Microbial and fungal contamination contributes to physical stress in space flight: studies in the Euromir-95 mission.

Astronauts are subjected to flight-induced physical and psychic reactions which may be health threatening in the long term. Stress is a basic component of space missions, where astronauts are confined in a reduced volume, live in a hostile environment, have limited contact with the rest of the world and undergo a severe work load. Chronic stress in microgravity stimulates the HPA (hypothalamo-pituitary-adrenal) axis in astronauts with consequent hypercortisolim. Stress also stimulates the autonomic nervous system. Both increased cortisol and adrenergic stimulation suppress the immune function. For these reasons we developed experiments to contemporaneously measure the autonomic, HPA-axis and immune function in space missions. All measures are made with non-invasive methods. Autonomic adaptation is measured by spectral analysis of ECG derived interval, arterial pressure and respiration. HPA-axis function is assessed by measuring cortisol, F-Testosterone and DHEA in saliva. Immune function is monitored by measuring cytokine production and Th1/Th2 balance in saliva. Till now these experiments were performed on the ground. On 1998-99 space experiments will be performed and space technologies will be set up in collaboration with DMR company (Varese), to allow astronauts to measure stress factors directly in space. I.R.C.E.A. research, sponsored by the Italian Space Agency and selected by ESA and NASA, is focused on conditions which influence health in space flight: in particular, stress and microbial contamination. These two conditions are strictly correlated as infections causes stress and stress, by inhibiting the immune system, makes infection easier.