Table 3.— DescriptiveStatistics of 1954 Cohort and Prevalence of Thyroid Nodularity Sa Atoll of Persons Residence Rongelap Alive In 1954 44 Utrik Mean Age, y 45.9 Females, % 54.5 Solitary Nodules 0 Previous Thyroidectomy* 17 Total Nodules 17 Crude AgeAdjusted Prevalence, % 38.6 Prevalence, % 37.2 67 474 56.7 1 5 6 9.0 10.3 Mojit Island 167 46.2 54.8 3 1 4 2.4 2.4 Alluk V7 456 58.0 7 1 8 4.5 4.9 Likiep 167 47.7 53.6 12: 2 14 6.4 8,7 Wotle 161 47.8 48.7 9 5 14 8.7 9.6 Lae 66 48.4 48.4 6 1 7 10.6 10.2 Ujae 108 46.5 59.6 7 3 10 2 44.8 66.7 t 1 2 8.0 5.8 Kwajalein 425 51.4 49.6 13 12 25 5.9 - 63 Jaluit 313 48.6 §9.2 15 2 17 5.4 5.2 Ebon 259 45.4 60.1 5 3 8 3.1 3.2 Total 2273 48.8 55.0 8? 55 142 6.2 5.7 Maioelap 183 Wotho Mii W1 46.5 53.5 47.2 55.6 7 1 2 0 9 49 4.7 93 1 0.9 9.6 0.8 *Excludes five subjects in whom the pathologic findings indicated normal thyroid disease. Table 4.—Predictors of Risk for Thyroid Nodules Thyroid Carclnoma Logistic Regression Analysis Regression Variabie Constant Age Sext Distance 8 Distance x 6 ‘ Coefficient — 1.872 SE 0.6310 Odds Ratio (95% Confidence intervals) eee 0.01914" 0.0062 1.21/10 y (1.07/10 y ~ 1.37/10 y) 1.313¢ - 0.010984 —0,05312¢ 0,0001457$ 0.2180 0.0021 0.0132 0.00004 3.72 Fé (2.42 — 5.70 F/M) 0.34/100 miles (0.22/100 miles — 0.50/100 miles) 0.59/t0° (0.45/10° — 0.76/10 1.16/100 miles x 10° (1.07/100 miles x 10°- 1,25/100 miles x 10°) The prevalence of solitary thyroid nodules was the outcomevariable in this study. Because manyindividuals with new thyroid nodules were treated medically rather than referred for surgery, ascertainment of thyroid 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.” *P = 003. tMale=1 and female = 2. tP<.001. Data Collection nodules less than 1 cm were classified as normal! thyroid examination results. 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 notclassified as having nodules for the purpose of this analysis. Individuals whose 1954 residence was not one of the 14 study atolls were excluded altogether from the prevalence data. Previous Thyroidectomy Almostall individuals from Rongelap and Utrik in whom thyroid nodules developed had had thyroid surgery, generally in the United States under the direction of Brookhaven National Laboratory, Upton, NY.’ Thisis also true for certain individuals in the comparison groups. The majority ofthe atoll popula632 JAMA,Aug 7, 1987—Vol 258, No. 5 tions, however, had hadlittle 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 spontaneously regress, we decided to count individuals with previous thyroidectomy as having had a thyroid nodule if the indication for surgery was the removal 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.” Individuals with previous thyroid surgery for Graves’ disease, simple goiter, or indications other than a thyroid nodule were not classified 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 prevalence data reported here are thought to approximate closely the cumulative incidence of thyroid nodularity since 1954. A physical examinationof the thyroid gland was carefully performed by oneof us (T.E.H.) on all 7266 study participants. Detailed drawings and explanations were recorded for all thyroid abnormalities, including evidence of previous thyroid surgery. Nodules were described by location, consistency, con- tour, disereteness, 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 tothe history of exposure: the Marshalleseinterpreter asked each person about his or Thyroid Neoplasia—Hamilton et al he