Insufficient sleep duration in children may be associated with poor diet, obesity and more screen time, a study warns.
The study, published in the Journal of Clinical Sleep Medicine, shows that less sleep was linked with unhealthy dietary habits such as skipping breakfast, fast-food consumption and consuming sweets regularly.
Insufficient sleep duration also was associated with increased screen time and being overweight/obese, researchers said.
"Approximately 40 per cent of schoolchildren in the study slept less than recommended," said Labros Sidossis from Rutgers University in the US.
"Insufficient sleeping levels were associated with poor dietary habits, increased screen time and obesity in both genders," Sidossis said.
The American Academy of Sleep Medicine recommends that children six to 12 years of age should sleep nine to 12 hours on a regular basis to promote optimal health.
Teenagers 13 to 18 years of age should sleep eight to 10 hours.
Population data were derived from a school-based health survey completed in Greece by 177,091 children (51 per cent male) between the ages of 8 and 17 years.
Dietary habits, usual weekday and weekend sleeping hours, physical activity status, and sedentary activities were assessed through electronic questionnaires completed at school.
Children who reported that they usually sleep fewer than nine hours per day, and adolescents sleeping fewer than eight hours per day, were classified as having insufficient sleep.
A greater proportion of males than females (42.3 per cent versus 37.3 per cent) and of children compared with adolescents (42.1 per cent versus 32.8 per cent) reported insufficient sleep duration.
Adolescents with an insufficient sleep duration also had lower aerobic fitness and physical activity.
"The most surprising finding was that aerobic fitness was associated with sleep habits," said Sidossis.
"In other words, better sleep habits were associated with better levels of aerobic fitness. We can speculate that adequate sleep results in higher energy levels during the day," he said.
"Therefore, children who sleep well are maybe more physically active during the day and hence have higher aerobic capacity," said Sidossis.
The researchers noted that the results support the development of interventions to help students improve sleep duration.
"Insufficient sleep duration among children constitutes an understated health problem in Westernised societies," he said.