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