Epidemiological analysis of cosmonaut mortality: 1960–2023

Introduction. Cohort analytical epidemiological studies of cosmonauts’ health have a number of specific features. The estimates of long-term health outcomes in this occupational group can only be refined provided that the observation period of the Soviet and Russian cosmonaut cohort, originally established in 2013, be extended and regularly updated with emerging data.

Objective. Analysis of changes in the main mortality indicators of Soviet and Russian cosmonauts over the cohort observation period extended by five years until 2023.

Materials and methods. Using prospective observation studies over the historically formed cohort of male Soviet and Russian cosmonauts in 1960–2023, data update was implemented. Encoded and anonymized personal data of cosmonauts underwent processing and analysis. Using the standardized mortality ratio (SMR) with a 95% confidence interval (95% CI), mortality risk among cosmonauts was assessed. The total number of participants as of the cohort closure date (31.12.2023) was 270 cosmonauts, divided into two groups based on the presence of spaceflight (SF) experience. Group 1 comprised 127 cosmonauts (47.0%), who undertook at least one SF. Group 2 comprised 143 cosmonauts (53.0%) without SF experience (internal control). The male population of Russia served as the external control group. Cause-of-death analysis was conducted according to ICD-10. Additionally, information on the initial education of cosmonauts as a factor significantly influencing life trajectory was collected. Statistical processing was carried out using the MS and Stata 14 software packages.

Results. Extending the observation period contributed to an increased accuracy of death risk metrics by narrowing the 95% confidence intervals. The all-cause mortality risk among cosmonauts with SF experience was found to be reliably lower compared to both the male population of Russia (SMR = 0.37; 95% CI 0.27–0.50) and cosmonauts without SF experience (SMR = 0.73; 95% CI 0.53–0.98). No statistically significant decrease in cancer-related death risk was observed among cosmonauts with SF experience compared to the general population (SMR = 0.62, 95% CI 0.32–1.09). A correlation was found between the initial education of cosmonauts and mean age at death. Thus, the mean age of death for cosmonauts with military specialization and SF experience was 68.1 years, compared to 60.3 years (p = 0.015) for those without SF experience.

Conclusions. Oncological vigilance in cosmonauts with SF experience is generally higher than in both control groups, despite their unequivocally better health status. Further refinement of the data obtained can only be achieved by extending the observation period, considering the career-long duration of space stay in relation to the health status of cosmonauts. Individual-related factors affecting the health of cosmonauts without SF experience were identified. The link between professional education and the mean age at death underscores the need for developing individual preventive measures for this group and longer post-career health monitoring.

1. Grimes DA, Schulz KF. Cohort studies: marching towards outcomes. Lancet. 2002;359(9303):341–5. https://doi.org/10.1016/s0140-6736(02)07500-1

2. Kholmatova KK, Kharkova OA, Grjibovski AM. Cohort studies in medicine and public health. Human Ecology. 2016;4:56–64 (In Russ.). https://doi.org/10.33396/1728-0869-2016-4-56-64

3. Lebedeva MA, Medvedeva YuS, Baranov MV, Arutyunyan AV, Zolotov NN, Karganov NN. Delayed effects of simulated space flight factors. Pathogenesis. 2021;19(1):37–49 (In Russ.). https://doi.org/10.25557/2310-0435.2021.01.37-49

4. Grigoriev AI, Egorov AD, Potapov AN. Some Medical Problems of the Manned Martian Expedition. Aerospace and Environmental Medicine. 2000;34(3):6–12 (In Russ.).

5. Ushakov IB, Voronkov YuI, Bukhtiyarov IV, Tikhonova GI, Gorchakova TYu. Retrospective health assessment of cosmonauts after participation in space flights. Aerospace and Environmental Medicine. 2016; 50(2):14–20 (In Russ.). https://doi.org/10.21687/0233-528X-2016-50-2-14-20

6. Reynolds RJ, Day SM. The mortality of space explorers. Into Space — A Journey of How Humans Adapt and Live in Microgravity. Ed. by Russomano T, Rehnberg L. London: IntechOpen. 2018:253–85. https://doi.org/10.5772/intechopen.73603

