A decrease in sleep efficiency is linked to lower cognitive functioning in boys and in African American children

In the study of cognitive development in children, it is well known that sleep problems – including too little or broken sleep – are linked to lower cognitive performance. A new study by Dr Lauren Philbrook, Dr Mona El-Sheikh and colleagues at Auburn University in Alabama, USA, looked in more detail at the patterns in a group of children experiencing social and economic difficulty.

They found three things:

• There is no statistical correlation between cognitive performance and how long children sleep, but there is a link between broken sleep and poorer cognitive performance.
• This correlation is not seen in all children, only in African American children and in boys.
• These children didn’t fall further behind their peers over the two years of the study – their performance was lower by the same amount over the whole period.

The study involved 282 nine-year-olds. The researchers measured their sleep over seven nights using a device attached to their wrist. They also measured the children’s cognitive functioning at that time, again one year later, and again a year after that when the children were 11. Their general intellectual ability was tested (verbal comprehension, visual matching, concept formation), as were their working memory (repeating series of numbers and words read to them) and their processing speed (for example, speed of recognising objects).

The study of cognitive development in children shows that better sleeping helps the brain develop and mature. Children who sleep better are also more alert during the day and so able to learn more.

Why did poor sleep lower cognitive functioning only in African American children? Perhaps they have additional pressures in their lives, for example, the experience of discrimination.

And why were boys more affected than girls? We know that boys have higher levels of behavioural problems – that is, they have more difficulty controlling themselves. Perhaps when behavioural problems are coupled with poorer sleeping, boys become particularly vulnerable to lower cognitive performance.

The study’s findings suggest that family support programmes, such as parenting programmes, should include ways to help children with sleep.

The study was supported by a grant from the National Heart, Lung, and Blood Institute awarded to Mona El-Sheikh.