UCL in the News: Study reveals how having an older brother can make you shorter

David Lawson, an anthropologist, working at UCL, found that when other socioeconomic factors were taken into account, children's height was strongly dependent on the number of their older siblings.

Scientists had followed children born to nearly 14,000 families in the 1990s, who had enrolled on the Avon Longitudinal Study of Parents and Children, one of the largest public health studies in Britain. …

In a family of four children, the siblings were 2.5cm shorter than average. The youngest child was most affected.

The study found that while having older siblings of either sex affected a younger child's development, the effect of older sisters was more mild. …

Mr Lawson urged caution in interpreting the results, not yet published. But if the findings are confirmed, they will add to a growing body of work that suggests younger siblings fare less well in life, often because they have poorer nutrition and do not perform so well at school. …

"What's unexpected is that we see this even in a rich, western population," Mr Lawson told the British Association festival of science in York: "All else being equal, growth is significantly retarded by the presence of siblings. Older siblings are associated with relatively higher costs than younger siblings, and in most cases, brothers represent a larger threat to development than sisters." …

Ian Sample, 'The Guardian'