Abstract
Goal: To explore the possible impact of ionizing radiation in the pathophysiology of neuropsychiatric disorders amongst clean-up workers of the Chornobyl catastrophe (liquidators).Design, object, and methods: Retrospective-prospective study (1987–2015) of liquidators from the State Register of Ukraine (SRU) with radiation doses records and Clinical-Epidemiological Register (CER) of the State Institution ≪National Research Center for Radiation Medicine of the National Academy of Medical Sciences of Ukraine≫ (NRCRM). Moreover, cohort and cross-sectional studies of the randomized sample of liquidators from the CER (exposed group, 198 subjects) were examined. Internal control group included the liquidators irradiated in doses <50.0 mSv (42 persons). All subjects were assessed by a detailed clinical examination and a battery of standardized neuropsychiatric scales, psychometric, and neuropsychological tests. Descriptive and variation statistics, non-parametric criteria, regression-correlation analysis, survival analysis by Kaplan & Meier, and risk analysis were used.Results: Exposed group vs. control group showed cognitive disorders in 99 (50.0%) vs. 20 (18.1%), (P = 0.04); affective disorders in 96 (48.3%) vs. 36 (32.7%) (P = 0.007), and stress-related disorders in 115 (58.4%) vs. 8 (7.3%) (P < 0.001). In the main group exposed to ≥50 mSv vs. internal control group (exposed to <50 mSv), affective disorders were present, respectively, in 89 (56.4%) vs. 7 (19.1%) (P < 0.001), and stress-related disorders in 98 (62.8%) vs. 17 (40.4%) (P = 0.009). Relative risks (RR) and 95% confidential intervals (95%CI) of Incidence of some neuropsychiatric disorders in liquidators of 1986–1987 related to internal control (doses <50 mSv) were as follows: organic psychosis (RR = 3.15; 95% CI: 2.6; 3.7); non-psychotic organic brain damage (RR = 1.99; 95% CI: 1.6; 2.5); acute (RR = 1.40, 95% CI: 1.3; 1.5), and chronic cerebrovascular disorders (RR = 1.23; 95% CI 1.0;1.5). Neuropsychiatric diseases show a strong, increasing, and approximately quadratic statistically significant (Pv < 0.001) relationship with individual dose, yielding an estimated excess relative risk ERR = 2.76 Sv−2 (95% CI 1.06–7.15).Conclusions: Liquidators have an excess of cognitive, affective, and stress-related disorders. The risk of diseases rises with radiation dose. Radiation risks are revealed for organic psychoses, non-psychotic organic brain damage, acute and chronic cerebrovascular pathology.
Highlights
The Chornobyl disaster was a catastrophic nuclear accident that occurred on the 26th April 1986 at the No 4 nuclear reactor in the Chornobyl Nuclear Power Plant (ChNPP), near the city of Pripyat in the north of Ukraine (110 km from Kyiv), and it was the most serious accident ever to occur in the nuclear power industry
According to the register’s data (SRU), the incidence of organic, including symptomatic, mental disorders (ICD9: 293.0–294.9: ICD-10: F00-F05; F06.0, F06.2) was 101.99 per 10,000 persons, and it showed the highest statistically significant (Pv < 0.001) relative risk (RR = 3.15; 95% CI: 2.6; 3.7) (Table 2)
According to the survival analysis, we considered the time of the onset of any neuropsychiatric pathology after the Chornobyl accident measured in years as the event in which the pathology arose after the catastrophe
Summary
The Chornobyl disaster was a catastrophic nuclear accident that occurred on the 26th April 1986 at the No 4 nuclear reactor in the Chornobyl Nuclear Power Plant (ChNPP), near the city of Pripyat in the north of Ukraine (110 km from Kyiv), and it was the most serious accident ever to occur in the nuclear power industry. According to the International Nuclear and Radiological Event Scale (INES) the Chornobyl catastrophe was the highest, the 7th, level “major accident,” resulting in widespread health and environmental effects requiring implementation of planned and extended countermeasures [1]. There have been two accidents of this kind: the Chornobyl catastrophe [2] and Fukushima Daiichi nuclear disaster, a series of events beginning on 11 March 2011 [3, 4]. Radiological impact on people and environment of the Chornobyl catastrophe is around 10 times higher than that following the Fukushima Daiichi accident. According to the latest estimates [5], ∼1.8 EBq 131I radioactivity was thrown out of the destroyed ChNPP Unit, significantly higher than that following the Fukushima disaster. Worldwide annual exposure to natural radiation sources would generally be expected to be in the range 1–10 mSv, with 2.4 mSv being the present estimate of the central value [7]
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