New York - Head growth in foetal life and infancy is associated with later intelligence, new research hints. Moreover, catch-up increases do not appear to compensate for poor early growth.
"Brain growth in early life may be important in determining not only the level of peak cognitive function attained but also whether such function is preserved in old age," the study team writes in the journal Pediatrics.
"Older people with a larger head circumference tend to perform better on tests of cognitive function and may have reduced risks of cognitive decline and of Alzheimer's disease."
Several studies in children have shown that those with larger brains, measured with imaging studies or as head circumference, tend to score higher on tests of cognitive function. Similar associations have been found in adults.
For their study, Dr Catharine Gale, of the University of Southampton, United Kingdom, and colleagues examined the effect of head growth in foetal life, infancy, and childhood on brain power at the ages of four and eight years. Included in the study were 633 term children who had their head circumference measured at birth and at regular intervals thereafter.
By age one, mean head circumference increased from 34,9cm at birth to 46,6cm. Head growth after infancy was slower. Mean head circumference increased to 50,9cm by four years and to 53,4cm by 8 years.
Average full-scale IQ was 106,3 at four years and 105,6 at eight years. The investigators report that only prenatal growth and growth during infancy were associated with later IQ.
At four years, after adjusting for parental factors, there was an average increase in full-scale IQ of 2,41 points for each one standard deviation increase in head circumference at birth and 1,97 points for each 1-SD increase in head growth during infancy. This was conditional on head size at birth.
Head circumference at birth was no longer associated with IQ at eight years. However, head growth during infancy remained significantly predictive, with full-scale IQ increasing an average of 1,56 points for each 1-SD increase in head growth.
SOURCE: Pediatrics October 2006.