Impact of the COVID-19 pandemic on all-cause mortality in the Ozersk urban district

Introduction. In the context of the COVID-19 pandemic, which has impacted all-cause excess mortality, it appears relevant to evaluate the synergistic effects of occupational radiation exposure and the SARS-CoV-2 infectious agent on the overall mortality in the population of a nuclear industry city. This is especially important for increasing the effectiveness of health protection and prevention measures among population and professionals.

Objective. A retrospective analysis of all-cause mortality rates in the population of the Ozersk urban district (OUD) during the COVID-19 pandemic, adjusted for the influence of radiation and non-radiation risk factors.

Materials and methods. A retrospective cohort study among residents of the Ozersk urban district who died from various causes in 2020– 2023 was conducted. Annual reports from Rosstat and the Municipal Statistics department were analyzed. Data on COVID-19 morbidity and mortality were provided by the Center for Hygiene and Epidemiology No. 71 in Ozersk. The survival function was assessed depending on COVID-19 status, with adjustment for age and external occupational radiation dose among workers of the Mayak Production Association, using the Kaplan–Meier method. The impact of COVID-19, considering occupational radiation dose, on all-cause mortality rates was analyzed using the Cox proportional hazards model.

Results. The analysis of mortality rate dynamics revealed the period associated with the peak of pandemic all-cause mortality in the OUD population. A significant influence of COVID-19 (p < 0.05) on all-cause mortality during the pandemic period, dependent on attained age and occupational radiation dose, was revealed. It was demonstrated that the pronounced effect of COVID-19 on all-cause mortality was a consequence of the multiplicative influence of several risk factors, among which attained age and external radiation dose had a significant impact.

Conclusions. The excess all-cause mortality rate in the OUD population during the pandemic period compared to the corresponding rate for the population of Russian Federation is a consequence of the impact of risk factors specific to population residing in the vicinity of nuclear industrial facilities. The results obtained are of interest for forecasting the potential detriment associated with the emergence of possible future pandemic situations.

1. Osipov MV, Sokolova VA, Kushnir AS. Evaluation of the impact of COVID-19 pandemic on overall mortality in Ozersk urban district. Extreme Medicine. 2022;24(2):74–80 (In Russ). https://doi.org/10.47183/mes.2022.011

2. Osipov MV, Fomin EP. Assessment of COVID-19 pandemic-related detrimental impact on the population of nuclear city population: Two-year results. Russian Open Medical Journal. 2023;12:e0101. https://doi.org/10.15275/rusomj.2023.0101

3. Zhang JJ, Dong X, Liu GH, Gao YD. Risk and Protective Factors for COVID-19 Morbidity, Severity, and Mortality. Clinical Reviews in Allergy and Immunology. 2023;64(1):90–107. https://doi.org/10.1007/s12016-022-08921-5

4. Novoselov VN, Nosach YuF, Entyakov BN. Atomic heart of Russia. Ed. Baranov SV. Chelyabinsk: Autograph, 2014 (In Russ.).

5. Shilnikova NS, Preston DL, Ron E, Gilbert ES, Vassilenko EK, Romanov SA, et al. Cancer mortality risk among workers at the Mayak nuclear complex. Radiation Research. 2003;159(6):787–98. https://doi.org/10.1667/0033-7587(2003)159[0787:cmrawa]2.0.co;2

6. Sokolnikov M, Preston D, Gilbert E, Schonfeld S, Koshurnikova N. Radiation effects on mortality from solid cancers other than lung, liver, and bone cancer in the Mayak worker cohort: 1948–2008. PLoS One. 2015;10(2):e0117784. https://doi.org/10.1371/journal.pone.0117784

7. Moseeva MB, Azizova TV, Grigoryeva ES, Haylock R. Risks of circulatory diseases among Mayak PA workers with radiation doses estimated using the improved Mayak Worker Dosimetry System 2008. Radiation and Environmental Biophysics. 2014;53(2):469–77. https://doi.org/10.1007/s00411-014-0517-x

8. Gomes AP, Costa B, Marques R, Nunes V, Coelho C. Kaplan–Meier Survival Analysis: Practical Insights for Clinicians. Acta Medica Portuguesa. 2024;37(4):280–5. https://doi.org/10.20344/amp.21080

9. Singh R, Mukhopadhyay K. Survival analysis in clinical trials: Basics and must know areas. Perspectives in Clinical Research. 2011;2(4):145–8. https://doi.org/10.4103/2229-3485.86872

10. Koshurnikova NA, Shilnikova NS, Okatenko PV. Characteristics of the cohort of workers at the Mayak nuclear complex. Radiation Research. 1999;152(4):352–63.

11. Deo SV, Deo V, Sundaram V. Survival analysis–part 2: Cox proportional hazards model. Indian Journal of Thoracic and Cardiovascular Surgery. 2021;37(2):229–33. https://doi.org/10.1007/s12055-020-01108-7

12. Telnov VI, Tretyakov FD. Dynamics of age and sex structure of the population of Ozersk (1953–2008). Extreme Medicine. 2009;4:108–22 (In Russ.).

13. Azizova TV, Muirhead CR, Moseeva MB, Grigoryeva ES, Sumina MV, O’Hagan J, et al. Cerebrovascular diseases in nuclear workers first employed at the Mayak PA in 1948–1972. Radiation and Environmental Biophysics. 2011;50(4):539–52. https://doi.org/10.1007/s00411-011-0377-6

14. Otto SP, Day T, Arino J, Colijn C, Dushoff J, Li M, et al. The origins and potential future of SARS-CoV-2 variants of concern in the evolving COVID-19 pandemic. Current Biology. 2021;31:R918–29. https://doi.org/10.1016/j.cub.2021.06.049

15. Chavez-MacGregor M, Lei X, Zhao H, Scheet P, Giordano SH. Evaluation of COVID-19 Mortality and Adverse Outcomes in US Patients with or without Cancer. JAMA Oncology. 2022;8(1):69–78. https://doi.org/10.1001/jamaoncol.2021.5148

16. Stram DO, Sokolnikov M, Napier BA, Vostrotin VV, Efimov A, Preston DL. Lung Cancer in the Mayak Workers Cohort: Risk Estimation and Uncertainty Analysis. Radiation Research. 2021;195(4):334–46. https://doi.org/10.1667/RADE-20-00094.1