Previous research suggests that short sleep duration and later bedtimes are associated with higher body mass index (BMI) and lower physical activity levels in children. We sought to determine if objective measurements of sleep duration and timing were correlated with BMI percentile and/or physical activity measures in low-income, minority children. Data were collected from 104 8- to 10-year-old children (58% female; 88.5% Latino or African-American; 51.9% overweight or obese) who were instructed to wear an accelerometer at their waists for 1 week. Data were manually analyzed to determine average sleep-onset (i.e. bedtime), sleep-offset (i.e. wake time), sleep duration, and minutes of wake after sleep-onset (WASO) for each subject. Physical activity measures, calculated from previous analyses of these data, included minutes of moderate and vigorous physical activity (MVPA), sustained bouts of MVPA, minutes of vigorous physical activity (VPA), and bouts of VPA. We used Student t-tests and linear regressions to analyze relationships between BMI percentile, sleep variables, and physical activity variables. Only 7% of children averaged the recommended 10-11 hours of nightly sleep. We found a weak but statistically significant association between shorter sleep duration and increased BMI percentile. None of the other sleep variables, or any physical activity measure, was associated with increased BMI percentile. We conclude that minority children living in low-income communities, particularly those with a higher BMI, get less than the recommended nightly sleep. Future research needs to focus on causes and consequences of these sleep patterns to determine if increased sleep recommendations should be a routine part of obesity prevention and treatment strategies.
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