Objectives Providing sufficient information about potential benefits and harms is essential in decision-making about participation in screening programs. Thyroid cancer screening (CS) with ultrasound is generally considered harmful and is not currently recommended. However, after nuclear accidents, thyroid CS has historically been performed as part of radiation effect surveys and post-accident response. Influencing factors must be considered when providing decision-making information to people in the area surrounding the Fukushima nuclear accident regarding the local government-led present opt-out screening. We aimed to identify factors associated with the decision to participate in thyroid CS in Fukushima using a scenario-based questionnaire survey among young people of the same age as the subjects of this screening. Methods We presented a scenario to female university students as if they were offered thyroid CS after the nuclear accident, and asked whether they would participate. We then provided a handout currently used in Fukushima regarding the potential benefits and harms of the screening, and asked respondents again about their willingness to participate. Next, we provided a leaflet outlining specific examples of overdiagnosis and its harms, and gave lectures on radiation health risks, radiation exposure doses in Fukushima, and CS. We again asked about respondents' decisions about participation at each step. We assessed risk perception regarding cancer onset caused by radiation exposure and estimation of the potential benefits and harms of thyroid CS. Results 16% of the 76 questionnaire respondents included the real subjects for thyroid CS in Fukushima. Immediately after reading the scenario and after providing the existing handout, 75% and 60% of respondents said they would participate in the screening, respectively. The most common reason for participation was seeking reassurance. After providing the leaflet about overdiagnosis and its harms and after giving lectures, the proportions of respondents who chose to participate decreased to 19% and 11%, respectively. In contrast, the proportions of respondents who chose not to participate increased to 15%, 24%, 53%, and 66% at each step. Decision-making at each step was not related to cancer risk perception of radiation, but to the estimation of potential harms. Conclusions Many young residents participated in the local government-led thyroid CS in Fukushima because they were designated as targets. The current findings suggest that individuals chose to undergo screening to relieve anxiety when benefits were estimated to exceed harms. The handout currently used for thyroid CS does not adequately address overdiagnosis as the most significant harm of screening. Providing a leaflet with explanations of the harms of overdiagnosis changed the decision-making process and increased the number of respondents who chose not to participate because of potentially significant harmful effects. Furthermore, the decision to participate in the screening was influenced by explaining scientific evidence regarding low radiation exposure and low cancer risk from radiation in Fukushima, and the magnitude of overdiagnosis in thyroid CS. To develop adequate decision-making aids regarding CS with a high risk of overdiagnosis, specific tools explaining the harms of overdiagnosis are needed, in writing and through dialogue.

The worldwide issue of overdiagnosis of thyroid cancer has become a concern as a result of the frequent overdiagnosis of asymptomatic papillary thyroid cancer through fine-needle aspiration (FNA) cytology. To prevent such overdiagnosis, it is advisable to carefully consider the indication for FNA cytology in the evaluation of asymptomatic thyroid nodules, as population-wide thyroid screenings are not currently recommended. However, patients with thyroid nodules may desire reassurance through FNA cytology due to concerns about the possibility of cancer. In such cases, it is essential to inform patients about the risks and harms of overdiagnosis and overtreatment. This chapter aims to examine the psychosocial impact and ethical considerations surrounding the overdiagnosis of asymptomatic thyroid nodules, with a particular focus on children and young people, drawing upon lessons learned from the experience of thyroid cancer screening in Fukushima. FNA cytology is, in a sense, a team medical care with pathologists and clinicians. If clinicians lack an understanding of overdiagnosis and request cytological examination of asymptomatic patients, it is important for pathologists to call attention to the harms of overdiagnosis.

