The goal of this data mining effort is to identify if any evidence of this potential risk exists in the NASA astronaut population. Our central hypothesis is that NASA has successfully mitigated this potential threat of subclinical neurologic DCS linked to WMH and neurocognitive deficits in past and present missions but may encounter it in the future. We have based this hypothesis on the fact that NASA has no reported incidents of DCS during operational EVAs (extravehicular activity) and no apparent signs of neurocognitive deficits amongst its astronauts. However, NASA plans on increasing the number of hypobaric exposures of its astronauts by several orders of magnitude in the future. Successful completion of this data mining effort will enable NASA to make an informed decision on the need for proper mission monitoring and occupational surveillance for past, present, and future astronauts.

Aims:

Aim #1: Determine if cumulative hypobaric exposures including EVAs are a risk factor for WMH increase on MRI amongst NASA astronauts during past operations. Hypothesis: NASA's risk-mitigation measures sufficiently minimize the risk of DCS over repeated hypobaric exposures. We will execute a retrospective study on existing MRIs of astronauts' brains compared with those of USAF U-2 pilots, hypobaric technicians, and an age-, health-, and intelligence-matched control population.

Aim #2: Develop new measures to estimate the future risk of DCS for astronauts and missions based on newly revealed data of subclinical neurologic DCS. Hypothesis: NASA is underestimating the risk of subclinical DCS for future astronauts and missions because of the paucity of clinical DCS during past operations. We will estimate the risk of subclinical DCS effects based on the current evidence, the anticipated increase in projected number, time, and frequency of EVAs per astronaut and a prolonged hypobaric exposure based on the ambient environment of future expeditionary space vehicles.

Initial incidence of WMH in astronauts was higher than other subjects groups including military high altitude pilots, military hypobaric chamber technicians, and an advanced degreed control group. This study only reviewed the last available post-flight MRI in a convenience sample of astronauts. Initial results do not indicate that EVA exposure is a primary explanatory variable for the presence of WMH on MRI.

Follow-up work will evaluate the pre-flight MRI and if evidence of an increase in WMH is linked to spaceflight exposure; then future data mining efforts looking for contributory variables will be explored. Also, determination of a functional consequence related to WMH on MRI will be explored.

The goal of this data mining effort is to identify if any evidence of this potential risk exists in the NASA astronaut population. Our central hypothesis is that NASA has successfully mitigated this potential threat of subclinical neurologic DCS linked to WMH and neurocognitive deficits in past and present missions but may encounter it in the future. We have based this hypothesis on the fact that NASA has no reported incidents of DCS during operational EVAs (extravehicular activity) and no apparent signs of neurocognitive deficits amongst its astronauts. However, NASA plans on increasing the number of hypobaric exposures of its astronauts by several orders of magnitude in the future. Successful completion of this data mining effort will enable NASA to make an informed decision on the need for proper mission monitoring and occupational surveillance for past, present, and future astronauts.

Aims:

Aim #1: Determine if cumulative hypobaric exposures including EVAs are a risk factor for WMH increase on MRI amongst NASA astronauts during past operations. Hypothesis: NASA's risk-mitigation measures sufficiently minimize the risk of DCS over repeated hypobaric exposures. We will execute a retrospective study on existing MRIs of astronauts' brains compared with those of USAF U-2 pilots, hypobaric technicians, and an age-, health-, and intelligence-matched control population.

Aim #2: Develop new measures to estimate the future risk of DCS for astronauts and missions based on newly revealed data of subclinical neurologic DCS. Hypothesis: NASA is underestimating the risk of subclinical DCS for future astronauts and missions because of the paucity of clinical DCS during past operations. We will estimate the risk of subclinical DCS effects based on the current evidence, the anticipated increase in projected number, time, and frequency of EVAs per astronaut and a prolonged hypobaric exposure based on the ambient environment of future expeditionary space vehicles.