Tetsuya Ohira1,2, Akira Ohtsuru1,3, Sanae Midorikawa1,3, Hideto Takahashi1,4, Seiji Yasumura1,5, Satoru Suzuki1, Takashi Matsuzuka1,6, Hiroki Shimura1,7, Tetsuo Ishikawa1,8, Akira Sakai1,9, Shinichi Suzuki10, Shunichi Yamashita1,11, Susumu Yokoya1,12, Koichi Tanigawa1, Hitoshi Ohto1, Kenji Kamiya1,13. 1. From the Radiation Medical Science Center for the Fukushima Health Management Survey, Fukushima Medical University, Fukushima, Japan. 2. Department of Epidemiology, Fukushima Medical University School of Medicine, Fukushima, Japan. 3. Department of Radiation Health Management, Fukushima Medical University School of Medicine, Fukushima, Japan. 4. National Institute of Public Health, Saitama, Japan. 5. Department of Public Health, Fukushima Medical University School of Medicine, Fukushima, Japan. 6. Department of Otorhinolaryngology, Fukushima Medical University School of Medicine, Fukushima, Japan. 7. Department of Laboratory Medicine, Fukushima Medical University School of Medicine, Fukushima, Japan. 8. Department of Radiation Physics and Chemistry, Fukushima Medical University School of Medicine, Fukushima, Japan. 9. Department of Radiation Life Sciences, Fukushima Medical University School of Medicine, Fukushima, Japan. 10. Department of Thyroid and Endocrinology, Fukushima Medical University School of Medicine, Fukushima, Japan. 11. Atomic Bomb Disease Institute, Nagasaki University, Nagasaki, Japan. 12. Thyroid and Endocrine Center, Fukushima Medical University, Fukushima, Japan. 13. Research Institute for Radiation Biology and Medicine, Hiroshima University, Hiroshima, Japan.
Abstract
BACKGROUND: The 2011 Great East Japan Earthquake led to a nuclear accident at Fukushima Daiichi Nuclear Power Plant. This study examines the associations of radiation dose and lifestyle factors with incidence of thyroid cancer in Fukushima. METHODS: We designed a prospective study with 300,473 participants aged 18 years or younger, who underwent thyroid examinations from October 2011. Follow-up surveys were conducted through June 2017, and 245,530 participants (123,480 men and 122,050 women, 82% follow-up) received follow-up examinations. Fukushima Prefecture was divided into five areas based on individual external radiation dose. We calculated relative risks and 95% confidence intervals (CIs) for thyroid cancer in each area, with area of lowest dose as reference, using age-adjusted Poisson regression models. We also calculated risks associated with overweight and obesity. RESULTS: The incidence per 100,000 for Groups A (highest dose), B, C, D, and E (lowest dose) were 13.5, 19.2, 17.3, 9.0, and 8.3, respectively. Compared with Group E, the age-adjusted risks (95% CIs) were 1.62 (0.59, 4.47) for group A, 2.32 (0.86, 6.24) for group B, 2.21 (0.82, 5.94) for group C, and 1.02 (0.36, 2.86) for group D. Obesity was positively associated with thyroid cancer incidence; the multivariable-adjusted risk of thyroid cancer was 2.23 (1.01, 4.90) for obese individuals compared with nonobese individuals. CONCLUSION: Regional differences in radiation dose were not associated with increased risk of thyroid cancer among children in Fukushima within 4 to 6 years after the nuclear power plant accident. Obesity may be an important factor for further follow-up in Fukushima.
BACKGROUND: The 2011 Great East Japan Earthquake led to a nuclear accident at Fukushima Daiichi Nuclear Power Plant. This study examines the associations of radiation dose and lifestyle factors with incidence of thyroid cancer in Fukushima. METHODS: We designed a prospective study with 300,473 participants aged 18 years or younger, who underwent thyroid examinations from October 2011. Follow-up surveys were conducted through June 2017, and 245,530 participants (123,480 men and 122,050 women, 82% follow-up) received follow-up examinations. Fukushima Prefecture was divided into five areas based on individual external radiation dose. We calculated relative risks and 95% confidence intervals (CIs) for thyroid cancer in each area, with area of lowest dose as reference, using age-adjusted Poisson regression models. We also calculated risks associated with overweight and obesity. RESULTS: The incidence per 100,000 for Groups A (highest dose), B, C, D, and E (lowest dose) were 13.5, 19.2, 17.3, 9.0, and 8.3, respectively. Compared with Group E, the age-adjusted risks (95% CIs) were 1.62 (0.59, 4.47) for group A, 2.32 (0.86, 6.24) for group B, 2.21 (0.82, 5.94) for group C, and 1.02 (0.36, 2.86) for group D. Obesity was positively associated with thyroid cancer incidence; the multivariable-adjusted risk of thyroid cancer was 2.23 (1.01, 4.90) for obese individuals compared with nonobese individuals. CONCLUSION: Regional differences in radiation dose were not associated with increased risk of thyroid cancer among children in Fukushima within 4 to 6 years after the nuclear power plant accident. Obesity may be an important factor for further follow-up in Fukushima.