Low sleep and low socioeconomic status predict high body mass index: a 4-year longitudinal study of Australian schoolchildren


Address for correspondence: Professor JA O'Dea, Health Education & Nutrition Education, Faculty of Education & Social Work, University of Sydney, Building A35, Sydney, NSW 2006, Australia. E-mail: jennifer.odea@sydney.edu.au



The objective of this study was to examine the longitudinal relationships between body mass index (BMI), sleep duration and socioeconomic status (SES) in a 4-year cohort of 939 children aged 7–12 years.


Children and their mothers completed an annual questionnaire to assess usual weekday sleep and wake times, amount of sleep, physical activity, parental education and school SES. 93% of children were enrolled (939/1010) and retention was 88%, 83% and 81% in consecutive years. Height and weight were measured annually.


BMI increased with decreasing amount of sleep and less sleep predicted greater International Obesity Task Force measures of obesity and overweight. In all 4 years, after controlling for baseline BMI, low SES was a significant predictor of high BMI. Children in the upper tertile of sleep in year 1 had a 2.3 kg lower weight gain (standard error [SE]: 0.5) between years 1 and 4 (P < 0.0001) than children in the lower tertile of sleep and a 0.45 kg m−2 lower increase in BMI (SE: 0.15) (P = 0.004). The difference between children with consistently low and high sleep duration over 4 years was 1 BMI point. Those with the lowest BMI were the children with both high SES and high sleep duration. PA was not associated with BMI.


Both low SES and short sleep duration predict obesity risk in children after controlling for baseline BMI and this trend becomes stronger as children enter adolescence. Obesity prevention should include a sleep promotion component and this may be more beneficial to children of low SES and/or socially disadvantaged backgrounds.