Table 1.
Characteristics of explanatory variables of eligible people.
| Substituted Dataa (Dataset A) N = 253346 |
Complete Datab (Dataset B) N = 113120 |
|||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| N | Detected suspected thyroid cancer cases (DSTC cases) | Total person-years (PY)c | DRd(per 105 PY) | DRRe | DRR 95% CIf |
N | Detected suspected thyroid cancer cases (DSTC cases) | Total person-years (PY) | DR (per 105 PY) | DRR | DRR 95% CI |
|
| All | 253346 | 97 | 939207.2 | 10.328 | – | – | 113120 | 46 | 422682.3 | 10.883 | – | – |
| Missing | 0 | 0 | – | – | – | – | 0 | 0 | – | – | – | – |
| External radiation exposure (mSv) 10 levels | ||||||||||||
| [0,1)g (reference) | 132083 | 47 | 490257.8 | 9.587 | 1 | – | 65444 | 21 | 242228.4 | 8.670 | 1 | – |
| [1,2) | 111269 | 45 | 410434.4 | 10.964 | 1.146 | 0.762–1.725 | 37682 | 20 | 141938.9 | 14.091 | 1.634 | 0.886–3.014 |
| [2,3) | 9552 | 5 | 36722.0 | 13.616 | 1.418 | 0.564–3.565 | 9552 | 5 | 36722.0 | 13.616 | 1.565 | 0.590–4.150 |
| [3,4) | 360 | 0 | 1458.0 | 0 | – | – | 360 | 0 | 1458.0 | 0 | – | – |
| [4,5) | 44 | 0 | 174.5 | 0 | – | – | 44 | 0 | 174.5 | 0 | – | – |
| [5,6) | 22 | 0 | 93.2 | 0 | – | – | 22 | 0 | 93.2 | 0 | – | – |
| [6,7) | 5 | 0 | 22.2 | 0 | – | – | 5 | 0 | 22.2 | 0 | – | – |
| [7,8) | 5 | 0 | 20.8 | 0 | – | – | 5 | 0 | 20.8 | 0 | – | – |
| [8,9) | 6 | 0 | 24.2 | 0 | – | – | 6 | 0 | 24.2 | 0 | – | – |
| [9,∞) | 0 | 0 | – | – | – | – | 0 | 0 | 0 | 0 | – | – |
| External radiation exposure (mSv) 2 levels | ||||||||||||
| <1 (reference) | 132083 | 47 | 490257.8 | 9.587 | 1 | – | 65444 | 21 | 242228.4 | 8.670 | 1 | – |
| 1+ | 121263 | 50 | 448949.3 | 11.137 | 1.164 | 0.782–1.734 | 47676 | 25 | 180453.8 | 13.854 | 1.603 | 0.898–2.864 |
| Missing | 0 | 0 | – | – | – | – | 0 | 0 | – | – | – | – |
| Sex | ||||||||||||
| Boy (reference) | 127373 | 41 | 471312.4 | 8.699 | 1 | – | 56739 | 22 | 211581.9 | 10.398 | 1 | – |
| Girl | 125973 | 56 | 467894.7 | 11.969 | 1.381 | 0.923–2.065 | 56381 | 24 | 211100.3 | 11.369 | 1.098 | 0.616–1.958 |
| Missing | 0 | 0 | – | – | – | – | 0 | 0 | – | – | – | – |
| Age (years) | ||||||||||||
| [3,9)e | 62126 | 0 | 246577.7 | 0 | – | – | 30870 | 0 | 122925.4 | 0 | – | – |
| [9,12) (reference) | 49500 | 10 | 201164.8 | 4.971 | 1 | – | 21289 | 4 | 86988.0 | 4.598 | 1 | – |
| [12,15) | 52849 | 24 | 208325.8 | 11.520 | 2.318 | 1.108–4.846 | 21872 | 8 | 87204.7 | 9.174 | 1.995 | 0.601–6.626 |
| [15,18) | 50091 | 31 | 162664.8 | 19.058 | 3.834 | 1.880–7.820 | 20558 | 14 | 68939.1 | 20.308 | 4.416 | 1.454–13.417 |
| [18,25) | 28456 | 30 | 79000.9 | 37.974 | 8.764 | 4.285–17.928 | 15133 | 20 | 43103.0 | 46.401 | 11.601 | 3.965–33.941 |
| [25,∞) | 1 | 0 | – | – | – | – | 1 | 0 | – | – | – | – |
| Missing | 10323 | 2 | – | – | – | – | 3397 | 0 | – | – | – | – |
| Past medical history (PMH) | ||||||||||||
