Nonparametric estimation of loss life expectancy of the Russian participants in clean-up operations following the Chernobyl accident

«Radiation and Risk», 2020, vol. 29, No. 3, pp.14-26

DOI: 10.21870/0131-3878-2020-29-3-14-26

Authors

Korelo A.M. – Senior Researcher. Contacts: 4 Korolyov str., Obninsk, Kaluga region, Russia, 249035. Tel.: (484) 399-32-47; e-mail: This email address is being protected from spambots. You need JavaScript enabled to view it. .
Maksioutov M.A. – Head of Dep., C. Sc., Tech.
Tumanov K.А. – Head of Lab., C. Sc., Biol.
Seleva N.G. – Engineer, C. Sc., Biol.
Kochergina E.V. – Head of Lab., C. Sc., Med.
Zelenskaya N.S. – Researcher
Lashkova O.E. – Researcher
Ivanov V.K. – Deputy Director, Chairman of RSCRP, Corresponding Member of RAS, D. Sc., Tech. A. Tsyb MRRC.

A. Tsyb MRRC, Obninsk

Abstract

This article describes the study of probable effects of ionizing radiation on changes in life expectan-cy of the Russian participants in clean-up operations following the Chernobyl accident (liquidators). For the study the data on mortality among the liquidators registered at the National Radiation Epi-demiological Registry were used. The follow-up study was started in 1992, at that time the study cohort consisted 66,615 males, their average age was 38.5 years, they resided in the entire territory of Russia. The liquidators were exposed to ionizing radiation during their clean-up work inside the Chernobyl exclusion zone in 1986 through 1987, the years of the largest radiation hazard and the most intensive clean-up operations, average radiation dose in the cohort was 132 mGy. The cohort was followed for 27 years. During this period 26 720 death cases with established cause of death were registered. Changes in the lifetime expectancy of the followed clean-up workers were estimat-ed with the methods for non-parametric survival analysis. Average survival time in various dose groups was estimated with data on aggregated and specific causes of death. From analysis it be-came clear that to measure effects of radiation on changes in the lifetime expectancy it is neces-sary to assess the contribution of each of the main causes of death, even if a cause is not associat-ed with radiation. The loss life expectancy caused by solid cancer was found in clean-up workers with doses ≥ 150 mGy. For 27-years of the follow-up study the life expectancy was reduced by 0.3 years per unit dose. If the follow-up study of effects of ionizing radiation on the loss life expectancy of the Chernobyl liquidators is continued, the loss life expectancy is probable to be pronounced.

Key words
survival analysis, nonparametric estimation, survival function, Kaplan-Meier method, competing risks, life expectancy, restricted mean survival time, solid cancer, circulatory system diseases, traumas and poisonings.

References

1. Santrock J.W. Life expectancy. A topical approach to life-span development. New York, McGraw-Hill Companies, Inc., 2007, pp. 128-132.

2. Human Development Report 2014. Technical Notes. Available at: http://hdr.undp.org/ sites/default/files/hdr14_technical_notes.pdf (Accessed 06.07.2020).

3. Radiation Safety Standards (RSS-99/2009). Sanitary-epidemiological rules and standards. Moscow, Federal Center of Hygiene and Epidemiology of Rospotrebnadzor, 2009. 100 p. (In Russian).

4. Anderson R.N. Method for constructing complete annual U.S. life tables. National Center for Health Statis-tics. Vital Health Stat., 1999, vol. 2, no. 129, pp. 1-28.

5. Gorski А.I., Maksioutov М.А., Tumanov K.A., Kochergina E.V., Ivanov V.K. Impact of radiation factor on average survival time for Chernobyl clean-up workers with solid cancer. Radiatsionnaya biologiya. Radioekologiya – Radiation Biology. Radioecology, 2019, vol. 59, no. 1, pp. 37-45. (In Russian).

6. Baade P.D., Youlden D.R., Andersson T.M., Youl P.H., Kimlin M.G., Aitken J.F., Biggar R.J. Estimating the change in life expectancy after a diagnosis of cancer among the Australian population. BMJ Open, 2015, vol. 5, no. 4, pp. 1-7.

7. Dehbi H.M., Royston P., Hackshaw A. Life expectancy difference and life expectancy ratio: two measures of treatment effects in randomized trials with non-proportional hazards. BMJ, 2017, vol. 357, pp. 1-7.

8. Kaplan E.L., Meier P. Nonparametric estimation from incomplete observations. J. Amer. Statist. Assoc., 1958, vol. 53, no. 282, pp. 457-481.

9. Kleinbaum D.G., Klein M. Survival analysis. A self‐learning text. Third edition. New York, Springer-Verlag, 2012.

10. Handbook of survival analysis. Eds.: J.P. Klein, H.C. van Houwelingen, J.G. Ibrahim, T.H. Scheike. New York, Chapman and Hall/CRC, 2014. 656 p.

11. Therneau T.M., Crowson C.S., Atkinson E.J. Adjusted survival curves. 2015. Available at: https://cran.r-project.org/web/packages/survival/vignettes/adjcurve.pdf (Accessed 06.07.2020).

12. Tian L., Zhao L., Wei L.J. Predicting the restricted mean event time with the subject’s baseline covariates in survival analysis. Biostatistics, 2014, vol. 15, no. 2, pp. 222-233.

13. Kalbfleisch J.D., Prentice R.L. The statistical analysis of survival time data. New York, John Wiley, 1980, pp. 223-224.

14. Zhang M.-J., Fine J. Summarizing differences in cumulative incidence functions. Stat. Med., 2008, vol. 27, no. 24, pp. 4939-4949.

15. Lyu J., Chen J., Hou Y., Chen Z. Comparison of two treatments in the presence of competing risks. Pharmaceutical Statistics, 2020. DOI: 10.1002/pst.2028.

16. The R Project for Statistical Computing. Available at: https://www.r-project.org/ (Accessed 06.07.2020).

17. Health effects of Chernobyl: prediction and actual data 30 years after the accident. Eds.: Corresponding Member of RAS Ivanov V.K., Corresponding Member of RAS Kaprin A.D. Moscow, GEOS, 2015. 450 p. (In Russian).

18. Ivanov V.K., Karpenko S.V., Kashcheev V.V., Chekin S.Yu., Maksioutov M.A., Tumanov K.A., Shchukina N.V., Kochergina E.V., Zelenskaya N.S., Lashkova O.E., Ivanov S.A., Kaprin A.D. Radiation risks of Russian liquidators of the Chernobyl accident for the period 1992-2017. Part II: Solid cancer mortali-ty. Radiatsiya i risk – Radiation and Risk, 2020, vol. 29, no. 1, pp. 18-31. (In Russian).

19. ICD-10 Version 2019. Available at://icd.who.int/browse10/2019/en (Accessed 06.07.2020).

20. Gorsky A.I., Maksioutov M.A., Tumanov K.A, Kochergina E.V., Ivanov V.K. Mortality among Chernobyl emergency workers from 1992 over 2010: analysis of data of the National Radiation and Epidemiological Registry. Radiatsiya i risk – Radiation and Risk, 20130, vol. 22, no. 2, pp. 35-51. (In Russian).

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