Effects of Microgravity on Astronaut Physiology in Long-Term Space Missions and Proposed Countermeasures

Abstract

The interest in long-term space travel (>6 months) has gained popularity in the space community. This began in the 1970s with multiple short-term missions exploring the Moon and Mars to understand true habitability and early developments of long-term space settlements. With new missions being proposed by major pioneers in aerospace, such as NASA, SpaceX, and JAXA, scientists are concerned with human health, especially the long-term effects. Long-term settlements have been hypothesized to have major short-term and long-term detriments to multiple physiological systems, most notably musculoskeletal, cardiovascular, and neurophysical. This is due to the effects of microgravity; however, more experimentation must be conducted to understand these effects sufficiently. So far, scientists have linked microgravity to decreased osteoblastic differentiation, rapid bone loss, and increased risk of kidney stone formation in the musculoskeletal system. Additionally, the cardiovascular system is impacted by space anemia, which is hypothesized to be reversible but may induce detrimental effects. Finally, microgravity affects the vestibular system significantly, especially spatial recognition. Countermeasures have been proposed to reduce these effects, like inducing artificial gravity, administrating bisphosphonates and other drugs/therapies, and utilizing tactile aids. The long-term effect of microgravity is still an emerging topic of space research, and much more research must be conducted through various programs like the Artificial Gravity Bed Rest Study with the European Space Agency (AGBRESA) to understand long-term results better.