Size at birth and motor activity during stress in children aged 7-9 years

Schlotz, Wolff, Jones, Alexander, Phillips, Naomi M.M., Godfrey, Keith M. and Phillips, David I.W. (2007) Size at birth and motor activity during stress in children aged 7-9 years. Pediatrics, 120 (5), e1237-e1244. (doi:10.1542/peds.2006-3277).

Abstract

Objective: Small size at birth is linked with metabolic and cardiovascular disease. There is increasing evidence that it is also linked with physiological stress responses and abnormal behaviour, in particular symptoms of hyperactivity. We therefore investigated associations between size at birth and motor activity during psychosocial stress.
Methods: In 123 children aged 7-9 years, we examined the relations of birth weight, head circumference, length and ponderal index at birth with motor activity upon exposure to both stress and non-stress situations. Videos were recorded while the children performed a story and a maths task in front of an audience (stress) and watched a movie (non-stress); motor activity was defined as lifting or tilting of a foot.
Results: Children who had had a smaller head circumference at birth demonstrated greater motor activity during the stress test. There were marked gender differences in the results. In boys, lower birth weight, head circumference and ponderal index were associated with greater motor activity during the stress test, but not associated with motor activity during the non-stress situation. The findings remained significant when potential confounding variables were controlled for. There were no associations in girls.
Conclusions: The findings suggest long-term effects of an adverse fetal environment on the behavioural stress response in boys, and parallel similar sex-specific effects on different stress response systems in humans and animals. The results could reflect permanent alterations of dopaminergic neurotransmission and have implications for the etiology of clinical hyperactivity.

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Contributors

Author: Keith M. Godfrey

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