Peer-review started: March 12, 2019
First decision: July 17, 2019
Revised: September 29, 2019
Accepted: December 13, 2019
Article in press: December 13, 2019
Published online: December 27, 2019
Processing time: 294 Days and 7.3 Hours
Although human hibernation has been introduced as an effective technique in space exploration, there are concerns regarding the intrinsic risks of the approach (i.e., synthetic torpor) and other factors involved in this procedure. Besides concerns about the brain changes and the state of consciousness during hibernation, an "Achilles heel" of the hibernation is the negative impact of torpor on factors such as the number of circulating leukocytes, complement levels, response to lipopolysaccharides, phagocytotic capacity, cytokine production, lymphocyte proliferation, and antibody production. Moreover, increased virulence of bacteria in deep space can significantly increase the risk of infection. The increased infection risk during long-term space missions with the combined effects of radiation and microgravity affect the astronauts’ immune system. With these additional immune system stressors, torpor-induced extra-immunosuppression can be potentially life threatening for astronauts.
Core tip: During long-term manned space missions beyond the protective shield of Earth's atmosphere and magnetic field (e.g., a mission to Mars or a long stay on the Moon), while the combined effect of radiation and microgravity affects the astronauts’ immune system, torpor-induced extra-immunosuppression can be potentially life threatening for astronauts.