During longer space exploration trips, all of the medical concerns are due to the absence of gravitational force. Crewmembers may develop short-term conditions which are reversible. Those conditions include: vision impairment risks and short-term cardiac atrophy, increase in length, weight loss, vestibular dysfunction etc.
On the other side, the long-term medical condition is loss of bone mineral density (negative calcium balance) and radiation exposure which are irreversible.