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RERF Glossary

Life Span Study: Detailed description of the study population

The Life Span Study population consists of about 120,000 persons who were selected on the basis of data from the 1950 Japanese National Census. This population includes proximally exposed and distally exposed atomic-bomb survivors living in Hiroshima or Nagasaki and nonexposed controls.

The original LSS sample consisted of about 99,000 persons. Basically, all persons in the Master Sample who were located less than 2,500 meters from the hypocenter ATB were included in the LSS sample, with about 28,000 persons exposed at less than 2,000 meters serving as the core. Equal numbers of persons who had been located 2,500-9,999 meters from hypocenter ATB and persons NIC ATB were selected to match the core group by age and sex. All persons in city ATB were identified by means of supplementary schedules of the 1950 national census. The NIC group was identified by other means (see Atomic Bomb Casualty Commission Technical Reports 4-59 and 15-63). Both the Pathology Sample of about 70,000 persons and the original 20,000 persons in the Adult Health Study were subsets of the LSS sample. In 1970 about 10,000 persons exposed at distances less than 2,500 meters from hypocenter in the reserve part of the Master Sample were added (and designated as the "extended LSS") for the sixth LSS report (1950-1970) (ABCC Technical Report 10-71; S Jablon, H Kato, Radiat Res 50:649-98, 1972) and continued as the base population until the addition of about 11,000 persons who had been exposed in Nagasaki at 2,500-9,000 meters from hypocenter (RERF Technical Report 1-86; DL Preston et al, Radiat Res 111:151-78, 1987). The extended LSS sample plus the added persons from Nagasaki were designated as the LSS-E85. Radiation dose estimates, according to Dosimetry System 1986 (DS86), are available for the majority of the LSS survivors. The average dose received by exposed survivors in this population was 0.16 Gy.

The entire LSS cohort totals about 94,000 persons, which does not include persons NIC ATB. As of 1995, more than 50% of LSS cohort members are still alive. As of the end of 1990, almost 38,000 deaths have occurred in this group, including about 8,000 cancer deaths among the 87,000 survivors. Approximately 430 of these cancer deaths are estimated to be attributable to radiation.