| No (reference) | 217523 | 78 | 805981.7 | 9.678 | 1 | – | 96528 | 37 | 360193.5 | 10.272 | 1 | – |
| Yes | 33098 | 18 | 124004.2 | 14.516 | 1.502 | 0.899–2.507 | 15638 | 9 | 59158.4 | 15.213 | 1.482 | 0.715–3.071 |
| Missing | 2725 | 1 | – | – | – | – | 954 | 0 | – | – | – | – |
| Family history of thyroid cancer (FTC) | ||||||||||||
| No (reference) | 231142 | 90 | 856918.5 | 10.503 | 1 | – | 102612 | 41 | 383311.9 | 10.696 | 1 | – |
| Yes | 19724 | 7 | 73923.2 | 9.469 | 0.903 | 0.418–1.948 | 9664 | 5 | 36437.9 | 13.722 | 1.282 | 0.506–3.243 |
| Missing | 2480 | 0 | – | – | – | – | 844 | 0 | – | – | – | – |
| Frequency of eating seafood (FESF) | ||||||||||||
| 0 or 1–2/week (reference) | 186784 | 73 | 690049.7 | 10.579 | 1 | – | 82597 | 35 | 307152.9 | 11.395 | 1 | – |
| 3－5 or 6–7/week | 64061 | 24 | 240778.9 | 9.968 | 0.938 | 0.591–1.487 | 29728 | 11 | 112797.9 | 9.752 | 0.851 | 0.432–1.675 |
| Missing | 2501 | 0 | – | – | – | – | 795 | 0 | – | – | – | – |
| Frequency of eating seaweed (FESW) | ||||||||||||
| 0 or 1–2/week (reference) | 198713 | 79 | 735371.2 | 10.743 | 1 | – | 87747 | 35 | 326777.2 | 10.711 | 1 | – |
| 3－5 or 6–7/week | 51334 | 18 | 192566.8 | 9.347 | 0.867 | 0.519–1.446 | 24260 | 11 | 91994.3 | 11.957 | 1.110 | 0.564–2.186 |
| Missing | 3299 | 0 | – | – | – | – | 1113 | 0 | – | – | – | – |
| Six districts | ||||||||||||
| North (reference) | 66729 | 29 | 252114.4 | 11.503 | 1 | – | 32209 | 18 | 123046.1 | 14.629 | 1 | – |
| Central | 70545 | 23 | 253836.0 | 9.061 | 0.786 | 0.455–1.358 | 31478 | 9 | 114408.8 | 7.867 | 0.537 | 0.241–1.195 |
| South | 20328 | 5 | 72802.6 | 6.868 | 0.594 | 0.230–1.535 | 8735 | 2 | 31510.7 | 6.347 | 0.432 | 0.100–1.863 |
| Soso | 23103 | 12 | 94917.9 | 12.643 | 1.102 | 0.562–2.159 | 10507 | 8 | 43699.2 | 18.307 | 1.256 | 0.546–2.888 |
| Iwaki | 42948 | 19 | 167604.4 | 11.336 | 0.984 | 0.552–1.754 | 16547 | 5 | 64954.1 | 7.698 | 0.527 | 0.196–1.418 |
| Aizu + Minami Aizu | 29693 | 9 | 97931.8 | 9.190 | 0.793 | 0.376–1.676 | 13644 | 4 | 45063.3 | 8.876 | 0.604 | 0.204–1.783 |
| Missing | 0 | 0 | – | – | – | – | 0 | 0 | – | – | – | – |
| Overweight | ||||||||||||
| No (reference) | 197230 | 69 | 729686.0 | 9.456 | 1 | – | 89570 | 34 | 333876.8 | 10.183 | 1 | – |
| Yes | 52286 | 26 | 195554.6 | 13.296 | 1.397 | 0.890–2.194 | 22422 | 11 | 84629.8 | 12.998 | 1.267 | 0.642–2.501 |
| Missing | 3830 | 2 | – | – | – | – | 1128 | 1 | – | – | – | – |
a
Dataset A：for cases in which missing external radiation-dose data were substituted by the median dose of 6 districts in which each resident was at the accident.
b
Dataset B：for cases in which external radiation-dose data were observed.
c
PY: person-years.
d
DR: detection rate per 105 people.
e
DRR: detection rate ratio.
f
95% CI: 95% Confidence Interval.
g
[a,b): the interval with greater than or equal to a and less than b.