Atomic Bomb Survivors, Higher Radiation and Thyroid Diseases
Radiation and Thyroid Disease
Survivors of the two atomic bombs in Japan 60 years ago who had a higher exposure to radiation now have a greater incidence of certain thyroid diseases, including tumors and cysts, and that risk increases with being younger at the time of exposure, according to a study in the March 1 issue of JAMA.
Thyroid disease has become an important target with which to study the effects of radiation. Many studies have reported that the risk for malignant and benign thyroid nodules increased with external and internal radiation exposure in people exposed at young ages, although few studies have followed exposed populations for long periods, such as more than 50 years, according to background information in the article.
Misa Imaizumi, M.D., of the Radiation Effects Research Foundation, Nagasaki and Hiroshima, Japan, and colleagues conducted a comprehensive thyroid disease survey between 2000 and 2003 to diagnose thyroid nodules (malignant and benign) and autoimmune thyroid diseases in survivors of the 1945 atomic bombs in Hiroshima and Nagasaki. The researchers determined the radiation dose-response relationships for these thyroid diseases. The study included 4,091 participants (average age, 70).
Thyroid diseases were identified in 44.8 percent of the total participants. In 3,185 participants, excluding persons exposed in utero, not in the city at the time of the atomic bombings, or with unknown radiation dose, the prevalence of all solid nodules, malignant tumors, benign nodules, and cysts was 14.6 percent, 2.2 percent, 4.9 percent, and 7.7 percent, respectively. The prevalence of all solid nodules, malignant tumors, benign nodules and cysts was significantly associated with thyroid radiation dose.
The researchers estimate that 28 percent of all solid nodules, 37 percent of malignant tumors, 31 percent of benign nodules and 25 percent of cysts were associated with radiation exposure. No significant dose-response relationship was observed for positive antithyroid antibodies, antithyroid antibody