STUDY:

JOURNAL: BMJ. 2004;328:19-21

AUTHORS: Per Hall

ABSTRACT: Infants exposed to doses of ionizing radiation equivalent to a computed tomography (CT) scan have lower cognitive abilities as adults.

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COMMENTARY: "Ionising radiation may impair the developing human brain and adversely affect cognitive processes," write Per Hall, from Karolinska Institute in Stockholm, Sweden, and colleagues. "CT scanning, which delivers high doses of ionising radiation, is increasingly being used in young children after minor head trauma."

The study cohort consisted of 3,094 men who had received radiation therapy during the period from 1930 to 1959, before they were 18 months of age. At age 18 or 19 years, psychological testing revealed a negative dose-response relationship for three cognitive tests for learning ability and logical reasoning, but not for spatial recognition.

The proportion of boys who attended high school decreased with increasing doses of ionizing radiation to both frontal and posterior brain regions, from 32% for no radiation exposure to 17% for exposure greater than 250 mGy. With frontal radiation, the multivariate odds ratio for high school attendance was 0.47 (95% confidence interval [CI], 0.26 - 0.85; P = .0003 for trend), and with posterior radiation it was 0.59 (95% CI, 0.23 - 1.47; P = .0005).

"Irradiation of the brain with dose levels overlapping those imparted by CT can, in at least some instances, adversely affect intellectual development when the infant brain is exposed to ionising radiation at doses equivalent to CT scans of the skull," the authors write. "The risk and benefits of CT scans in minor head trauma need re-evaluating."

The European Commission supported this study, and the authors report no conflicts of interest.