From the Guidelines
Astronauts' prolonged stay in space is associated with several health issues, including Space-Flight Related Neuro Ocular Syndrome (SANS), which is a novel entity consisting of a group of clinical features resulting from exposure to prolonged microgravity. The underlying pathophysiology of SANS is still being debated, but it is a growing concern with the increasing number of civilians traveling to space 1. Some of the key health issues associated with astronauts' prolonged stay in space include:
- Vision problems from fluid shifts, such as SANS
- Bone density loss
- Muscle atrophy
- Cardiovascular deconditioning
- Immune system suppression
- Radiation exposure risks
To counter these effects, astronauts follow comprehensive countermeasure regimens, including:
- Daily exercise using specialized equipment
- Vitamin D supplements to support bone health
- Bisphosphonates like alendronate to reduce bone loss
- Compression garments to maintain muscle tone
- Strict sleep schedules and medications like zolpidem or melatonin to manage sleep disruptions
- Radiation exposure monitoring and sheltering in designated areas during solar events. The most recent study on this topic, published in 2023, highlights the importance of addressing these health issues to ensure the well-being of astronauts during prolonged space missions 1.
From the Research
Health Issues Associated with Prolonged Spaceflight
- Bone loss: Astronauts on prolonged spaceflights may experience bone loss, which can increase the risk of osteoporosis, fractures, and renal stone formation 2, 3.
- Declines in bone mineral density: Spaceflight can cause declines in bone mineral density, particularly in the spine, hip, and pelvis 2, 3.
- Elevated levels of bone resorption markers: Prolonged spaceflight can lead to elevated levels of bone resorption markers, indicating increased bone breakdown 2, 3.
- Urinary excretion of calcium: Spaceflight can cause increased urinary excretion of calcium, which can contribute to bone loss and kidney stone formation 2.
- Trabecular bone loss: Resistive exercise, such as that provided by the Advanced Resistive Exercise Device (ARED), may not prevent declines in trabecular bone density 3.
- Cortical bone loss: However, resistive exercise can help prevent declines in cortical bone density and estimates of hip strength 3.
Factors Influencing Bone Loss
- Mission duration: Longer mission durations are associated with greater bone loss 4.
- Pre-flight exercise history: Astronauts with higher levels of pre-flight exercise may experience less bone loss during spaceflight 4.
- In-flight exercise: Increased in-flight exercise, particularly lower body resistance training, can help preserve bone strength and density 4.
- Biomarkers of bone turnover: Elevated pre-flight levels of biomarkers of bone turnover may predict greater bone loss during spaceflight 4.
Other Health Concerns
- Behavioral health and performance factors: Prolonged spaceflight can also affect astronauts' behavioral health and performance, including sleep and circadian factors, behavioral health factors, psychological adaptation factors, and human-to-system interface factors 5.
- Medical operations: The development of progressively Earth-independent medical operations is necessary to support crews on long-duration missions and reduce overall mission risk 6.