In space, the body would be exposed to ten times the radiation that occurs on earth. This can increase cancer risk.

One very important factor that will help NASA researchers learn about the changes that occur in space is that Scott Kelly has an identical twin who is also an astronaut.   NASA can study the differences between their two bodies to learn more about the long-term effects of space.