Cognitive effects of low dose of ionizing radiation – Lessons learned and research gaps from epidemiological and biological studies

The last decades have seen increased concern about the possible effects of low to moderate doses of ionizing radiation (IR) exposure on cognitive function. An interdisciplinary group of experts (biologists, epidemiologists, dosimetrists and clinicians) in this field gathered together in the framework of the European MELODI workshop on non-cancer effects of IR to summarise the state of knowledge on the topic and elaborate research recommendations for future studies in this area. Overall, there is evidence of cognitive effects from low IR doses both from biology and epidemiology, though a better characterization of effects and understanding of mechanisms is needed. There is a need to better describe the specific cognitive function or diseases that may be affected by radiation exposure. Such cognitive deficit characterization should consider the human life span, as effects might differ with age at exposure and at outcome assessment. Measurements of biomarkers, including imaging, will likely help our understanding on the mechanism of cognitive-related radiation induced deficit. The identification of loci of individual genetic susceptibility and the study of gene expression may help identify individuals at higher risk. The mechanisms behind the radiation induced cognitive effects are not clear and are likely to involve several biological pathways and different cell types. Well conducted research in large epidemiological cohorts and experimental studies in appropriate animal models are needed to improve the understanding of radiation-induced cognitive effects. Results may then be translated into recommendations for clinical radiation oncology and imaging decision making processes. The writing of this review was supported by the Multidisciplinary European Low Dose Initiative (MELODI) association which funded the organization of a workshop dedicated to the non-cancer effects of ionizing radiation, the conclusions of which concerning cognitive effects are presented in this article. The authors thank the CONCERT European Joint Program [H2020 Euratom grant number 662287] for additional financial support of the 2019 MELODI workshop. This publication reflects only the authors’ view. Responsibility for the information and views expressed therein lies entirely with the authors. The European Commission is not responsible for any use that may be made of the information it contains.