Napping beyond the age of 2 is linked to poorer sleep quality in young children, according to a recent study.

Researchers found that napping beyond the age of 2 years old lengthens the amount of time it takes for a child to fall asleep (sleep onset) and shortens the overall amount of night-time sleep s/he has.

The total length and quality of sleep over a 24 hour period is linked to child health and development, and parents and careers have been encouraged to let toddlers take a daytime nap as a way of promoting good health. By the time a child is 2, s/he is generally getting most of his/her sleep at night.

"The impact of night sleep on children's development and health is increasingly documented, but to date there is not sufficient evidence to indicate the value of prolonging napping, whether at home or in childcare contexts, once sleep has consolidated into night," write the researchers.

For the study, researchers reviewed the available published evidence for napping in children up to the age of 5 years, and found 26 relevant studies out of a total of 781. They pooled the data and synthesized the findings.

The links between napping and any detrimental impact on behavior, development, and overall health, however, were less clear-cut, largely because of the differences in age and napping patterns of the children studied.

The researchers suggest that the quality of studies reflects the relatively new focus of research on the effects of napping, prompting them to call for further research to look at the complexities of sleep transition patterns in early childhood, and the impact of environmental factors in the home and/or childcare.

And they suggest that in pre-school children with sleep problems, it may be worth looking at whether they take regular daytime naps.

The findings are detailed in Archives of Disease in Childhood.