A University of South Australia study shows that school children between the ages of 10 and 15 years are averaging at least 30 minutes less sleep than children of the same ages did more than 20 years ago.
Many children who go to bed late are inattentive and unable to function effectively at school because they are sleep deprived, according to Dr Jim Dollman from the School of Health Sciences, who led the study.
The study compared data collected on children who participated in the 1985 Australian Schools Health and Fitness Survey and the 2004 SA Physical Activity Survey. Both surveys involved children from the same cluster of eight SA schools.
?Almost all of the reduced sleep time is attributable to later bed-time and an average of seven minutes earlier wake-time,? Dr Dollman said.
While the 1985 survey showed no differences between boys and girls for bed-time, wake-up time and total sleep time, reduced average sleep times were found in both girls (28 minutes) and boys (33 minutes) in the 2004 survey. Sleep reduction was more pronounced in boys of lower socioeconomic status (SES) (44 minutes), than in higher SES boys (23 minutes).
?This suggests that current guidelines concerning age and sleep length are more often breached than not. Contributing to this is a general lack of awareness in the community concerning the amount of sleep needed by children and how this varies across age,? Dr Dollman said.
?A recent poll on sleep conducted in America shows that more than half of USA adolescents know that they sleep less than they should to ?feel their best?, and yet 90 per cent of parents believe that their children are getting sufficient sleep for at least a few nights during the school week,? he said.
Associate Professor Kurt Lushington from UniSA?s Centre for Sleep Research recommends the following sleep guidelines – three to five years (11 – 13 hours), five to 12 years (10 ? 11 hours), and 12 to 18 years (8 ? 10 hours).
?The UniSA study was confined to school days from Sunday to Thursday evenings and did not include school holidays or weekends. Recording such data might have allowed us to determine whether catching up on sleep during holidays and weekends offsets any loss of sleep during the school week,? Dr Dollman said.
The reduced sleep times seen in the 2004 survey correspond with the difference in sleep duration between normal weight and over-weight children recorded in a separate study undertaken by W Agras (Stanford University School of Medicine), which followed 150 children from birth to 9.5 years of age. This suggests that changing sleep patterns are contributing to the prevalence of weight increase among Australian children.
?Social trends such as increased part-time work by adolescents, increases in the number of computers, televisions and play stations in bedrooms, and children using mobile phones, would indicate that ?lights out? is less likely to coincide with the onset of sleep among youth today, leading to an overestimation of sleep time in the 2004 survey, and resulting in an underestimation of sleep losses between 1985 and 2004,? Dr Dollman said.
?The results of this study underline the importance of routinely monitoring sleep behaviours of children and adolescents.?