Nested matched case control study for the Japan Fukushima Health Management Survey's first full-scale (second-round) thyroid examination

• Published in: Medicine (Baltimore) Vol. 99; no. 27; p. e20440
• Main Authors: Takahashi, Hideto, Yasumura, Seiji, Takahashi, Kunihiko, Ohira, Tetsuya, Ohtsuru, Akira, Midorikawa, Sanae, Suzuki, Satoru, Shimura, Hiroki, Ishikawa, Tetsuo, Sakai, Akira, Suzuki, Shinichi, Yokoya, Susumu, Tanigawa, Koichi, Ohto, Hitoshi, Kamiya, Kenji
• Format: Journal Article
• Language: English
• Published: United States the Author(s). Published by Wolters Kluwer Health, Inc 02.07.2020; Wolters Kluwer Health
• Subjects: Adolescent; Case-Control Studies; Female; Fukushima Nuclear Accident; Humans; Incidence; Japan - epidemiology; Male; Observational Study; Thyroid Gland - diagnostic imaging; Thyroid Neoplasms - diagnostic imaging; Thyroid Neoplasms - epidemiology; Ultrasonography; Japan
• ISSN: 0025-7974; 1536-5964; 1536-5964
• DOI: 10.1097/MD.0000000000020440

Since Fukushima nuclear accident in 2011, thyroid ultrasound examinations have been conducted. The first full-scale examination detected 71 thyroid-cancer cases. This study examined whether radiation exposure was associated with thyroid-cancer incidence.Subjects were participants in the baseline screening and newborns during the 2011 fiscal year. Under nested matched case-control study design, 10 controls per each case were selected by matching the age, sex, baseline screening results, and interval between examinations. With 3 dose levels of external radiation: 1.3 + mSv (upper), 0.8 to 1.3 (middle), and 0.0 to 0.8 (reference), we applied 2 logistic models adjusting for 3 participation-proportions (primary, secondary, and fine-needle aspiratory cytology), overweight, and the B-result of baseline screening (Model 1), and past medical history, family history of thyroid cancer, and frequencies of eating seafood and seaweed in addition to the parameters in Model 1 (Model 2). We examined each model in 3 ways: (a) excluding subjects with a missing radiation exposure dose; and substituting (b1) median or (b2) mean dose of the municipality with missing dose.Odds ratios (ORs) of middle-dose exposure were (a) 1.35 (0.46-3.94), (b1) 1.55 (0.61-3.96), and (b2) 1.23 (0.50-3.03) for Model 1, and (a) 1.18 (0.39-3.57), (b1) 1.31 (0.49-3.49), and (b2) 1.02 (0.40-2.59) for Model 2. For upper-dose exposure, similar results were obtained. Past medical history was significantly associated (odds ratio  = 2.04-2.08) with both (b1) and (b2) in Model 2.No significant associations were obtained between the external radiation exposure and thyroid-cancer incidence.