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Purpose: Long-term follow-up studies sometimes rely on retrospective identification of the cohort to be followed. Few such studies have been conducted, however, that rely on very old source records, perhaps because of concern that identification and location of a cohort based on very old records would not be feasible., Methods: The Hanford Thyroid Disease Study (HTDS), conducted in the 1990s, identified 5199 cohort members using Washington state birth records from 1940-1946. The limited information contained therein was used to trace cohort members to the present day, nearly 50 years later., Results: We found the best strategy to locate individuals efficiently is to use a combination of methods and resources in a phased approach, beginning with readily available and easy-to-use sources of information before employing more time-intensive strategies that are costly and rely on information that is difficult to obtain. Motor vehicle licensing records and directories were the most useful individual sources of information. Using this approach, the HTDS successfully located 94% of the 5199 cohort members identified., Conclusions: It is feasible to successfully trace and locate a very high proportion of individuals identified from very old records that contain little information.

Context: The risk of primary hyperparathyroidism from exposure to external radiation has been well documented in the last 20 yr. However, it remains unclear whether hyperparathyroidism might also be caused by internal exposure to radioactive iodine., Objective: The objective of this study was to determine whether exposure to 131I from the Hanford Nuclear Site during 1944-1957 increased the risk of hyperparathyroidism among people living in the area., Design: The Hanford Thyroid Disease Study was conducted as a retrospective cohort study., Setting: The study setting was the general community in Washington State., Participants: The participants were 5199 persons born to mothers with usual residence in one of seven counties in eastern Washington State, randomly selected from birth records for the years 1940-1946., Intervention: Of the 5199 selected, 3440 underwent a Hanford Thyroid Disease Study clinical evaluation, including an evaluation for hyperparathyroidism. Individual thyroid radiation dose, which could be estimated for 3191 study participants, ranged from 0.0029-2823 mGy (mean, 174 mGy)., Main Outcome Measure: Hyperparathyroidism was the main outcome measure., Results: Of 3440 evaluable participants, we confirmed 12 cases of primary hyperparathyroidism (0.35%). We found no evidence that the cumulative incidence of hyperparathyroidism increased with increasing radiation dose., Conclusion: In summary, this study shows no evidence that 131I, received at young ages and at the doses and exposure conditions experienced by this cohort, increased the risk of primary hyperparathyroidism. However, the effects of different doses and conditions of exposure to 131I on the risk of hyperparathyroidism remain to be defined.

Context: Approximately 740,000 Ci (2.73 x 10(16) Bq) of iodine 131 (131I) were released to the atmosphere from the Hanford Nuclear Site in Washington State from 1944 through 1957. The risk of thyroid disease resulting from prolonged environmental 131I exposure is poorly understood., Objective: The Hanford Thyroid Disease Study (HTDS) was conducted to determine if thyroid disease is increased among persons exposed as children to atmospheric releases of 131I from Hanford., Design: Retrospective cohort study. Exposure could have occurred from December 1944 through 1957. Follow-up occurred until the time of the HTDS examination (December 1992-September 1997). Participants' thyroid radiation doses from Hanford's 131I releases were estimated from interview data regarding residence and dietary histories., Setting: The cohort included a sample of all births from 1940 through 1946 to mothers with usual residence in 1 of 7 counties in eastern Washington State., Participants: Of 5199 individuals identified, 4350 were located alive and 3440 were evaluable; ie, had sufficient data for dose estimation and received an HTDS evaluation for thyroid disease, including a thyroid ultrasound, physical examination, and fine needle biopsy if required to evaluate thyroid nodularity., Main Outcome Measures: Thyroid cancer, benign thyroid nodules, total neoplasia, any thyroid nodules, autoimmune thyroiditis, and hypothyroidism., Results: There was no evidence of a relationship between Hanford radiation dose and the cumulative incidence of any of the outcomes. These results remained unchanged after taking into account several factors that might confound the relationship between radiation dose and the outcomes of interest., Conclusion: These results do not support the hypothesis that exposure during infancy and childhood to 131I at the dose levels (median, 97 mGy; mean, 174 mGy) and exposure circumstances experienced by our study participants increases the risk of the forms of thyroid disease evaluated in this study.

Residents of eastern Washington, northeastern Oregon, and western Idaho were exposed to I released into the atmosphere from operations at the Hanford Nuclear Site from 1944 through 1972, especially in the late 1940's and early 1950's. This paper describes the estimated doses to the thyroid glands of the 3,440 evaluable participants in the Hanford Thyroid Disease Study, which investigated whether thyroid morbidity was increased in people exposed to radioactive iodine from Hanford during 1944-1957. The participants were born during 1940-1946 to mothers living in Benton, Franklin, Walla Walla, Adams, Okanogan, Ferry, or Stevens Counties in Washington State. Whenever possible someone with direct knowledge of the participant's early life (preferably the participant's mother) was interviewed about the participant's individual dose-determining characteristics (residence history, sources and quantities of food, milk, and milk products consumed, production and processing techniques for home-grown food and milk products). Default information was used if no interview respondent was available. Thyroid doses were estimated using the computer program Calculation of Individual Doses from Environmental Radionuclides (CIDER) developed by the Hanford Environmental Dose Reconstruction Project. CIDER provided 100 sets of doses to represent uncertainty of the estimates. These sets were not generated independently for each participant, but reflected the effects of uncertainties in characteristics shared by participants. Estimated doses (medians of each participant's 100 realizations) ranged from 0.0029 mGy to 2823 mGy, with mean and median of 174 and 97 mGy, respectively. The distribution of estimated doses provided the Hanford Thyroid Disease Study with sufficient statistical power to test for dose-response relationships between thyroid outcomes and exposure to Hanford's I.