Increased core body temperature in astronauts during long-duration space missions

Abstract

Humans’ core body temperature (CBT) is strictly controlled within a narrow range. Various studies dealt with the impact of physical activity, clothing, and environmental factors on CBT regulation under terrestrial conditions. However, the effects of weightlessness on human thermoregulation are not well understood. Specifically, studies, investigating the effects of long-duration spaceflight on CBT at rest and during exercise are clearly lacking. We here show that during exercise CBT rises higher and faster in space than on Earth. Moreover, we observed for the first time a sustained increased astronauts’ CBT also under resting conditions. This increase of about 1 °C developed gradually over 2.5 months and was associated with augmented concentrations of interleukin-1 receptor antagonist, a key anti-inflammatory protein. Since even minor increases in CBT can impair physical and cognitive performance, both findings have a considerable impact on astronauts’ health and well-being during future long-term spaceflights. Moreover, our findings also pinpoint crucial physiological challenges for spacefaring civilizations, and raise questions about the assumption of a thermoregulatory set point in humans, and our evolutionary ability to adapt to climate changes on Earth.

Immune System Dysregulation During Spaceflight: Potential Countermeasures for Deep Space Exploration Missions

“…This includes appropriate living conditions, social interactions and communication (within the group, with mission control, and relatives on Earth), habitat design and privacy, adequate nutrition, exercise, sleep, air quality, and circulation. Also, adjustments of adequate calorie intake in light of higher body core temperatures ( 106 ) and avoidance of permanently over-activated sympathetic activities (with concomitant release of stress-permissive hormones) need to be considered as an integrated element of countermeasure design.…”

Adaptation of the cardiovascular system to weightlessness: Surprises, paradoxes and implications for deep space missions

“…Another possible mechanism for the systemic vasodilation in space could reside in the reported increase in core body temperature on the ISS by Stahn et al These authors observed by an indirect method combining a skin surface temperature sensor with a heat flux detector on the forehead that core body temperature increased by one degree Celsius on the ISS (N = 11). The mechanism for this could be the weightlessness induced lack of air convection around the body diminishing heat loss, increasing core body temperature and inducing peripheral vasodilation.…”

“…56,73 The hypothesis can still be correct, however, concerning long duration flights of the following reasons: (a) In the Shuttle studies, measurements inflight 56 were compared to in the acute supine ground position so had the upright seated posture been used instead, the conclusions might have been different; (b) the Shuttle flights were considerably shorter than on the Space Station, and the fluid shift as indicated by, for example, the increase in stroke volume and CO are more pronounced during longer missions. 28,33 Another possible mechanism for the systemic vasodilation in space could reside in the reported increase in core body temperature on the ISS by Stahn et al 74 These authors observed by an indirect method combining a skin surface temperature sensor with a heat flux detector on the forehead that core body temperature increased by one degree Celsius on the ISS (N = 11). The mechanism for this could be the weightlessness induced lack of air convection around the body diminishing heat loss, increasing core body temperature and inducing peripheral vasodilation.…”

“…The mechanism for this could be the weightlessness induced lack of air convection around the body diminishing heat loss, increasing core body temperature and inducing peripheral vasodilation. Good evidence for this is also that the increase in core body temperature gradually took place over the initial months in space, 74 which could explain why the peripheral vasodilation was less-though still present-during the shorter shuttle flights for only a few weeks. 28,33 This hypothetical mechanism is illustrated in Figure 4 together with the other possibilities for inducing systemic vasodilation.…”

Rules Regulating the Change in Physiological Parameters of Rats Under Simulated Microgravity and Different Ambient Temperatures

“…The distribution of body fluid in the head [7][8][9]causes body temperature to decrease in the lower body and increase in upper body, resulting in muscle atrophy because of a decrease in heat dissipation [10][11][12], the deterioration of cardiovascular function [13][14][15][16][17][18][19][20] and the weakening of metabolism. Recent research [26] has also found that the core temperature of the human body can rise by 1°C after long periods in space. These effects are likely to result in changes in thermal comfort requirements of the human body.…”