Children aged four and under who get less than 10 hours of sleep a night are nearly twice as likely to be overweight or obese five years later, according to a US study.
Researchers in the US looked at the relationship between sleep and weight in 1,930 children aged zero to 13 years old in 1997, and again in 2002.
For children who were four years old or younger at the time of the first survey, sleeping for less than 10 hours a night was associated with nearly double the risk of being overweight or obese at the second survey.
Dr Janice F Bell from the University of Washington said this study suggested that early childhood could be a "critical window" when night-time sleep helps determine a child's future weight status.
According to the USA's National Sleep Foundation, toddlers one to three years old should sleep for 12 to 14 hours a night; children aged three to five should sleep 11 to 13 hours, while five- to 10-year-olds should get 10 to 11 hours. Teens should get 8.5 to 9.25 hours of sleep nightly.