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Local immunocompetence and salivary cortisol in confinement
Insights
Long-term isolation affects stress and immune markers. Salivary cortisol and immunoglobulin A levels showed altered patterns and responsiveness during a 60-day space-like confinement, impacting physiological adaptation.
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.
Abstract:
The present study describes the effects of a 60-day isolation period on the salivary levels of cortisol and secretory IgA. The study took place in the context of the EXEMSI project in which four volunteers were isolated in a space station-like chamber in the DLR Institute of Aerospace Medicine in order to examine the effects of long term isolation. Inspection of the individual immunoglobulin A secretion rates revealed different patterns of cyclic variation with respect to the weekday-weekend schedule, and different time lags for the adaptation leading to a plateau for this parameter. The salivary cortisol levels showed a circadian rhythm with high concentrations in the early morning (7:30 am) and lower concentrations in the late evening (11:00 pm). Moreover, in all subjects marked increases of salivary cortisol were observed in a 12- to 14-day cycle. In two subjects the marked morning-evening differences were only visible at the weekends. The salivary cortisol and immunoglobulin A levels were determined twice weekly before and after completion of a complex decision-making test. The results reveal a changed responsiveness in all subjects at different times.