BACKGROUND:Overdiagnosis of thyroid cancer has become a major global medical issue. Ultrasound-based thyroid cancer screening has promoted overdiagnosis, and recently international recommendations state that it should not be conducted, even after a nuclear accident. The Fukushima thyroid cancer screening program was initiated in 2011 as a health policy after the nuclear accident. The risk of radiation-induced thyroid cancer was unlikely given the low radiation levels, but the thyroid cancer screening program has continued at 2-year intervals with a relatively high participation rate and is now in its fifth round. It is therefore crucial to clarify whether those targeted for screening understand the disadvantages of screening, and to identify factors that influenced their decision to participate. METHODS:We conducted an anonymous mail-based questionnaire among young people from Fukushima Prefecture (subjects) and a neighboring prefecture that was not targeted for screening (non-subjects). We asked them about the significance of the thyroid cancer screening in Fukushima Prefecture, their reasons for accepting or refusing screening, their perception of the harms of screening, and their opinions on thyroid examination at school. We compared the results of the questionnaire between subjects and non-subjects and between examinees (who were screened) and non-examinees (who declined screening). RESULTS:Only 16.5% of respondents were aware of the harms associated with thyroid cancer screening, with most perceiving that the benefits outweighed the harms. Comparison of subjects' and non-subjects' responses showed there were no significant differences between the two groups. Among subjects, there were also no differences in responses between examinees and non-examinees. The most common reason for participation in screening was that the screening was conducted in schools and perceived as obligatory. CONCLUSIONS:These results highlighted a serious ethical issue in that school-based screening leads to making young people think that it is mandatory screening in an opt-out and default setting manner, with a lack of knowledge about the disadvantages of screening. Based on the autonomy of the subjects and the ethical principle of the post-disaster, surveys after a nuclear disaster should be conducted in an opt-in style without an opt-out style such as school-based screening.

Various studies have investigated radiation risk perceptions after the accident at the Fukushima Daiichi Nuclear Power Station. However, student surveys are limited. This study aimed to investigate the perception of radiation risk among students aged 18-20 years who were in the 5th and 6th grades of elementary school at the time of the accident. We surveyed students in the Fukushima Prefecture and outside the prefecture. Out of all the data, 59% of the respondents were living in the Fukushima Prefecture at the time of the accident and 41% outside the prefecture. Trajectory analysis showed that changes in anxiety levels over time since 2011 could be divided into five classes: (a) the anxiety was the highest, and this tendency persisted. (b) High at the beginning, but decreased more quickly than class 1. (c) High at the beginning, but it diminished quickly. (d) Not high, but did not diminish easily in later years. (e) Low from the beginning, and persisted. Multinomial logistic analysis showed that among students living outside the prefecture at the time of the accident, a significantly higher proportion was in groups 4 and 5 than in group 2. A significant proportion of boys were present in groups 3, 4 and 5. A significant proportion of students whose current educational institutions were inside the prefecture were present in group 3. The level of anxiety was associated with the academic course, but not with subjective knowledge of radiation. In contrast, in the qualitative analysis of the free text, 31% considered 'knowledge about radiation' as the reason for the reduction in anxiety level. At the time of the investigation, most young people were not anxious about radiation. However, approximately 20% still had strong anxiety. We established that continuous risk communication is necessary. Furthermore, that stabilization and support related to life in general is important.

ABSTRACT The complex disaster of the Great East Japan Earthquake and the Fukushima nuclear accident caused concern about their various health impacts. Many types of intervention are desired as a countermeasure, depending on the phase of the disaster cycle. The importance of developing and applying codes of conduct has recently been emphasized for post-disaster investigations. Thyroid examination as a type of cancer screening survey was launched from October 2011 after the Fukushima nuclear accident as part of the Fukushima Health Management Survey. In this article, we reviewed the results of three rounds of thyroid examination from 2011 to 2018, and summarized the points to consider in the health survey conducted after the Fukushima nuclear accident. Large-scale mass screening by ultrasound thyroid examination resulted in many cancer diagnoses, >200 cases from a large reservoir of thyroid cancer that goes mainly unnoticed without screening. To prevent the harms of such over-diagnosis, we should be aware of the disadvantage of mass-screening based on the expected natural history of thyroid cancer. A change in strategy from mass-screening to individual monitoring is urgently needed according to international recommendations that are opposed to thyroid ultrasound cancer screening even after a nuclear disaster. To guarantee autonomy and informed choice on post-disaster disease monitoring for residents in a disaster-zone, it is important to set protocol participation and on a voluntary code of conduct basis.

