Otake M, Schull W J
RERF Department of Statistics, School of Public Health, University of Texas Health Science Center, Houston.
Int J Radiat Biol. 1993 Feb;63(2):255-70. doi: 10.1080/09553009314550341.
Of 1566 individuals prenatally exposed to the atomic bombings of Hiroshima and Nagasaki, 1473 had the circumference of their head measured at least once between ages 9 and 19. Among these 1473 individuals, 62 had small heads--the circumference of the heads was two standard deviations or more below the observed specific-age-at measurement mean. Of 26 cases with severe mental retardation, 15 (58%) had small heads. Most (86%) of the individuals with small heads were exposed in the first trimester (about < 12 weeks postovulation) or second trimester (about 12-24 weeks postovulation)--55% in the former period and 31% in the latter. Various dose-response relationships, with and without a threshold, have been fitted to the data grouped by the trimester or postovulatory age (weeks after ovulation) at which exposure occurred. A significant effect of radiation on the frequency of individuals with atypically small heads is observed only in the first and second trimesters and for the intervals postovulation of 0-7 weeks and 8-15 weeks. Although the risk of a small head at 0-7 weeks postovulation increases significantly with increasing dose, no increase in risk for severe mental retardation is noted in this period. No excess risk of a small head was seen in the third trimester (about > or = 25 weeks postovulation) or among individuals exposed at 16 weeks or more postovulation. The mean IQ values of mentally retarded cases with and without small heads were 63.8 and 68.9, respectively. No significant difference exists between these two IQ means, but both were significantly smaller than 96.4, the IQ value for individuals with small heads without severe mental retardation and 107.8, the value for the overall sample.
在1566名在广岛和长崎原子弹爆炸时处于孕期的个体中，1473人在9至19岁之间至少测量过一次头围。在这1473名个体中，62人头部较小——其头围比特定测量年龄时观察到的平均值低两个标准差或更多。在26例重度智力发育迟缓病例中，15例（58%）头部较小。大多数（86%）头部较小的个体在孕早期（排卵后约<12周）或孕中期（排卵后约12 - 24周）受到辐射——前者占55%，后者占31%。已将有无阈值的各种剂量反应关系拟合到按暴露发生时的孕期或排卵后年龄（排卵后周数）分组的数据中。仅在孕早期和孕中期以及排卵后0 - 7周和8 - 15周的时间段内观察到辐射对非典型小头个体频率有显著影响。虽然排卵后0 - 7周小头风险随剂量增加而显著增加，但在此期间未观察到重度智力发育迟缓风险增加。在孕晚期（排卵后约≥25周）或排卵后16周及以上受辐射的个体中未发现小头风险增加。有小头和无小头的智力发育迟缓病例的平均智商值分别为63.8和68.9。这两个智商平均值之间无显著差异，但均显著低于无重度智力发育迟缓的小头个体的智商值96.4以及总体样本的智商值107.8。
