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Review of Nasa’s Longitudinal Study of Astronaut Health 1 Introduction The career of an explorer is risky, and it is chosen by individuals who acknowledge and accept risks beyond those of ordinary daily living. As the disintegration of the space shuttle Columbia upon reentry into the earth’s atmosphere in February 2003 so vividly demonstrated, space travel has unique risks. In addition to the tremendous engineering challenges entailed in getting space travelers launched and returned safely, biomedical information collected by the National Aeronautics and Space Administration (NASA) and the Soviet and Russian space programs has revealed that living in space can produce profound physiological and clinical changes. These changes include the loss of calcium and other minerals from bone, decrease in skeletal muscle mass, decreased or altered absorption of nutrients in the gastrointestinal tract, disturbed fine motor control, increased risks of renal calculi, anemia, and depressed immune system function (Nicogossian et al, 1993; IOM, 2001c). It is now clear that humans can survive and perform acceptably in space for periods of as long as a year despite these changes and that most but not all of the changes are reversible upon return to earth. Much less is known about the potential longterm effects of space flight that are not apparent in the inflight and immediate postflight medical data collected to date, nor is much known about the overall risks of being an astronaut. NASA physicians began contemplating a longitudinal study as early as the late 1970s. In 1980, they convened a panel of eminent epidemiologists to help design a protocol for retrospectively examining basic physiological data from the relatively small number of astronauts who had flown in space by then and comparing those data with similar data from a group of ground-based employees selected retrospectively to match the living astronauts. However, the current prospective study, the Longitudinal Study of Astronaut Health (LSAH), was not approved by the Human Research Policy and Procedures Committee of the Johnson Space Center (JSC) until 1992. Ten years later, NASA’s Chief Health and Medical Officer asked the Institute of Medicine (IOM) for help in assessing the study and making any necessary midcourse corrections.
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Review of Nasa’s Longitudinal Study of Astronaut Health ROLE OF THE INSTITUTE OF MEDICINE A prior IOM report entitled Safe Passage (IOM, 2001c) is recommended as background reading for this study. Despite the fact that it focused on the immediate dangers to the health and safety of astronauts aboard a future mission to Mars, it examined many issues of relevance to the present study, including the role of the astronauts as research subjects and the need for a comprehensive health care system for astronauts. Presently, the IOM, through activities including studies and workshops undertaken at the National Academies under the auspices of its standing Committee on Aerospace Medicine and Medicine in Extreme Environments (CAMMEE), provides NASA’s Chief Health and Medical Officer independent technical advice relevant to aerospace medicine, including medical care of space travelers. A May 2001 CAMMEE meeting included a presentation by scientific staff from the JSC on the LSAH that stimulated considerable discussion and a request by the CAMMEE for additional information at a future meeting. In early fall of the same year, NASA’s Chief Health and Medical Officer wrote a letter to the IOM project officer that described some tentative findings from a recent analysis of the LSAH database by JSC scientists and requested that CAMMEE examine the LSAH and make appropriate medical, scientific, and administrative recommendations for improving the study, as well as recommendations relative to the data trends identified to date. CAMMEE in turn organized the present Committee on the Longitudinal Study of Astronaut Health (CLSAH), which convened for the first time in conjunction with the January 2003 meeting of CAMMEE. NASA had performed some further analysis of the LSAH database in the interim, and after presentation of those analyses, CLSAH’s task was revised and expanded to yield the following charge to the committee: An ad hoc subcommittee formed under the auspices of the IOM Committee on Aerospace Medicine and Medicine in Extreme Environments will examine NASA’s Longitudinal Study of Astronaut Health (LSAH) and make appropriate medical, scientific, and administrative recommendations for improving the study, as well as recommendations relative to the data trends identified to date, inclusion of astronauts from NASA’s international partners, appropriate follow-up of findings, and medical care of current and former astronauts, mission specialists, and other space travelers. In so doing the committee will address the potential relevance of lessons learned from historical exposures such as agent orange, radiation among veterans, and industrial beryllium
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Review of Nasa’s Longitudinal Study of Astronaut Health to the configuration of the LSAH with regard to its usefulness in identifying health risks. GOALS AND DESIGN OF THE CURRENT LSAH According to the most recent published description of the LSAH, the primary aim of the LSAH is: to investigate and describe the incidence of acute and chronic morbidity and mortality of astronauts and to determine whether the unique occupational exposures encountered by astronauts are associated with increased risks of morbidity or mortality. Specifically, the primary a priori hypotheses being tested are: Astronauts are at different risk of total and cause-specific mortality than are ground-based employees; and Astronauts are at different risk of total and specific morbidity than are ground-based employees (Hamm et al, 2000). Study Participants The primary focus of the study is the group of men and women who have been selected as NASA astronauts since the space program began in 1959. This includes both pilots and mission specialists, who have been career astronauts, but not the 27 American payload specialists who generally are scientists or engineers who fly only a single mission and return to their preflight career immediately afterward (five have flown on two missions, and one on three missions). All active astronauts participate in the study. Astronauts who have retired or otherwise left NASA are invited to continue in the study, and their participation rate is high but not close to universal (the rate of return to JSC for annual exams varied from 61 percent to 88 percent over the nine years between 1993 and 2001). All the ex-astronauts are still “in the study,” although some subset of them misses their exams each year. It is the opinion of the LSAH staff that the same individuals generally return every year. The study also collects health and medical data from a non-astronaut comparison group of JSC employees. The astronauts are a highly screened group selected for specific expertise, education, and personal traits. They must also meet stringent medical standards (that were not written down until 1977 and continue to evolve), presenting a considerable challenge in constructing a useful comparison group. Military pilots, astronaut applicants who passed the medical examination criteria but were not selected, scientists who wintered over in Antarctica, and other populations were considered as possible comparison groups.
