Genetics may influence age at which children first walk

Genetics may account for almost 25 percent of the variation in when children take their first steps, new evidence indicates.

A large-scale genome-wide association study (GWAS), led by the University of Surrey, investigated the genomes of over 70,000 infants aiming to identify genetic variants associated with the age a child begins walking. Researchers identified 11 genetic markers that can influence this development and concluded that genetics account for about a quarter of the variability between children.

'Until now, we didn't understand what causes the wide differences between children in when they take their first step,' said Dr Anna Gui, from Birkbeck, University of London, and first author of the paper, published in Nature Human Behaviour. 'Parents might often worry that walking early or late is a bad sign or that they have done something wrong. We see that genetics play a considerable role in influencing the timing of this milestone.'

The age at which children learn to walk is used clinically to monitor early development. First steps can occur within a wide window of 8-24 months however, UK clinical guidelines recommend consulting a paediatrician if a child is not walking by 15-18 months.

Understanding what causes variation in the age a child begins walking has wider implications, as it can inform governmental health policy on when, and how, children should be screened for developmental disorders. It can also illuminate the potential causes of this developmental milestone.

The study concluded that the age a child begins walking is not solely regulated by environmental factors, previously identified as an influence, but also genetic variants operating in brain regions associated with motor function. The researchers also investigated whether the genetic markers identified were linked to children's physical and cognitive development.

They identified that a relatively later age a child begins walking was influenced by some genes involved in higher educational attainment. This research also suggested that there may be a genetic correlation between walking earlier and the presence of attention deficit hyperactivity disorder (ADHD). However, the paper reported that this correlation 'while significant, is still relatively modest in magnitude'.

Corresponding author Professor Angelica Ronald from the University of Surrey said: 'We hope these new genetic findings can advance fundamental understanding about the causes of walking and be used to better support children with motor disorders and learning disabilities.'

The researchers suggested future work could investigate whether genetic markers could be applied to improve prediction models for clinically relevant conditions, and whether early walking could act as an early indicator of ADHD.

It is worth noting that a limitation of this research, which the authors acknowledged in the paper, was that the GWAS was conducted specifically on Western European genetic data.