Background Overdiagnosis of thyroid cancer has become a major global medical issue. Ultrasound-based thyroid cancer screening has promoted overdiagnosis, and recently international recommendations indicate that such screening should not be conducted, even after a nuclear accident. The Fukushima thyroid cancer screening program was initiated in 2011 as a health policy after the nuclear accident, although the risk for radiation-induced thyroid cancer was unlikely given the low radiation levels. However, the thyroid cancer screening program has continued at 2-year intervals with a relatively high participation rate and is now in its fifth round. Therefore, it is crucial to clarify whether those targeted for screening understand the disadvantages of screening and identify factors that influenced their decision to participate. Methods We conducted an anonymous mail-based questionnaire that included young people from Fukushima (subjects) and a neighboring prefecture that was not targeted for screening (non-subjects). We asked them about the significance of the thyroid cancer screening in Fukushima, the reasons for taking or not taking a screening, their perception of the harms of screening, and their opinions on thyroid examination at school. Then we compared the results of the questionnaire between subjects and non-subjects and examinees (who accepted screening) and non-examinees (who declined screening). Results Only 16.5% of respondents were aware of the harms associated with thyroid cancer screening, with most perceiving that the benefits outweighed the harms. Comparison of subjects’ and non-subjects’ responses showed there were no significant differences between subjects and non-subjects. In addition, among subjects, there were no differences of responses between examinees and non-examinees. The most common reason for participation in screening was that the screening was conducted in schools and perceived as obligatory. Conclusions These results highlighted a serious ethical issue in that school-based screening leads to making young people think that it is mandatory screening in an opt-out and default setting manner, with a lack of knowledge about the disadvantages of screening. Based on the autonomy of the subjects and the ethical principle of the post-disaster, surveys after a nuclear disaster should be conducted in an opt-in style without an opt-out style such as school-based screening.

Background The Great East Japan Earthquake and the Fukushima Daiichi nuclear disaster forced the evacuation of residents and led to many changes in lifestyle for the evacuees. The Comprehensive Health Check was implemented to support the prevention of lifestyle-related disease and we analyzed the effect of prolonged evacuation (average of 3.0 years) on the new onset of hyper-LDL cholesterolemia. Methods The study participants were Japanese adults living near the Fukushima Daiichi nuclear power plant in Fukushima Prefecture. Annual health checkups focusing on metabolic syndromes were conducted for persons ≥40 years by the Specific Health Checkup. Based on data from annual checkups from 2011 or 2012, we followed 18,670 participants without hyper-LDL cholesterolemia who underwent at least one other annual checkup during 2013–2015. Results We found that the new onset of hyper-LDL cholesterolemia was 31% higher in evacuees than in non-evacuees. Evacuees had a significantly higher prevalence of obesity, hypertension, and diabetes, and higher frequency of weight change. Furthermore, logistic regression model analysis showed that the evacuation was significantly associated with the new onset of hyper-LDL cholesterolemia after adjusting age, gender, body mass index, smoking habit, alcohol consumption, diabetes, weight change, sleep deprivation, and exercise. Conclusion The findings of the present study suggest that prolonged evacuation after a disaster is a risk factor for the new onset of hyper-LDL cholesterolemia, and lead to an increase in cardiovascular disease. It is therefore important to follow-up evacuees and recommend lifestyle changes where necessary.

We have been examining the Comprehensive Health Check of the Fukushima Health Management Survey of residents of 13 municipalities who were forced by the government to evacuate due to the 2011 Great East Japan Earthquake (GEJE). Our findings showed that evacuation is a risk factor for polycythemia and suggested that experiencing an unprecedented disaster and exposure to chronic stress due to evacuation might be a cause of polycythemia.We analyzed the relationship between the prevalence of polycythemia and the following factors observed in the Mental Health and Lifestyle Survey in an observational study with a cross-sectional design: traumatic symptoms, depression status, socioeconomic factors such as residential environment, and working situation after the GEJE. Target population of the survey included men and women who were at least 15 years of age and who lived in the evacuation zones specified by the government. Participants analyzed consisted of 29,474 persons (12,379 men and 16,888 women) who had participated in both the 2011 Comprehensive Health Check and Mental Health and Lifestyle Survey from June 2011 through March 2012.The prevalence of polycythemia was not associated with mental states associated with traumatic symptoms (Post-Traumatic Stress Disorder Checklist Scale ≥ 44) and depression status (Kessler 6-item Scale ≥ 13). Furthermore, multivariate analysis showed that there was a tendency for males to develop polycythemia, with characteristics such as being aged 65 years and older, highly educated, obese (body mass index ≥ 25), hypertensive, diabetic, having liver dysfunction, and a smoker being significantly related to the prevalence of polycythemia.Our findings conclusively demonstrated that polycythemia was not significantly related to psychological factors, but was significantly related to the onset of lifestyle-related disease after the GEJE.

