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Background There is global concern over significant threats from a wide variety of environmental hazards to which children face. Large-scale and long-term birth cohort studies are needed for better environmental management based on sound science. The primary objective of the Japan Environment and Children’s Study (JECS), a nation-wide birth cohort study that started its recruitment in January 2011, is to elucidate environmental factors that affect children’s health and development. Methods/Design Approximately 100,000 expecting mothers who live in designated study areas will be recruited over a 3-year period from January 2011. Participating children will be followed until they reach 13 years of age. Exposure to environmental factors will be assessed by chemical analyses of bio-specimens (blood, cord blood, urine, breast milk, and hair), household environment measurements, and computational simulations using monitoring data (e.g. ambient air quality monitoring) as well as questionnaires. JECS’ priority outcomes include reproduction/pregnancy complications, congenital anomalies, neuropsychiatric disorders, immune system disorders, and metabolic/endocrine system disorders. Genetic factors, socioeconomic status, and lifestyle factors will also be examined as covariates and potential confounders. To maximize representativeness, we adopted provider-mediated community-based recruitment. Discussion Through JECS, chemical substances to which children are exposed during the fetal stage or early childhood will be identified. The JECS results will be translated to better risk assessment and management to provide healthy environment for next generations.

The identification of thyroid cancers among children after the Chernobyl nuclear power plant accident propelled concerns regarding long-term radiation effects on thyroid cancer in children affected by the Fukushima Daiichi nuclear power plant accident in Fukushima, Japan. Herein we consider the potential association between absorbed dose in the thyroid and the risk of developing thyroid cancer as detected by ultrasonography on 300 473 children and adolescents aged 0–18 years in Fukushima. The absorbed dose mentioned in the present study indicates the sum of that from external exposure and that from internally deposited radionuclides. We grouped participants according to estimated absorbed doses in each of 59 municipalities in Fukushima Prefecture, based on The United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) 2013 report. The 59 municipalities were assigned to quartiles by dose. We limited our analyses to participants aged ≥6 years because only one case of thyroid cancer was observed in participants aged ≤5 years; 164 299 participants were included in the final analysis. Compared with the lowest dose quartile, the age- and sex-adjusted rate ratios (95% confidence intervals) for the low-middle, high-middle and highest quartiles were 2.00 (0.84–4.80), 1.34 (0.50–3.59) and 1.42 (0.55–3.67) for the 6–14-year-old groups and 1.99 (0.70–5.70), 0.54 (0.13–2.31) and 0.51 (0.12–2.15) for the >15-year-old group, respectively. No dose-dependent pattern emerged from the geographical distribution of absorbed doses by municipality, as estimated by UNSCEAR, and the detection of thyroid cancer among participants within 4–6 years after the accident. Ongoing surveillance might further clarify the effects of low-dose radiation exposure on thyroid cancer in Fukushima.

Background: After the first-round (Preliminary Baseline Survey) ultrasound-based examination for thyroid cancer in response to the accident at the Fukushima Daiichi Nuclear Power Plant in 2011, two rounds of surveys (Full-scale Survey) have been carried out in Fukushima Prefecture. Using the data from these surveys, the geographical distribution of thyroid cancer incidence over 6 or 7 years after the disaster was examined.Methods: Children and adolescents who underwent the ultrasound-based examinations in the second- and/or third-round (Full-scale) survey in addition to the first-round survey were included. With a discrete survival model, we computed age, sex, and body mass index standardized incidence ratios (SIRs) for municipalities. Then, we employed spatial statistics to assess geographic clustering tendency in SIRs and Poisson regression to assess the association of SIRs with the municipal average absorbed dose to the thyroid gland at the 59-municipality level.Results: Throughout the second- and third-round surveys, 99 thyroid cancer cases were diagnosed in the study population of 252,502 individuals. Both flexibly shaped spatial scan statistics and maximized excess events test did not detect statistically significant spatial clustering (P = 0.17 and 0.54, respectively). Poisson regression showed no significant dose-response relationship: the estimated relative risks of lowest, middle-low, middle-high, and highest areas were 1.16 (95% confidence interval [CI], 0.52–2.59), 0.55 (95% CI, 0.31–0.97), 1.05 (95% CI, 0.79–1.40), and 1.24 (95% CI, 0.89–1.74).Conclusion: There was no statistical support for geographic clustering or regional association with radiation dose measures of the thyroid cancer incidence in the cohort followed up to the third-round survey (fiscal years 2016–2017) in Fukushima Prefecture.

