Mortality Proportionate Analysis of Cancer and Non-Cancer Diseases Among the Residents of Kazakhstan Exposed to Radiation from the Semipalatinsk Nuclear Test Site: Evidence from the State Scientific Automated Medical Registry

Introduction: The State Scientific Automated Medical Registry (SSAMR) of Residents of Kazakhstan Exposed to Radiation is a unique source of information for scientific research on the impact of radiation on population health. We aimed to conduct a proportionate mortality analysis in the study group compared with the low-dose reference group. Materials and methods: This descriptive study examined decedents exposed to radiation who resided in territories affected by the Semipalatinsk Nuclear Test Site from 1949 to 1990. The study utilises data from the SSAMR Mortality Subregistry, which contains 8580 individuals who lived in the Abay and Beskaragay districts and were included in the study group and 3340 individuals who lived in the Kokpekty district and were included in the low-dose reference group. Results: The results were examined for outcomes of radiation exposure and for differences in the proportional structure of recorded deaths between the study and low-dose reference groups. Most proportions of deaths in the registry members residing in zones of extreme and maximal radiation risk were cardiovascular diseases, 39.6% (3399), solid cancers, 19.7% (1693), non-cancer pulmonary diseases, 13.3% (1140), and external causes of mortality, 9.4% (803). At the same time, the proportional mortality structure of the low-dose reference group was different, with deaths from cardiovascular diseases (CVD), 49.2% (1644), solid cancers (SC) accounting for 13.4% (447) of deaths, external causes of mortality accounting for 12% (401), and non-cancer pulmonary diseases accounting for 10.7% (358). The largest proportion of recorded deaths among the decedents from 0 to 14, and especially among boys, was due to lung diseases. CVDs were the majority of documented deaths in the age group of 65 and older, prevailing in women more than in men. A similar pattern was observed in the age group 15–64 years, though the proportion was lower by 10% in women and 3% in men in this age group. Compared with the study group, the low-dose reference group had a higher percentage of reported deaths due to CVD. Solid cancers constituted a considerable proportion in both age groups (15–64 and 65 and older) in the study group, compared with the low-dose reference group. Conclusions: Ionising radiation can have diverse effects on the health of living organisms, causing various cancers and potentially other non-cancer diseases. Our study demonstrated that solid cancer mortality odds significantly increased by 4.0% per 100-mSv increase in cumulative radiation dose (MOR = 1.040, 95% CI: 1.012–1.070, p = 0.0057). We also found associations between radiation exposure and deaths from non-cancer gastrointestinal diseases and non-cancer respiratory diseases. The results, based on updated data from the SSAMR, are important for understanding the long-term consequences of nuclear tests and for developing public health and social policies for the affected population.