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Review of Nasa’s Longitudinal Study of Astronaut Health However, after careful review, it was determined that JSC civil service employees best met the need for a comparison population for this study. JSC employees have similar general ground-based occupational and background environmental exposures as do the astronauts and receive routine physical examinations in the same clinic system that conducts the physical examinations for the astronauts. Although separate staffs of physicians and nurses serve the two groups, the same technicians examine both groups using the same equipment and laboratories. The number of astronauts selected is determined by the needs of the space program; so the number of comparison participants was selected to provide the best combination of statistical power and efficient use of resources. This was determined to be three comparison participants for every astronaut. After each class of astronauts is selected, gender specific means and standard deviations are calculated for age and body mass index (BMI). Male and female employees who have received a physical examination at the Occupational Health Clinic within the previous three years are then identified as potential comparison participants if their age and BMI both fall within two standard deviations of the astronaut means by gender. Individuals are randomly selected from this group and asked to participate in the study. No monetary incentives are offered for participation, and the informed consent process includes statements assuring participants that there would be no adverse consequences for declining to participate or for withdrawing from the study at any time. Selection of comparison participants is now done in the same year that their matching astronaut class is selected, but comparison participants to match astronauts selected prior to the start of the LSAH in 1992 were necessarily selected retrospectively. The first astronaut class, selected in 1959, did not train at JSC, and civilian employees at JSC were too few for a 3:1 match until 1967, so comparison participants for the astronauts selected between 1959 and 1967 were selected from JSC employees of 1967. After 1967, employee records for the year of each astronaut class were used to select comparison participants. In January 2003 the astronaut group totaled 312 and the comparison group 928. Medical Data Collected The primary data for the LSAH are obtained from medical records maintained at the JSC clinics. Annual health evaluations are required of active astronauts and are offered to inactive astronauts. These evaluations consist of a medical history, physical examination, laboratory tests, medical images, and other diagnostic tests. All other JSC employees were offered similar evaluations annually prior to 1994, but now they are offered to them only every three years.
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Review of Nasa’s Longitudinal Study of Astronaut Health Non-astronaut employees who are participating in this study are offered evaluations every other year. Details of these evaluations, which are referred to as “physical exams” in the remainder of the report, are contained below in Table 1-1. Reports and documentation of interim medical care are obtained as part of the evaluation in order to document relevant morbidity information on the examination form. Other study data are obtained from interim visits to the JSC clinics for sick calls, reports from consultants and private physicians, and hospital discharge reports (Hamm et al., 2000; Wear, 2003). Additional data are obtained for astronauts from preflight and postflight physical examinations, medical debriefings following flights, inflight experimental data, and reports of inflight medical events. A questionnaire designed to capture lifestyle factors and health risk data was developed and first mailed to all LSAH study participants in 1994. This questionnaire is now mailed to all new participants when they enter the study. Follow-up questionnaires are mailed to each participant every two years to capture changes and new information. In addition, in 1998, usual nutrient intake was assessed with a mailed food frequency questionnaire (Hamm et al., 2000). Mortality and cause of death are confirmed by death certificate. Biannual searches are done for death certificates of those participants who miss a scheduled examination and cannot be contacted by mail or telephone. Copies of autopsy reports and hospital death summaries to support death certificate data are obtained whenever they are available (Wear, 2003). The actual variables collected and the frequency at which they are collected have changed since the study began, primarily as a result of budgetary constraints. Table 1 shows the measures in the database and the collection schedules for both the astronaut and comparison groups as of January 2003. Appendix B provides a fuller description of each of the measures in the table.
