Dr. Shearer's team is investigating links between the stress of lack of sleep and a weakened immune system. There is therefore evidence to suggest that stress and sleep disorders adversely affect health. In space, sleep cycles are likely to be disturbed. The human biological clock is so carefully tuned that when it is disturbed the body's hormones can become unbalanced. Workloads are great, especially on a long-duration mission, and astronauts will be unlikely to be able to enjoy regular hours.
Stress is a given.
Our hypothesis is that it is highly likely to have a harmful effect on the immune system. This is because there are a number of parallels between groups working in the Antarctic environment and those involved in long duration space flight. People 'wintering' there are almost totally isolated for nine to twelve months of the year, with no possible way of evacuation in case of emergency. The population is a transient one. The lifestyle there must be self-sustaining and people are dependent on technology for survival.