7. Reynolds R, Little MP, Day S, Charvat J, Blattnig S, Huff J, et al. Cancer incidence and mortality in the USA Astronaut Corps, 1959–2017. Occupational and Environmental Medicine. 2021;78(12):869–75. https://doi.org/10.1136/oemed-2020-107143

8. Reynolds RJ, Day SM. Mortality Among International Astronauts. Aerospace Medicine and Human Perform. 2019;90(7):647–51. https://doi.org/10.3357/amhp.5369.2019

9. Betts KV, Fateev IV. Mortality of Russian cosmonauts, 1960–2018. Russian Journal of Occupational Health and Industrial Ecology. 2020;60(11):730–3 (In Russ.). https://doi.org/10.31089/1026-9428-2020-60-11-730-733

10. Chowdhury R, Shah D, Payal AR. Healthy Worker Effect Phenomenon: Revisited with Emphasis on Statistical Methods — A Review. Indian Journal of Occupational and Environmental Medicine. 2017;21(1):2–8. https://doi.org/10.4103/ijoem.ijoem_53_16

11. Andreev EM, Zhdanov DA, Yasilionis D. Confidence estimation of demographic coefficients on the example of mortality rates. Demographics Review. 2015;2(1):24–55 (In Russ.). EDN: VOFMJX

12. Kojiro K. The Healthy Worker Effect in a Long-term Follow-up Population. Japanese Journal of Cancer Clinics. 1999;45(12):1307–10.

13. Fornalski KW, Dobrzynґski L. The healthy worker effect and nuclear industry workers. Dose-Response: An International Journal. 2010;8(2):125–47. https://doi.org/10.2203/dose-response.09-019.fornalski

14. Monson RR. Observations on the healthy worker effect. Journal of Occupational and Environmental Medicine. 1986;28(6):425–33. https://doi.org/10.1097/00043764-198606000-00009

15. Chowdhury R, Shah D, Payal AR. Healthy Worker Effect Phenomenon: Revisited with Emphasis on Statistical Methods — A Review. Indian Journal of Occupational and Environmental Medicine. 2017;21(1):2–8. https://doi.org/10.4103/ijoem.ijoem_53_16

16. Voronkov YuI, Kuzmin MP, Krylova VYu, Krivitsina ZA, Smirnov OA, Tizul AYa, et al. Results of long-term observation of the health of cosmonauts. Aerospace and Environmental Medicine. 2002;36(1):41–4 (In Russ.). EDN: RVZHQD

17. Shafirkin AV. Life expectancy of cosmonauts of the USSR (Russia) and astronauts of the United States and health risks under the influence of various stressors on Earth and in space. Aerospace and Environmental Medicine. 2019;53(7):5–18 (In Russ.). https://doi.org/10.21687/0233-528X-2019-53-7-5-18

18. Berezina TN, Mansurov EI. The influence of stressogenic factors on the life expectancy of cosmonauts. Questions of Psychology. 2015;3:73–83 (In Russ.). EDN: VMGQVD

19. Vancheri F, Longo G, Vancheri E, Henein MY. Mental Stress and Cardiovascular Health — Part I. Journal of Clinical Medicine. 2022;11(12):33–53. https://doi.org/10.3390/jcm11123353

20. Kivimäki M, Pentti J, Ferrie JE, Batty GD, Nyberg ST, Jokela M, et al. Work stress and risk of death in men and women with and without cardiometabolic disease: a multicohort study. Lancet Diabetes and Endocrinology. 2018;6(9):705–13. https://doi.org/10.1016/s2213-8587(18)30140-2

21. Akulov OY. Professional mobility of a military specialist and factors of its formation. Bulletin of the Voronezh State Technical University. 2014;10(3–2):85–90 (In Russ.). EDN: SGITDZ

22. Shcherbakova EA. Personal characteristics of a high-class military pilot. Bulletin of Adyghe State University. Series 3: Pedagogy and Psychology. 2011;2:214–8 (In Russ.). EDN: OEDGUH

23. Beregovoy GT, Zavalova ND, Lomov BF, Ponomarenko VA. Experimental psychological research in aviation and cosmonautics. Moscow: Nauka; 1978 (In Russ.).