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Original Investigation
February 2015

Association of Radiation Dose With Prevalence of Thyroid Nodules Among Atomic Bomb Survivors Exposed in Childhood (2007-2011)

Author Affiliations
  • 1Department of Clinical Studies, Radiation Effects Research Foundation, Nagasaki, Japan
  • 2First Department of Internal Medicine, Graduate School of Biochemical Sciences, Nagasaki University, Nagasaki, Japan
  • 3Department of Statistics, Radiation Effects Research Foundation, Nagasaki, Japan
  • 4Department of Metabolism/Diabetes and Clinical Nutrition, Nagasaki University Hospital, Nagasaki, Japan
  • 5Department of Internal Medicine, Yachiyo Hospital, Akitakata, Japan
  • 6Hiroshima Atomic Bomb Casualty Council, Hiroshima, Japan
  • 7Department of Thyroid Surgery, Nakajima Tsuchiya Clinic, Hiroshima, Japan
  • 8International Hibakusha Medical Center, Nagasaki University Hospital, Nagasaki, Japan
JAMA Intern Med. 2015;175(2):228-236. doi:10.1001/jamainternmed.2014.6692

Importance  Few studies have evaluated the association of radiation dose with thyroid nodules among adults exposed to radiation in childhood.

Objective  To evaluate radiation dose responses on the prevalence of thyroid nodules in atomic bomb survivors exposed in childhood.

Design, Setting, and Participants  This survey study investigated 3087 Hiroshima and Nagasaki atomic bomb survivors who were younger than 10 years at exposure and participated in the thyroid study of the Adult Health Study at the Radiation Effects Research Foundation. Thyroid examinations including thyroid ultrasonography were conducted between October 2007 and October 2011, and solid nodules underwent fine-needle aspiration biopsy. Data from 2668 participants (86.4% of the total participants; mean age, 68.2 years; 1213 men; and 1455 women) with known atomic bomb thyroid radiation doses (mean dose, 0.182 Gy; median dose, 0.018 Gy; dose range, 0-4.040 Gy) were analyzed.

Main Outcomes and Measures  The prevalence of all thyroid nodules having a diameter of 10 mm or more (consisting of solid nodules [malignant and benign] and cysts), prevalence of small thyroid nodules that were less than 10 mm in diameter detected by ultrasonography, and atomic bomb radiation dose-responses.

Results  Thyroid nodules with a diameter of 10 mm or more were identified in 470 participants (17.6%): solid nodules (427 cases [16.0%]), malignant tumors (47 cases [1.8%]), benign nodules (186 cases [7.0%]), and cysts (49 cases [1.8%]), and all were significantly associated with thyroid radiation dose. Excess odds ratios per gray unit were 1.65 (95% CI, 0.89-2.64) for all nodules, 1.72 (95% CI, 0.93-2.75) for solid nodules, 4.40 (95% CI, 1.75-9.97) for malignant tumors, 2.07 (95% CI, 1.16-3.39) for benign nodules, and 1.11 (95% CI, 0.15-3.12) for cysts. The interaction between age at exposure and the dose was significant for the prevalence of all nodules (P = .003) and solid nodules (P < .001), indicating that dose effects were significantly higher with earlier childhood exposure. No interactions were seen for sex, family history of thyroid disease, antithyroid antibodies, or seaweed intake. No dose-response relationships were observed for small (<10-mm diameter) thyroid nodules.

Conclusions and Relevance  Radiation effects on thyroid nodules exist in atomic bomb survivors 62 to 66 years after their exposure in childhood. However, radiation exposure is not associated with small thyroid nodules.