THYROID-DISEASES AMONG ATOMIC-BOMB SURVIVORS IN NAGASAKI

Objective.-To elucidate the current thyroid disease status for the Nag asaki Adult Health Study cohort of the Radiation Effects Research Foun dation. Design.-Survey study. Setting.- Nagasaki, Japan. Participants. -Cohort members of the Nagasaki Adult Health Study who received bienni al health examinations from October 1984 to April 1987 (n=2856). A tot al of 2587 subjects remained after exclusion of persons exposed in Hir oshima or in utero and those who were not in Nagasaki at the time of t he bombing. Thyroid radiation dose by the dosimetry system established in 1986 was available for 1978 of the 2587 subjects. Main Outcome Mea sures.-Thyroid diseases were diagnosed using uniform procedures includ ing ultrasonic scanning. The relationship of the prevalence of each th yroid disease with thyroid radiation dose, sex, and age was analyzed u sing logistic models. Results.-A significant dose-response relationshi p was observed for solid nodules, which include cancer, adenoma, adeno matous goiter, and nodules without histological diagnosis, and for ant ibody-positive spontaneous hypothyroidism (autoimmune hypothyroidism) but not for other diseases. The prevalence of solid nodules showed a m onotonic dose-response relationship, yet that of autoimmune hypothyroi dism displayed a concave dose-response relationship reaching a maximum (+/-SE) level of 0.7 +/- 0.2 Sv. Conclusions.-The present study confi rmed the results of previous studies by showing a significant increase in solid nodules with dose to the thyroid and demonstrated for the fi rst time a significant increase in autoimmune disease among atomic bom b survivors. A concave dose-response relationship indicates the necess ity for further studies on the effects of relatively low doses of radi ation on thyroid disease.