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Supplemental Digital Content is available in the text Abstract 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.

Collective screening identifying endocrine diseases has not only the advantage of achieving early diagnosis but also the disadvantage of leading to overdiagnosis. Overdiagnosis involves the identification of diseases that would not have been diagnosed throughout the life course without screening. Therefore, diagnosis and treat‐ ment would actually be unnecessary for overdiagnosed patients throughout their life, and would also confer major disadvantages for them, not only physically but also psychosocially. When overdiagnosis of cancer occurs, the pathological diagnosis itself is correct, so overdiagnosis is completely different from misdiagnosis. Treatment in cases of overdiagnosis can be defined as overtreatment [1]. Clinicians may underestimate the disadvantages of overdiagnosis and overtreatment because it is not known in individual cases whether the diagnosis involves over‐ diagnosis or early detection that would benefit the patient [2]. There is also confusion in the use of the terms “over‐ diagnosis” and “overtreatment,” which obscures the harm inflicted when these occur. As a representative case of this, we would like to point out a couple of seriously misleading descriptions in the discussion of the article by Sakamoto et al. [3]. First, there is a misinterpretation of the term “over‐ treatment”. Sakamoto et al. [3] concluded that “problems concerning overtreatment basically do not occur in this survey” based on the cited paper, not on their analyzed data. They used the term “overtreatment” here simply to mean not performing excessive surgical treatment. How‐ ever, the NCI Dictionary of Cancer Terms defines “over‐ treatment” as follows: “Treatment of a cancer that would have gone away on its own or never caused any symp‐ toms. These cancers are usually found on a screening test. Overtreatment may lead to problems and harmful

Introduction Traumatic experiences and disordered sleep are strongly associated with drinking problems. We examined the effects of experiencing the Great East Japan Earthquake and subsequent nuclear power plant accident, and of sleep problems, on behavioral changes observed in nondrinkers. Methods This study examined cross-sectional data from the Mental Health and Lifestyle Survey conducted among residents in restricted areas of Fukushima in 2012. Participants were 21,454 evacuees aged 20 years or older at the time of disaster. People who did not drink before the disaster but became drinkers afterwards were compared with the rest of the cohort. We analyzed the association between behavioral changes in non-drinkers and potentially predictive variables, using logistic regression. Results The behavioral change of non-drinkers becoming drinkers (n=2,148) was significantly related to being male (OR=1.93, 95% CI : 1.74-2.15), being younger (21-49 yrs, OR=1.85, 95% CI : 1.60-2.13), having less educational attainment (up to high school graduate, OR=1.21, 95% CI : 1.091.35), smoking (OR=1.22, 95% CI : 1.08-1.38), losing family or relatives (OR=1.21, 95% CI : 1.071.37), change in employment (OR=1.19, 95% CI : 1.07-1.32), having severe sleep problems as measured by a Japanese version of the Athens Insomnia Scale (3-8, OR=1.45, 95% CI : 1.30-1.62), and severity of traumatic symptoms as measured by the PTSD Checklist Stressor-Specific (PCL-S) score (<44, OR=1.33, 95% CI : 1.17-1.51). Conclusion Having sleep problems and having more severe traumatic symptoms are significantly related to non-drinkers becoming drinkers.

AIM:The Fukushima Daiichi Nuclear Power Plant accident dramatically changed the lifestyle of residents who lived near the plant. We evaluated the association of metabolic syndrome (MetS) with specific lifestyle- and disaster-related factors in residents following the accident.METHODS:This cross-sectional study included 20,920 residents who underwent both the Comprehensive Health Check and the Mental Health and Lifestyle Survey from June 2011 to March 2012. Associations between MetS and lifestyle- and disaster-related factors, including psychological distress (post-traumatic stress disorder [PTSD]), were estimated using logistic regression analysis, adjusted for demographic and lifestyle factors, in 2019.RESULTS:MetS was present in 30.4% of men and 11.5% of women. There were significant differences in smoking, drinking status, and PTSD prevalence between subjects with and without MetS. Multivariable logistic regression analysis showed that age, quitting smoking, and low physical activity were significantly associated with MetS. Moreover, PTSD and light to moderate drinking were also significantly associated with MetS in women.CONCLUSIONS:Lifestyle- and disaster-related factors, including PTSD, were associated with MetS among subjects who lived near the Fukushima Daiichi Nuclear Power Plant accident.

