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Life Span Study (LSS)

The Life Span Study (LSS) is a research program investigating life-long health effects based on epidemiologic (cohort and case-control) studies. Its major objective is to investigate the long-term effects of A-bomb radiation on causes of death and incidence of cancer. About 120,000 subjects selected from residents of Hiroshima and Nagasaki identified through the national census in 1950 have been followed since that time, including 94,000 atomic-bomb survivors and 27,000 unexposed individuals.

The LSS participants were initially interviewed concerning the circumstances of their exposure and have been subsequently contacted through mail-survey questionnaires, which provide data on other factors, such as lifestyle, that are relevant to disease occurrence and death. Based on this cohort, it is possible to conduct studies of the rates of occurrence of cancer and the causes of death related to radiation and other factors.

Periodic analyses of the LSS cohort data form the basis of a series of reports on mortality (death from cancer as well as other causes) and cancer incidence (rate of occurrence). The cohort is also the basis for more in-depth studies of individual cancer sites, often conducted through case-control studies. In such studies, molecular analysis of cancerous tissue samples from survivors is conducted to further elucidate the mechanisms of radiation-related cancer and the impact of other factors.