Contrapositive logic suggests space radiation not having a strong impact on mortality of US astronauts and Soviet and Russian cosmonauts

Abstract

Space travelers are exposed to unique forms of ionizing radiation that pose potentially serious health hazards. Prior analyses have attempted to quantify excess mortality risk for astronauts exposed to space radiation, but low statistical power has frustrated inferences. If exposure to deep space radiation were causally linked to deaths due to two particular causes, e.g., cancer and cardiovascular disease, then those cause-specific deaths would not be statistically independent. In this case, a Kaplan-Meier survival curve for a specific cause that treats deaths due to competing causes as uninformative censored events would result in biased estimates of survival probabilities. Here we look for evidence of a deleterious effect of historical exposure to space radiation by assessing whether or not there is evidence for such bias in Kaplan-Meier estimates of survival probabilities for cardiovascular disease and cancer. Evidence of such bias may implicate space radiation as a common causal link to these two disease processes. An absence of such evidence would be evidence that no such common causal link to radiation exposure during space travel exists. We found that survival estimates from the Kaplan-Meier curves were largely congruent with those of competing risk methods, suggesting that if ionizing radiation is impacting the risk of death due to cancer and cardiovascular disease, the effect is not dramatic.

Guest Edited Collection: Gravitational biology and space medicine

“…The Guest Edited Collection ‘ Gravitational biology and space medicine ’ includes publications reporting on health concerns for astronauts and cosmonauts 14–16 during space missions, and physiological changes caused by short-term µ g 17 . Several studies investigating the impact of µ g on the behaviour and health of mice on the ISS were published in this Collection 18–23 , in addition to investigations at the cellular level in space 24 and in short-term µ g provided by PF maneuvers 25 .…”

“…Reynolds et al . 16 , investigated 301 astronauts and 117 cosmonauts, demonstrating that space radiation has no strong impact on their mortality. They showed that survival estimates from Kaplan-Meier curves were largely congruent with those of competing risk methods, suggesting that if ionising radiation impacts the risk of death due to cancer and cardiovascular disease, the effect is not dramatic 16 .…”

“…16 , investigated 301 astronauts and 117 cosmonauts, demonstrating that space radiation has no strong impact on their mortality. They showed that survival estimates from Kaplan-Meier curves were largely congruent with those of competing risk methods, suggesting that if ionising radiation impacts the risk of death due to cancer and cardiovascular disease, the effect is not dramatic 16 . However, the authors concluded that future deep space exploration might provide larger doses of space radiation, leading to a different risk profile for future astronauts and cosmonauts; therefore, it is important to continue their surveillance for potential harmful effects of such exposure 16 .…”

The role of cardiovascular CT in occupational health assessment for coronary heart disease: An expert consensus document from the Society of Cardiovascular Computed Tomography (SCCT)

“…In aircrew, despite a consistent finding of lower risk of CVD mortality compared to the general population, the prevalence of CAD in pilots is the same as age-matched controls in the general population, 18,19 and whilst most experienced astronauts are middle aged, and at risk for developing major adverse cardiovascular events, recent contemporary data has revealed similar rates of developing CVD as the general population despite exposure to spaceflight. [20][21][22][23] In the military, like the general population, the most frequent cause of death is CAD, with an increasing trend seen with increasing age. [24][25][26] Whilst recruiting at a younger age, a focus on physical fitness, 27,28 reduced obesity levels [29][30][31] and the early discharge of those with conditions known to predispose to CVD, such as diabetes, 29,31 chronic kidney disease or rheumatoid arthritis, may reduce the burden of CVD, 32,33 a higher proportion of males recruited from lower socioeconomic groups, increased rates of smoking 31,[34][35][36] and a paradoxical increased rate of cardiovascular events due to vigorous exertion may not only negate any benefits, but worsen cardiovascular health in comparison to the comparative normal population.…”

Cancer Incidence and Mortality in the U.S. Astronaut Corps, 1959-2017

“…The database has been used extensively in prior publications concerning astronaut mortality. [5][6][7] Counts of tumors and cancer deaths were obtained from the 2019 issue of the newsletter of the Lifetime Surveillance of Astronaut Health (LSAH) at NASA, with input from the LSAH on speci c tumor and death counts. 8 In comparison to the original source table, 2 cancers (1 melanoma and 1 testicular) were removed from the tumor counts, as they were diagnosed prior to time of selection to the Astronaut Corps.…”