Background The objectives of this study were to determine the longer-term trends in childhood obesity and hyperlipidemia among residents of Fukushima Prefecture 5 years after the Great East Japan Earthquake. Methods We evaluated the changes in height, weight, body mass index (BMI) standard deviation score (BMI-SDS), low-density lipoprotein-cholesterol (LDL-CHO), high-density lipoprotein-cholesterol (HDL-CHO), and triglyceride (TG) in residents aged 7-15 years who had lived in the evacuation zone between 2011 and 2015. Results (i) the mean BMI SDS in all residents in 2011 was 0.113, and the mean BMI-SDS in all residents gradually decreased from 2011 to 2015; (ii) serum LDL-CHO levels and TG levels in all residents with a BMI value >= 2SD in 2011 were higher than those in residents with a BMI value <2SD; (iii) the frequency of residents with an LDL-CHO level >= 140 mg/dl in 2012, 2013, and 2014 did not decrease in comparison with that in 2011, whereas the frequency of residents with an LDL-CHO level of >= 140 mg/dl in 2015 was lower than that in 2011. The frequency of residents with a TG level >= 120 mg/dl increased over the 5 years. Conclusions These results suggest that a number of pediatric residents suffered from obesity and hyperlipidemia. Furthermore, the long-term observation indicated an improvement in obesity, although the improvement in lipid abnormalities was delayed compared with that in obesity. Thus, it is necessary to continue with health checks for these residents with obesity and/or hyperlipidemia.

Background: After the Fukushima Daiichi Nuclear Power Plant accident, a preliminary ultrasound-based screening for thyroid cancer was conducted to establish a baseline for subsequent evaluations. In this survey, we assessed the relationship between the proportion of non-examinees and characteristics of the target populations. Methods: After summarizing a regional difference of non-examinees among the population of 359,200 (primary evaluation) and 2,246 (confirmatory testing) individuals who were living in Fukushima Prefecture on March 11, 2011, we estimated odds ratios (ORs) for each characteristic, including age, sex, area of residence, and moving after the accident, based on the proportion of non-examinees for the primary examination and the confirmatory testing, using a multivariate logistic regression model. Results: The dataset included 64,117 non-examinees (primary evaluation) and 194 (confirmatory testing). The logistic regression result indicated that girls were not likely to be non-examinees compared to boys, with adjusted OR of 0.80 (95% confidence interval [CI], 0.78–0.81) for the primary evaluation. Odds were lowest for children 6–10 years old (OR 0.26; 95% CI, 0.25–0.27), and higher for those 11–15 years old (OR 1.28; 95% CI, 1.25–1.32) and over 16 years old (OR 5.30; 95% CI, 5.16–5.43) when compared to children 0–5 years old. Individuals residing in the western part of the prefecture showed higher ORs. There was a higher proportion of non-examinees among those who moved after the accident compared to those who did not in the primary evaluation (OR 1.72; 95% CI, 1.64–1.79). Conclusions: In addition to demographic characteristics, a change of residence could be a potential factor that influenced the proportion of non-examinees. Our results will help proper interpretation of reports and prospective management of the survey.

