(Ener Atoll of Reeidence Rongelap Persons Alive in 1954 Mean Age, y Solltary Previous Total Crude Adjcsted Females, % Nodules Thyroidectomy* Nodules Prevalence, % Prevalence, % “ 45.9 47.4 56.7 54.5 0 17 17 38.6 37.2 Meiit Island 167 46.2 48 3 1 4 24 24 Ailuk 177 45.6 58.0 7 1 Utrik 67 167 Likiep 161 Wotje 47.7 53.8 47.8 48.7 1 5 6 9.0 10.3 49 4.5 8 12 2 14 5.4 8.7 9 5 14 8.7 9.6 183 46.5 53.5 7 2 9 49 4? Lae 66 48.4 48.4 6 1 7 10.6 10.2 Ujae 108 46.5 59.6 7 3 10 9.3 9.8 3 48 66.7 1 1 2 8.0 313 48.6 Maloelap Wotho Kwajalein 428 Ebon ME Jah Tots 9.8 51.4 49.8 13 12 25 259 45.4 60.1 5 3 & i 3.2 Ww a72 55.6 1 0 1 0.9 0.8 2273 46.8 55.0 a7 35 142 6.2 5.7 50.2 15 2 5.9 17 5.3 5.4 5.2 *Excludes five subjects in whom the pathologic findings indicated normal thyroid disease. Table 4.—Pradictors of Rlsk for Thyroid Nodules Thyroid Carcinome Logistic Regression Analysis Variable Conatent Age Sext Distance 6 Distance x @ Coefficient - 1,872 0.01914° 1.313$ —0.01008¢ =0.05312$ 0.0001457$ $2 0.8310 0.0062 0.2180 0.0021 0.0132 0.00004 Odds Ratio (95% Confidence intervals) Les 1.21/10 y (1.07/10 y — 1.37/10 y) 3.72 FM (2.42~5.70 F/M) 0.33/100 miles (0.22/100 miles ~ 0.50/100 miles) 0.59710" (0.48/10" 0.78/10) 1. 16/100 miles x 10° (1.07/100 miles x 10°1,25/100 miles x 10) *P = 003. TMale =1 and female = 2. +P<.001. The prevalence of solitary thyroid nodules was the outcomevariable in this study. Because many individuals with new thyroid nodules were treated medi- cally rather than referred for surgery, ascertainment ofthyroid carcinoma was incomplete in this study cohort. How- ever, since previous authors have pro- vided absolute risk estimates for total thyroid nodules as well as for thyroid carcinoma, our risk estimates for total thyroid nodules in this study can be directly compared.” Data Collection The term thyroid nodule does not connote the histologic characteristics of a lesion. We use the terms thyroid neoplasia and thyroid nodule synonymously in this article to indicate that such lesions may be either malignant or benign. Because the hypothesis of this study pertains strictly to solitary thyroid nodules, individuals with Graves’ disease, multinodular goiter, or simple diffuse goiter were not classified as having nod- ules for the purpose of this analysis. Individuals whose 1954 residence was not one of the 14 study atolls were excluded altogether from the preva- lence data. Previous Thyroidectomy Almostall individuals from Rongelap and Utrik in whom thyroid nodules developed had had thyroid surgery, gener- ally in the United States under the direction of Brookhaven National Laboratory, Upton, NY.” This is also true for certain individuals in the comparison groups. The majority of the atoll popula632 JAMA, Aug 7, 1987—Vo!l 258, No. 5 -* tions, however, had had little access to physicians. As a result, most thyroid nodules in this study were newly diagnosed. Because cohort attrition from thyroid mortality is extremely low and because nodules generally do not spon- taneously regress, we decided to count individuals with previous thyroidectomy as having had a thyroid nodule if the indication for surgery was the re- moval of a thyroid nodule. For Marshall Islanders with prior thyroidectomy, the indication for the surgery was ascertained from available medical records. The histologic characteristics of these malignant and benign neoplasms have been described previously.’ Individu- als with previous thyroid surgery for Graves disease, simple goiter, or indications other than a thyroid nodule were notclassified as having a thyroid nodule in this analysis. Individuals whose surgical histologic findings were “normal thyroid tissue” were also not classified as having nodules. The net result of these classifications is that the preva- lence data reported here are thought to approximate closely the cumulative incidence of thyroid nodularity since 1954. A physical examination of the thyroid gland was carefully performed by one of us (T.E.H.) on all 7266 study parti- cipants. Detailed drawings and expla- nations were recorded for all thyroid abnormalities, including evidence of previous thyroid surgery. Nodules were described by location, consistency, contour, discreteness, and size. In addition to demographic information the following information was also obtained: a brief medical and surgical history, blood pressure, pulse, ‘and examination of the cervical lymph nodes. Residence location in 1954 was recorded. Persons with thyroid abnormalities were referred for a comprehensive medical evaluation in the author's (T.E.H.) central office on Majuro Atoll. The same qualified Marshallese interpreter was presentat all screening examinations. Travel to the 14 atolls and islands within atolls was accomplished by airplane, ship, small craft, and outrigger canoe. To diminish observer bias, the thyroid examiner was masked to the history of exposure: the Marshallese interpreter asked each person about his or Thyroid Neoplasia—Hamilton et al “>