Specifically, the primary a priori hypotheses to be tested were: 1) astronauts are at different risk of total morbidity (defined as rate of incident cases of diseases/disorders, rate of hospitalizations, and average number of hospitalization days per person), than ground-based employees; and 2) astronauts are at different risk of total mortality than ground-based employees. Risk was measured relative to civil service employees located at the Johnson Space Center (JSC) who work and live, at least for a time, in the same geographical area as the astronauts; who participate in the JSC Occupational Medicine Clinic (OMC) Employee Wellness Program by undergoing preventative health examinations; and who have volunteered to participate in the study.
All astronauts selected for the NASA astronaut program were followed as "exposed" subjects from selection through-out the course of the study. Civil service employees who receive routine annual physical examinations at the OMC are selected as comparison subjects using age, sex, and body mass index as selection criteria, and they are followed in the same manner as the astronauts. As new astronauts are selected, matching groups of comparison participants were identified and recruited. The ratio of participants was three comparison subjects for every one astronaut. Morbidity, mortality, physical examination, and laboratory data were collected utilizing medical records routinely collected at the Johnson Space Center, as well as medical consultant reports, hospital discharge summaries, death certificates, and, when available, autopsy reports. The data bases are useful as computerized medical records as well as for research purposes.
The personal medical data included in the data bases of the LSAH are protected by the Privacy Act of 1974 and by the additional Security procedures and Policies of the LSAH and the JSC Clinics. Individual participant data are not included in reports or publications; only group data are presented.