A review of 79 U.S. space missions involving 219 person-flights lasting 2 to 17 days each (Putcha et al., 1999) reported that the most common conditions experienced were space motion sickness (SMS), nasal congestion, and sleep disorders. None of these medical conditions have required the mission to end, have been life threatening, or have required intensive medical treatment; they are bothersome but are not medical emergencies. Exploration-class missions, however, because of their lengths of as many as 3 years beyond Earth orbit, raise in NASA’s current judgment the probability of a major medical event, a condition requiring intervention by a medical practitioner, during the mission (Billica, 2000).
A study of 175 astronauts from 1959 to 1991 reported 20 deaths (19 males and 1 female), mostly unrelated to spaceflight because of high rates of automobile and aircraft accidents and accidental deaths on the Apollo 1 and the Challenger spacecrafts. The small numbers of participants and the premature deaths from injuries may well mask the morbidity and mortality figures from other disorders related to spaceflight, such as cancer, if the participants live long enough (Peterson et al., 1993). Related disorders such as the development of cancer and cardiovascular, arthritic, and other conditions may increase in frequency as the duration of space travel and the ages of astronauts increase, just as they would had the same individuals remained on Earth.
The risks of medical events increase with the lengths of missions (Billica et al., 1996). A survey of the perception of risk from spaceflight was returned by 65 medical professionals and showed that medical events with the highest perceived likelihood of occurrence had the least effect on the mission or the crew, but those with the greatest impact on the mission or crew were least likely to occur (Billica et al., 1996). Skin disorders (irritation from fiberglass, contact dermatitis, rashes, and furuncles) were thought to be the most common, followed by respiratory and digestive disorders.
NASA reported that 1,867 medical events occurred from 1981 to 1998 on space shuttle flights STS-1 to STS-89 (Billica, 2000). Among the population of 508 individuals on those flights, 498 reported a medical event or symptom other than SMS. The events, derived from a histogram presented to the committee (Billica, 2000), were ill-defined symptoms (n=788), respiratory events (n=83), symptoms related to nervous system or sensory organs (n=318), digestive disorders (n=163), symptoms related to skin or