Considering in further assessing the adverse effects of space-travel

Considering the importance that space-travel will hold as
organizing governing and private entities continue to push spaceflight to the
global forefront, we must be wary in further assessing the adverse effects of
space-travel and the harsh space environment on human health in orbit travel
and beyond. Preservation of optimal health remains an important priority as an
important perquisite in expanding programs and protocols concerning
spaceflight. Further understanding how and why these adverse effects occur helps
researchers as they continue to develop countermeasures and alternative methods
to lessen these effects from the conditions of space.  If these adverse effects can be limited to
safer, more sustainable levels through certain countermeasures, then further
growth and expansion of space-travel can be ensured along with subsequent
contribution to traditional medical/physiological research on Earth.

            Space
travel and the conditions of the space environment impact human health in ways
that disrupt normal physiological processes and bodily conditions. Feasible functioning
of the human body serves as a testament to the more favorable gravitational
setting on Earth. As space-travel becomes more frequent, prolonged exposure to
microgravity from “weightlessness” becomes an area of focus with how it affects
the human body. Microgravity is referred to the state where objects appear to
be “weightless” due to free-fall in orbital travel. Though in free-fall,
objects travel in orbit fast and well enough to appear “weightless” all in the
while floating with microgravity coming into effect as gets closer to nearing
zero g. In these environments where microgravity pertains, gravity no longer
acts as a significant force acting upon the human body and normal physiological
functioning. Exposure to both real and simulated microgravity conditions
negatively impacts ophthalmic, musculoskeletal, and cardiovascular health. Bone
and muscle strength decline as gravity no longer acts as a strong bearer/loader
of force in microgravity conditions. Blood flow and pressure are dependent on gravity’s
effects as such changes spur subsequent physiological/cardiovascular imbalances
leading to blood loss and atrophy. Biological changes induced by space-travel also
parallels that of the traditional aging process. Space travel even affects the
immune system and its responsiveness/function.1

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Vision impairment is one of the most
reported side effects seen in space travel. Frequently observed by those coming
back to Earth from prolonged spaceflight, vision impairment is attributed to
changes in intracranial pressure (ICP).2
On Earth, intracranial pressures differ on position whether an individual is
upright or supine (lying down). Daytime ICP is mostly lower as we are upright
and active during most of the day. Intracranial pressure increases during
nighttime in supine position, though occurring for a lesser time than daytime,
upright ICP. Considering how lower ICP is more favorable for eye health, the
ability for our body to regulate and systematically balance ICP between
nighttime and daytime makes current Earth conditions ideal from an ICP
standpoint. In microgravity during space-travel, ICP is still higher than
normal upright ICP with levels closely resembling that of higher pressure
normal supine levels. Though ICP is reduced by a bit, it will remain higher
than normal, upright ICP while closely resembling high levels seen in supine
ICP. The main caveat is the relative lack of systematic regulation and
balancing, as seen on Earth, in space.3
Prolonged exposure leads to gradual but long-term buildup of ICP. Along with
these unfavorable changes in ICP, there also exists the problem with gradual
cerebrospinal fluid and other bodily fluids from the lower body to the upper
body. Buildup of fluid pressure along with gradual ICP pose as risks to optical
remodeling of the eye. Due to prolonged exposure, those coming back to Earth
from orbit are more prone to vision impairment such as hyperopia and other permanent
damages.4
Though other factors come in play, the buildup of pressure in upper body at the
head and fluids shifts in microgravity conditions can be attributed to
increased risk for vision impairment.

1 Williams,
David, et al. “Acclimation during Space Flight: Effects on Human Physiology.”
CMAJ: Canadian

Medical
Association Journal, vol. 180, no. 13, 2009, pp. 1317–23.

2 Lawley,
Justin S., et al. “Effect of Gravity and Microgravity on Intracranial
Pressure.” Journal of

Physiology,
vol. 595, no. 6, 2017, pp. 2115–2127.

3Ibid

4 Aubert,
André E, et al. “Towards Human Exploration of Space: the THESEUS Review Series
on

Cardiovascular,
Respiratory, and Renal Research Priorities.” NPJ Microgravity, vol. 2, 2016, p.
16031.