To understand the differences on sleeping-time between school-days and weekends among elementary school children.

This cross-sectional study was conducted from September to November, 2010. A stratified random cluster sampling strategy was used to select the participants, under diverse geographical and economic levels in eight provinces, municipalities or autonomous regions, in mainland China. A total number of 20 603 elementary school children aged from 6-12 years old were chosen as research subjects to record their time of sleeping during school-days or weekends.

Among the 6-12 year old, their time of sleeping was longer on weekends than that on school-days, while the average sleeping time during the weekends was longer in boys than in girls (t=3.35, P<0.05). However, there was no linearly decreasing trend along with the increase of age regarding the time of sleeping on weekends, in girls. Proportions of serious lack of sleep, lack of sleep or with sufficient sleep during the weekends were 13.63% (2 809/20 603) , 27.27% (5 618/20 603) and 59.10% (12 176/20 603). The proportion of sufficient sleep (over 50%) was significantly higher on weekends than that on school-days (less than 30%) , however, nearly one third of the first grade primary school children were sleep insufficiently even on weekends. Nearly 10.00% of the children under seriously or moderately lack of sleep on school-days were still in a serious lack of sleep state on weekends. The three groups who were categorized as serious lack of sleep (less than 9 h) , lack of sleep (9-10 h) or having sufficient (over 10 h) sleep on school-days accounted for 29.75%, 64.48%, 86.44%, respectively, when compared with the national regulation set as 10 h daily sleep for the children in China. The proportions of those whose time of sleep on weekends was less than school-days in the three groups as the same, moderate (within 1 h) , with 1 h caught-up or over, were 9.41%, 22.77%, 43.32%, 24.50%, respectively. The percentage of pupils who caught up sleep appropriately (within 1 h) on weekends among those who were serious lack of sleep in school-days would exceed 40.00% while the proportions among those who lack of sleep or having sufficient on school-days were 54.00% and 30.00%. The percentage of children who slept less on weekends than on school-days among those having sufficient sleep on school-days appeared the highest, nearly 20.00%. However, the proportions among those who lack of sleep or seriously lack of sleep on school-days were 3.45% and 8.16%, respectively.

We found that the elementary school children who could catch up time of sleep or lack of sleep on weekends coexisting in our study. This situation called for attention and the sleeping habit in primary school children should also be urgently improved.

Sleep; School-days; Weekend; Children