Local immunocompetence and salivary cortisol in confinement

Area of Science:

• Space Medicine
• Human Physiology
• Immunology

Background:

• Long-term isolation presents unique physiological challenges.
• Understanding stress and immune responses in confined environments is crucial for astronaut health.
• The EXEMSI project investigated the effects of simulated space isolation.

Purpose of the Study:

• To assess the impact of a 60-day isolation period on salivary cortisol and secretory immunoglobulin A (sIgA) levels.
• To examine individual variations in immune and stress marker responses to confinement.
• To investigate the relationship between isolation, circadian rhythms, and physiological adaptation.

Main Methods:

• Four volunteers were isolated in a space station-like chamber for 60 days.
• Salivary cortisol and sIgA levels were measured twice weekly.
• Measurements were taken before and after a complex decision-making test.
• Analysis included examination of cyclic variations, weekday-weekend differences, and circadian rhythms.

Main Results:

• Secretory IgA secretion rates exhibited distinct cyclic variations and adaptation time lags related to daily schedules.
• Salivary cortisol displayed a circadian rhythm and a significant 12- to 14-day cycle.
• Morning-evening cortisol differences varied, with some subjects showing them only on weekends.
• Subject responsiveness to a decision-making test changed over the isolation period.

Conclusions:

• Sixty days of isolation significantly altered salivary cortisol and sIgA levels and their patterns.
• Individual variability in physiological adaptation to long-term confinement was observed.
• Confinement impacts both the innate immune system and the hypothalamic-pituitary-adrenal axis, affecting cognitive performance.