(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
“>