Characterizing the effect of exposure to microgravity on anemia: more space is worse

Abstract

The effects of space travel have renewed importance with space tourism and plans for long-term missions to the moon and Mars. The study of space anemia is limited by the availability of subjects and extreme conditions. An approach using the accumulated data on human space flight may characterize space anemia. A total of 17 336 hemoglobin (Hb) concentration measures from 721 space missions and controls were used to study acute and long-term effects of duration of exposure to space on Hb decrement.Nearly half of astronauts (48%) landing after long duration missions were anemic.Returning to Earth revealed Hb decrements whose magnitude and time to recover were dependent on exposure to space: −0.61 g/dL (4%), −0.82 g/dL (5%) and −1.66 g/dL (11%) of preflight Hb for mean exposure to space of 5.4, 11.5, and 145 days, respectively. Astronauts returning from a mean 5.4 days in space took 24 days to return to preflight Hb while astronauts 11.5 to 145 days in space took 49 days. Negative effects of microgravity on Hb persisted throughout female and male astronautsʼ terrestrial lives (−0.001 and −0.002 mg/dL Hb respectively) for every day spent in space (both P < .05). The negative effect of exposure to space was not overcome by a statistically significant effect of being an astronaut compared to controls.Exposure to space showed a dose-response relationship with acute and chronic Hb decrements. Space anemia contributes to the deconditioning of astronauts returning to Earth, and needs to be considered for space travel to other planets, space tourism and for the care of bedridden patients who present similar changes as astronauts.

Long‐duration spaceflight alters estimated intracranial pressure and cerebral blood velocity

“…These findings can be interpreted as showing that plasma volume reductions are restored faster upon return to Earth than reductions in red blood cell volume, which recover more slowly (Kunz et al 2017). The present results showing decreased haemoglobin concentrations are consistent with these previous results from ISS crews after landing (Smith et al 2005;Kunz et al 2017;Trudel et al 2020). For recent ISS crews, oral fluid loading prior to re-entry and/or intravenous fluid administration after landing have frequently been used to restore the reductions in circulatory volume as a countermeasure against orthostatic intolerance after returning to Earth (Fu et al 2019).…”

“…Kunz et al (2017) clearly reported that red blood cells and haemoglobin concentration increased aboard the ISS, suggesting greater reductions in plasma volume than reductions in red blood cells during spaceflight. However, following a long-duration spaceflight aboard ISS, haemoglobin concentrations significantly decreased below preflight levels (Smith et al 2005;Kunz et al 2017), and the decreases were most apparent 4-8 days after spaceflight at the nadir of haemoglobin concentration (Trudel et al 2020). These findings can be interpreted as showing that plasma volume reductions are restored faster upon return to Earth than reductions in red blood cell volume, which recover more slowly (Kunz et al 2017).…”

“…On the other hand, a previous report on short-duration spaceflight using a very similar experimental setting (Iwasaki et al 2007) did not show increases in MCAv, in contrast to the present results showing significant increases in MCAv in the supine position after spaceflight. This inconsistency could be explained by a dose-response relationship for 'space anaemia' after spaceflight (Trudel et al 2020). Numerous researchers have proposed reductions in both plasma volume and red blood cell volume to a new set point as a result of physiological adaptation during spaceflight (Sawka et al 2000;Diedrich et al 2007).…”

Six degrees head-down tilt bed rest caused low-grade hemolysis: a prospective randomized clinical trial

“…More recently, longer-duration space missions followed erythropoietic adaptation to space after the initial 10 days and reported no anemia onboard the ISS throughout 6-month missions questioning whether space anemia was real or had been resolved with modern space travel 5 . However, epidemiological data from over 5 decades of American and Canadian presence in space confirmed and characterized space anemia 6 .…”

Molecular Pharming to Support Human Life on the Moon, Mars, and Beyond

“…The list of necessary supplies to address persistent exposures of space travel adds up quickly: includ ing countermeasures for increased radiation 3,4 , bone loss 5,6 , kidney stones 7,8 , vision impairment 9 , and adverse behavioral conditions 10 to name a few. The list of supplies begins to look unmanageab le when you add in intermittent, or even unanticipated, exposures such as microbial infection [11][12][13] , and implications of spaceflight-induced genome instability and metabolic changes 14 . As missio n duration increases, the risk of a low probability medical condition is amplified; when an astronaut is on Mars and the closest hospital or medical re-supply is at least 200 days of interplanetary travel away 15 , it is critical that astronauts are prepared for self-sufficiency.…”