Children who sleep during the day have less sleep during the night and perform less well in puzzles designed to test their planning and organisational skills, according to preliminary studies.
Dr John Harsh and colleagues at the University of Southern Mississippi asked the parents of 738 children aged 2 years and above about their children’s sleeping habits. Children who took long daytime naps fell asleep at night an average of 39 minutes later.
The findings are backed by a study by Dr Kazuhiko Fukuda, of Fukushima University in Japan, reported in the magazine New Scientist. He compared children who attended all-day pre-schools – where 90-minute naps are compulsory – with children of the same age who napped only when they required.
As well as going to bed an average of 30 minutes later the children who took obligatory naps were more likely to be moody in the morning and resist going to school, according to their parents.
Napping may also affect mental performance, according to Dr Joe McNamara of the University of Florida. Dr McNamara measured how well 27 kindergarten children could solve puzzles that measure planning and organisational skills. The children who took longer naps completed fewer puzzles successfully – and the later they went to bed, the poorer their performance.
But although napping and non-napping children in Dr Harsh’s and Dr McNamara’s studies slept for the same amount of time in total Dr McNamara said, “napping is not a substitute for night-time sleep”.