Space Adaptation Syndrome

Space adaptation syndrome, also known as astronaut syndrome, refers to the set of physical symptoms experienced during space travel due to the absence of gravity (microgravity). Gravity plays a fundamental role in the human spatial orientation system, so any changes in gravitational forces affect the body until it can adapt.

Approximately half of astronauts in orbit experience this syndrome during the first few days of the journey and in the days following their return to Earth.

Symptoms

The most common symptoms of space adaptation syndrome include:

• Dizziness.
• Disorientation.
• Vertigo.
• Headache.
• Cold sweats.
• Fatigue.
• Nausea.
• Vomiting.

Causes

The primary cause of space adaptation syndrome is the sensory conflict between the vestibular system and the visual system due to microgravity. In orbit, signals from the vestibular system, located in the inner ear and responsible for balance and spatial control, no longer provide direct information about gravitational acceleration. This affects the brain areas responsible for integrating sensory information from vision, proprioception, and vestibular input for spatial orientation.

In space, the environment visually appears to be in motion (as objects and people "float"), but the vestibular system does not detect any movement in the body. This incongruity leads to disorientation and vertigo. It is the opposite process of motion sickness, the kinetic dizziness experienced when traveling in any vehicle on Earth's surface.

Additionally, fluid shifts induced by microgravity are also believed to contribute to the syndrome. In orbit, blood and lymph move toward the upper body due to the absence of hydrostatic pressure. This shift affects the balance of vestibular lymphatic pressure and may cause nausea and vomiting.

Risk Factors

Astronauts are at higher risk of developing space adaptation syndrome based on the following factors:

• Age: Sensitivity to motion sickness decreases with age.
• Sex: Women have lower tolerance.
• Genetics: Susceptibility to motion sickness may be hereditary.
• Lack of experience in orbit.
• Sleep deprivation.

Complications

In some cases, space adaptation syndrome can lead to severe cognitive and sensorimotor impairment, including temporary loss of consciousness, which can be dangerous in emergency situations, as the astronaut may be unable to react normally.

Additionally, microgravity can cause other serious issues in the body, such as movement difficulties due to muscle mass loss or kidney stones resulting from decreased bone mineral density and dehydration. Short- and long-term effects on the cardiovascular system may also occur due to pressure changes.

Prevention

To prevent the symptoms of the syndrome, astronauts undergo tests and training to measure and acclimate to gravitational effects:

• Centrifuge chambers: Centrifugal force creates altered gravitational forces.
• Parabolic flights: These trigger short periods of hypergravity, hypogravity, and microgravity through acceleration and free-fall phases.
• Neutral buoyancy pools: These provide an experience similar to the low gravity of space.
• Rotating environments: Rotating rooms or chairs alter the visual and vestibular information interpreted by the body and brain.

What Type of Doctor Treats Space Adaptation Syndrome?

Space adaptation syndrome is studied in the aerospace medicine unit.