In Reply In our observational study, 1 we comprehensively assessed the characteristics of thyroid cancer screened by ultrasonography among children and young adults with 2 rounds of examination during the first 5 years after the 2011 Fukushima Daiichi nuclear power station accident.The article by Takahashi et al 2 that Suzuki et al referred to was a simulation study of anticipated childhood and adolescent thyroid cancer cases in Japan that used a cancer progression model based on the National Cancer Registry.However, Figure 1 in our study was not based on the simulation model but on the exact detected cases in the thyroid examinations, the values of which were adjusted for the number of participants in each age group at the time of the accident.Suzuki et al highlighted the following 2 concerns: (1) goodness of fit should be shown and (2) detectable incidence function J(s) should be specifically checked to see whether or not it is dependent on age with evidence.Although these factors are significant for further analysis based on the simulation model, a recent analysis showed that ultrasonography screening-detected thyroid cancers do not have a linear progression but fall into a growth arrest in many young patients. 3Thus, future studies will be conducted to run simulation models based on theoretically reasonable tumor growth patterns of thyroid cancer in young patients based on ultrasonographic observation data from the Fukushima cohort.Akabayashi et al mentioned that the data corresponded to the baseline by the ultrasonography thyroid screening for children and the young adult population in Japan and highlighted the following 2 concerns for this study design: (1) the gradually decreasing participation rate over time and (2) the lack of large-scale controls.The participation rate from the first to the third round suggested by them was the value in the primary examination.Nevertheless, the confirmatory examinations of the third round of examination to confirm the diagnoses of the thyroid nodules are still ongoing.Recently, an international multidisciplinary expert group assessed the scientific evidence to formulate recommendations about longterm strategies for thyroid health monitoring after a nuclear power plant accident and published their findings in the International Agency for Research on Cancer Technical Publication. 4They developed 2 recommendations as follows: (1) against population thyroid screening after a nuclear accident and (2) considering offering a long-term thyroid monitoring program for higher-risk individuals after a nuclear accident.In the Fukushima situation, it is unethical to set a control group and induce an increased participation rate against the protocol of voluntary participation.To assess the health effects of low-dose exposures within the limits of the ethical conduct of such research, the ideal program would be initially conducted on a voluntary basis, with adequate information on both the benefit and harm of screening, and the program would be based on a conservative clinical examination in which only suspicious cancer cases are referred for ultrasonography to prevent overdiagnosis. 5Given that the risk for radiation-induced thyroid cancer is highest among children who are younger at the time of exposure, the comparison of age-group incidence between the second and third or subse-quent examinations should help elucidate the effects of radiation on health.

In Reply In our observational study, 1 we comprehensively assessed the characteristics of thyroid cancer screened by ultrasonography among children and young adults with 2 rounds of examination during the first 5 years after the 2011 Fukushima Daiichi nuclear power station accident.The article by Takahashi et al 2 that Suzuki et al referred to was a simulation study of anticipated childhood and adolescent thyroid cancer cases in Japan that used a cancer progression model based on the National Cancer Registry.However, Figure 1 in our study was not based on the simulation model but on the exact detected cases in the thyroid examinations, the values of which were adjusted for the number of participants in each age group at the time of the accident.Suzuki et al highlighted the following 2 concerns: (1) goodness of fit should be shown and (2) detectable incidence function J(s) should be specifically checked to see whether or not it is dependent on age with evidence.Although these factors are significant for further analysis based on the simulation model, a recent analysis showed that ultrasonography screening-detected thyroid cancers do not have a linear progression but fall into a growth arrest in many young patients. 3Thus, future studies will be conducted to run simulation models based on theoretically reasonable tumor growth patterns of thyroid cancer in young patients based on ultrasonographic observation data from the Fukushima cohort.Akabayashi et al mentioned that the data corresponded to the baseline by the ultrasonography thyroid screening for children and the young adult population in Japan and highlighted the following 2 concerns for this study design: (1) the gradually decreasing participation rate over time and (2) the lack of large-scale controls.The participation rate from the first to the third round suggested by them was the value in the primary examination.Nevertheless, the confirmatory examinations of the third round of examination to confirm the diagnoses of the thyroid nodules are still ongoing.Recently, an international multidisciplinary expert group assessed the scientific evidence to formulate recommendations about longterm strategies for thyroid health monitoring after a nuclear power plant accident and published their findings in the International Agency for Research on Cancer Technical Publication. 4They developed 2 recommendations as follows: (1) against population thyroid screening after a nuclear accident and (2) considering offering a long-term thyroid monitoring program for higher-risk individuals after a nuclear accident.In the Fukushima situation, it is unethical to set a control group and induce an increased participation rate against the protocol of voluntary participation.To assess the health effects of low-dose exposures within the limits of the ethical conduct of such research, the ideal program would be initially conducted on a voluntary basis, with adequate information on both the benefit and harm of screening, and the program would be based on a conservative clinical examination in which only suspicious cancer cases are referred for ultrasonography to prevent overdiagnosis. 5Given that the risk for radiation-induced thyroid cancer is highest among children who are younger at the time of exposure, the comparison of age-group incidence between the second and third or subse-quent examinations should help elucidate the effects of radiation on health.