Technical Report No. 2-88
Effect on school performance of prenatal exposure to ionizing radiation in Hiroshima: A comparison of the T65DR and DS86 dosimetry systems
Otake M, Schull WJ, Fujikoshi Y, Yoshimaru HEditor’s note: A publication based on this report was published in Congenital Anomalies 29:309-20, 1989.
Summary
As a part of the continuing assessment of the effects on the developing embryonic and fetal brain of exposure to ionizing radiation, the school performances of prenatally exposed survivors of the atomic bombing of Hiroshima and a suitable comparison group have been studied. In this report, the changes in performance in seven school subjects according to dose are compared under the T65DR dosimetry heretofore used by ABCC-RERF, and the new dosimetry (DS86) installed in 1986.
Those survivors with school performance records but without T65DR doses, or not exposed in utero, or without school records are excluded. Thus, the T65DR study group consists of 1,090 children, including 14 clinically diagnosed cases of mental retardation. DS86 tissue doses are not yet available on 161 individuals, mostly those with T65DR doses less than 0.10 Gy. The DS86 sample thus involves 929 children (85.2%) of the T65DR study group and includes the same 14 severely mentally retarded persons.
The findings can be summarized as follows: Damage to the 8-15 week fetal brain appears to be linearly related to the fetal absorbed dose, as judged by the simple regression of average school performance score on dose. This is so for both the T65DR study group and the DS86 sample with or without the 14 cases of retardation. Damage to the fetus exposed at 16-25 weeks after fertilization appears similar to that seen in the 8-15 week group. Canonical and multiple correlations also show a highly significant relationship of exposure 8-15 weeks and 16-25 weeks after fertilization to achievement in school. This trend is stronger, however, in the earliest years of schooling. In the groups exposed with 0-7 weeks following fertilization, or 26 or more weeks after fertilization, there is no evidence of a radiation-related effect on scholastic performance. These results parallel those previously found in prenatally exposed survivors with respect to achievement in standard intelligence tests in childhood.
As a part of the continuing assessment of the effects on the developing embryonic and fetal brain of exposure to ionizing radiation, the school performances of prenatally exposed survivors of the atomic bombing of Hiroshima and a suitable comparison group have been studied. In this report, the changes in performance in seven school subjects according to dose are compared under the T65DR dosimetry heretofore used by ABCC-RERF, and the new dosimetry (DS86) installed in 1986.
Those survivors with school performance records but without T65DR doses, or not exposed in utero, or without school records are excluded. Thus, the T65DR study group consists of 1,090 children, including 14 clinically diagnosed cases of mental retardation. DS86 tissue doses are not yet available on 161 individuals, mostly those with T65DR doses less than 0.10 Gy. The DS86 sample thus involves 929 children (85.2%) of the T65DR study group and includes the same 14 severely mentally retarded persons.
The findings can be summarized as follows: Damage to the 8-15 week fetal brain appears to be linearly related to the fetal absorbed dose, as judged by the simple regression of average school performance score on dose. This is so for both the T65DR study group and the DS86 sample with or without the 14 cases of retardation. Damage to the fetus exposed at 16-25 weeks after fertilization appears similar to that seen in the 8-15 week group. Canonical and multiple correlations also show a highly significant relationship of exposure 8-15 weeks and 16-25 weeks after fertilization to achievement in school. This trend is stronger, however, in the earliest years of schooling. In the groups exposed with 0-7 weeks following fertilization, or 26 or more weeks after fertilization, there is no evidence of a radiation-related effect on scholastic performance. These results parallel those previously found in prenatally exposed survivors with respect to achievement in standard intelligence tests in childhood.