Abstract Context Examining how overweight/obesity impacts thyroid nodule development in children and adolescents by sex and age allows speculation on the mechanism. Objective We examined whether overweight/obesity in children and adolescents is associated with thyroid nodule development by sex and age. Methods Approximately 300 000 participants who underwent thyroid ultrasonography in the Fukushima Health Management Survey after a nuclear accident were enrolled. Those without nodules in the initial 2 examinations (1-3 and 4-5 years postaccident) were prospectively assessed for nodule development in the third examination (6-7 years postaccident) relative to baseline overweight status, with an average follow-up of 4.2 years. This was a population-based prospective cohort study. The first and second thyroid examinations involved 299 939 and 237 691 participants, respectively, excluding those with thyroid nodules. After the third examination, 184 519 participants were finalized for analysis. Multivariable adjusted odds ratios of new detected thyroid nodules for overweight participants were compared with normal-weight participants. Results New thyroid nodules were detected in 660 participants. Being overweight was positively associated with thyroid nodules. The adjusted odds ratio (95% CI) of thyroid nodules for overweight participants compared with other participants was 1.27 (1.04-1.57). Additionally, the multivariable adjusted odds ratios for overweight males and females were 1.21 and 1.32, respectively, and those for different age groups (0-9, 10-14, and 15-19 years) ranged from 1.17 to 1.75. Conclusion Being overweight was associated with thyroid nodules in children and adolescents, mostly adolescent females, regardless of their proximity to the nuclear power plant.

In response to concerns about health due to radiation exposure, the Fukushima Prefecture launched the Thyroid Ultrasound Examination program for residents aged 0–18 years at the time of the earthquake. Herein, we considered the confounding factors involved in the regional differences in the development of thyroid cancer. In this study, the 242 065 individuals who participated in both first- and second-round surveys were classified into four groups by address according to their air radiation dose. The number of participants diagnosed as malignant or suspicious for malignancy by cytological examination were 17, 38, 10 and 4 with detection rates of 53.8, 27.8, 21.7 and 14.5 per 100 000 participants in Regions 1, 2, 3 and 4, respectively. Sex (P = 0.0400), age at the time of the primary examination (P < 0.0001) and interval between the first- and second-round surveys (P < 0.0001) were significantly different among the four regions, and these were suspected to be confounding factors affecting regional differences in malignant nodule detection rates. In addition, significant regional differences were observed in the participation rate in the confirmatory examination (P = 0.0037) and the fine needle aspiration cytology implementation rate (P = 0.0037), which could be potential biases. No significant regional differences in the detection of malignant nodules were found in the multivariate logistic regression analysis after adjusting for the survey interval alone or for sex, age and survey interval. The confounding factors and biases identified in this study that may have important impacts on thyroid cancer detection rate should be fully considered in future studies.

BackgroundJapan, which currently maintains the highest life expectancy in the world and has experienced an impressive gain in adult height over the past century, has suffered a dramatic twofold increase in low birth weight (LBW) births since the 1970s.MethodsWe observed secular trends in birth characteristics using 64 115 249 live births included the vital statistics (1969–2014), as well as trends in average height among 3 145 521 adults born between 1969 and 1996, included in 79 surveys conducted among a national, subnational or community population in Japan.ResultsLBW rates exhibited a U-shaped pattern showing reductions until 1978–1979 (5.5%), after which it increased. Conversely, average adult height peaked for those born during the same period (men, 171.5 cm; women, 158.5 cm), followed by a reduction over the next 20 years. LBW rate and adult height showed a strong inverse correlation (men, r=−0.98; women, r=−0.88). A prediction model based on birth and economical characteristics estimated the national average of adult height would continue to decline, to 170.0cm (95% CI 169.6 to 170.3) for men and 157.9cm (95% CI 157.5 to 158.3) for women among those born in 2014.ConclusionsAdult height in Japan has started to decline for those born after 1980, a trend that may be attributed to increases in LBW births over time. Considering the known association between shorter adult height and adverse health outcomes, evidence of population-level decline in adult health due to long-term consequences of increasing LBW births in Japan is anticipated.

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.

BackgroundIn October 2011, the Fukushima prefectural government started a thyroid ultrasound examination (TUE) as part of the Fukushima Health Management Survey following the Fukushima Daiichi Nuclear Power Plant accident. The proportion of examinees is an important factor when interpreting the results.ObjectivesTo construct models that assess the relationship between the proportion of non-examinees and the characteristics of eligible participants in the first-round to third-round TUEs. Using these models, estimate the number of thyroid cancer cases in the entire population for each survey, considering non-examinees.DesignModel-based estimation using cohort survey data.SettingsFukushima Health Management Survey from 2011 to 2017.ParticipantsChildren and adolescents aged 18 years or younger (363 342 individuals) who were identified through resident registration records, resided in Fukushima Prefecture at the time of the accident, and were eligible for each TUE.Outcome measuresModelling the relationship between non-examinee status and individual characteristics, and estimating the number of cases in the entire population for each survey round.ResultsThe area under the receiver operating characteristic curve of the constructed models ranged from 0.815 to 0.905. In the first-round, second-round and third-round TUEs, 115, 70 and 30 cases were observed among 294 921, 258 771 and 208 955 examinees, respectively, whereas the estimated number of cases in the entire population including the non-examinees was 177.3 (95% CI 167.0 to 188.0), 126.3 (95% CI 106.3 to 150.2) and 49.7 (95% CI 35.8 to 71.9), respectively.ConclusionsThese estimates were higher than the actual number of observed cases because they considered non-examinees. Our model for non-examination showed a high discriminant accuracy and was considered to capture well the factors that resulted in non-examinees. This study’s findings provide valuable information for studies considering the number of potential thyroid cancer cases among non-examinees and may facilitate appropriate interpretation of reports and prospective survey outcome management.