Long-term follow-up of atomic bomb survivors.

The Life Span Study (LSS) is a follow-up study of atomic bomb (A-bomb) survivors to investigate the radiation effects on human health and has collected data for over 60 years. The LSS cohort consists of 93,741 A-bomb survivors and another 26,580 age and sex-matched subjects who were not in either city at the time of the bombing. Radiation doses have been computed based on individual location and shielding status at the time of the bombings. Age at death and cause of death are gathered through the Japanese national family registry system and cancer incidence data have been collected through the Hiroshima and Nagasaki cancer registries. Noncancer disease incidence and health information are collected through biannual medical examinations among a subset of the LSS. Radiation significantly increases the risks of death (22% at 1 Gy), cancer incidence (47% at 1 Gy), death due to leukemia (310% at 1 Gy), as well as the incidence of several noncancer diseases (e.g. thyroid nodules, chronic liver disease and cirrhosis, uterine myoma, and hypertension). Significant effects on maturity (e.g. growth reduction and early menopause) were also observed. Long-term follow-up studies of the A-bomb survivors have provided reliable information on health risks for the survivors and form the basis for radiation protection standards for workers and the public.