WASHINGTON -- According to a new study created for NASA the medical risks -- both physical and psychological -- of long treks beyond Earth orbit remain daunting and a far greater challenge than the public has been led to believe.

After 40 years of rocketing humans skyward, information on stresses to the body due to space travel have not been well collected, nor fully analyzed. Today, not enough is known about the dangers of prolonged travel to enable humans to venture into deep space in a safe and sane manner.

However, the new, no-holds-barred study says part of the problem comes from "underreporting" by space travelers about their health woes. Also, there is too much data privacy and confidentiality between astronauts and flight surgeons.

In the report's foreword, Kenneth Shine, President of the Institute of Medicine, the organization that put together the committee, cautions that deep space exploration, such as a journey to Mars, stirs up new questions about the health of expeditionary crews.

"Some of the physiologic effects of shorter periods in space such as loss of bone calcium are likely to continue indefinitely during longer missions," Shine said. Furthermore, psychological and mental health issues -- spurred by stuffing people from diverse social and cultural background into tight quarters and sending them outward from Earth -- will grow increasingly important, he said.

"For prolonged missions, it will not be feasible to return an acutely ill individual to Earth in a timely manner," Shine said. Not only should the report help NASA, but also others concerned about the care of individuals in isolated locations on Earth, he said.

Ball, as panel chair, said the report is a unique, first-of-its-kind National Academies assessment. The committee sought to bring about a "fresh perspective" in looking at the health of space medicine today, he explains in the report's preface.

That outlook, Ball said, led the group to identify two specific areas where NASA falls short.

The first area involves behavioral and cultural understandings, including crew selection and training. Human interactions aboard a spacecraft, isolated in time and space from Earth, "may well be one of the more serious challenges to exploratory missions by humans," the study group found.

The other area is the collection of clinical data on astronauts.

In this arena, a new ethical approach is needed, Ball said. Too much emphasis has been placed on confidentiality of astronaut clinical data. Overly protective policies focused on astronaut privacy and non-disclosure of medical information has resulted in "lost opportunities" to help unravel the intricacies of human physiological adaptations to space.

In addition, the culture of the astronauts, an 'esprit de corps' resting on stoicism and a 'can-do' attitude, "further reinforces the individual's reluctance to report medical information," the report explains.

Astronauts should be thought of as a unique population of research participants, the committee observed. As such, a high priority for NASA is to assure that space crews reside in a safe work environment. Health related data collected in-flight is essential to creating and maintaining that work environment.

Following four decades of human space travel, "a paucity of useful clinical data have been collected and analyzed," the committee reported. "It is unlikely that all effects of microgravity are known, and surprises may yet be in store as humans venture longer and farther into space."