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Review of Nasa’s Longitudinal Study of Astronaut Health TABLE 1-1 Physical and Health Measures Collection Schedule - 2003 LSAH Measures Astronauts Comparisons Notes Physical exam Annually Every 2 years Dental exam Annually, but for active duty only Never Visual acuity Annually Every 2 years Color vision Annually Every 2 years Depth perception Annually Every 2 years Heterophorias Annually Every 2 years Intraocular pressure Annually Every 2 years Audiometry Annually Every 2 years Electrocardiogram (ECG) Annually Every 2 years Pulmonary function by standard spirometry Annually Every 2 years DEXA scan* Every 3 years Never Exercise tolerance test (85% max) Age-specific intervals (US Preventive Services Task Force Guidelines) Age-specific intervals (US Preventive Services Task Force Guidelines) 51+ = annually Comparisons every 2 years Colonoscopy Age 40,50,60,70,80 Age 40,50,60,70,80 Proctosigmoidoscopy Age 45,55,65,75 Age 45,55,65,75 Mammogram Age-specific intervals (US Preventive Services Task Force Guidelines) Age-specific intervals (US Preventive Services Task Force Guidelines) 50+ = annually. Comparisons every 2 years Pelvic exam Annually Every 2 years Pap smear Annually Every 2 years Hematology Annually Annually Lipid profile Annually Annually Urinalysis Annually Annually Chemistry panel Annually Annually Prostate specific antigen Annually after age 40 Annually after age 40 Immunoglobin panel Annually Every 4 years Serology Annually Every 4 years Serum protein panel Annually Every 4 years Self-reported medical history Annually Annually
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Review of Nasa’s Longitudinal Study of Astronaut Health Measures Astronauts Comparisons Notes Medical records from JSC clinics, private physicians, and hospitals Annually, as follow-up to physical exam Every 2 years, as follow-up to physical exam Lifestyle questionnaire Every 2 years Every 2 years Death records Upon notification of death by any source, information I independently verified. Upon notification of death by any source, information is independently verified. Stimulus for professional search is missed exam and no reply to calls or letter Postflight medical debrief Postflight Not applicable * DEXA: dual energy x-ray absorptiometry. SOURCE: Wear, 2003. DATA ACCESS POLICY A detailed protocol describing the policies and procedures involved in accessing the LSAH data has been elaborated and published as Section 6 of The LSAH Manual of Procedures. The following information from that document provides an overview of the procedures in place. The purpose of the LSAH Executive Committee is to ensure that data quality is maintained, the variables are interpreted consistently, there are no redundant projects, and the confidentiality of the participants’ medical data is maintained. To meet its objectives, the Executive Committee reviews and approves all requests for LSAH data before releasing any data from the study database reviews and approves any presentation or publication of the data maintains a permanent file of all requests and the subsequent actions regarding each request The Executive Committee consists of the NASA LSAH Technical Monitor Chief, Flight Medicine Clinic
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Review of Nasa’s Longitudinal Study of Astronaut Health Chief, Medical Operations Branch Assistant to the Director, Space Medicine Assistant to the Director for Biomedical Research and Countermeasures Section Supervisor, Epidemiology Extramural requests for data must receive initial merit and funding approval via the National Space Biomedicine Research Institute (NSBRI) or a NASA Research Announcement (NRA) before they are submitted to the LSAH Executive Committee. If an extramural investigator requests extensive data retrieval and analyses, the Executive Committee may require that the investigator provide the necessary funding to support this work. Intramural data requests are categorized into those for research, clinical care, or operational purposes. Research questions may be submitted by JSC civil servants in the Space Life Sciences Directorate. Contractors, residents, and postdoctoral students and fellows must obtain a civil servant sponsor before submitting their data requests to the Executive Committee. These requests must obtain approval through an independent peer review process before being submitted to the LSAH Executive Committee. Until this process is officially in place, the LSAH Executive Committee will serve this function. Clinical care questions focus on direct patient care and are submitted by JSC Flight Surgeons. These data requests are submitted to the NASA Technical Monitor or the Epidemiology Section Supervisor. Approval by the Executive Committee is not required because the purpose is to support clinical care of individual patients. However, if the Flight Surgeon later wishes to publish or present the results, a study protocol must be developed and submitted to the Executive Committee for review and approval. Data requests for operational or management purposes do not require Executive Committee approval, but results later determined to be publishable require a protocol before they are submitted to the Executive Committee for review and approval.
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