be valuable. Some studies have been done and published by ANARE (by J. A.Wood, D.J.Lugg and colleagues) and by Lawrence Palinkas at the Naval Health Research Center, among others. Although sleep disorders, anxiety, depression, irritability, fatigue, and several other symptoms are common, they very rarely impair function with any significance and are often transient. High levels of individual motivation and careful screening may be responsible for the minimization of symptoms. There is considerable variation in individual behavioral responses, with minimal impairment of group function. The implications of these and future studies are of great importance to long-duration space missions.

Submariners have been confined below the ocean’s surface for periods of up to 3 months or more. Environmental changes include the absence of sunlight (and UV-B radiation), increased carbon dioxide levels (two to six times the normal level) with accompanying mild respiratory acidosis, and dietary restrictions. Dlugos and colleagues (Dlugos et al., 1995) found a decrease in the levels of urinary calcium excretion and increased PTH levels, along with other changes that seemed to protect against the formation of renal calculi. However, they caution that individuals who were known to form renal calculi were rejected from the missions, which may limit the comparability of submarine missions to spaceflight. Further data must be collected to assess the effect of elevated PTH levels on bone resorption, since no clinical effect was noted. There are many other areas in which controlled clinical studies will provide valuable information for space medicine.

Finally, experience in another analog environment, diving in the North Sea, is unique in that it is directed and financed by commercial organizations. Occupational health among divers is of paramount importance, and David Elliott and coworkers are experts on compression and decompression injuries and physiology, as well as immersion problems. The rigorous screening of divers is appropriate for their tasks, and the planning and delivery of medical care have been given high priorities.

The patterns of illness and injury among individuals in these diverse analog environments show considerable similarities, with some variations caused by methods of reporting, the durations of the missions, and the completeness of the medical studies. Roger Billica, chief of NASA’s Medical Operations Branch, has noted that the Antarctic experience bears the closest resemblance to spaceflight, and emphasis will be placed on using data and information from that experience to prepare for flight beyond Earth orbit.

The examples of studies in analog environments noted above provide



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