Children slept mean (SD) durations of 12.3 (1.9) h/d at age 6 months, 12.8 (1.6) h/d at age 1 year, and 12.0 (1.2) h/d at age 2 years. The weighted mean (SD) daily sleep duration from ages 6 months to 2 years was 12.3 (1.1) hours. At age 3 years, the mean (SD) for BMI z score was 0.44 (1.03), for SS + TR was 16.66 (4.06) mm, and for SS/TR was 0.64 (0.16); 9% of the children were over-weight.
In bivariate analyses (), we observed an approximately 2-fold higher prevalence of overweight among children who slept less than 12 hours in a 24-hour period. Although fewer hours of sleep were associated with higher overweight prevalence across the range (), we observed the steepest increase in overweight among children who slept less than 12 hours in a 24-hour period. We thus dichotomized infant sleep duration to less than 12 h/d vs 12 h/d or more in further analyses. Children whose parents were single or divorced or who lived in homes with lower household incomes and lower maternal educational attainment were more likely to sleep less than 12 h/d (). In addition, children who were black, Hispanic, or of other race/ethnicity were more likely than white children to sleep less than 12 h/d (). Shorter sleep duration was also associated with more hours of television viewing ().
Unadjusted relationship of infant sleep duration with overweight prevalence at age 3 years. Data from 915 Project Viva participants.
Bivariate Associations of Selected Parent and Child Characteristics With Infant Sleep Duration, With Data From 915 Mother-Infant Pairs From Project Viva
In multivariate analyses, adjusting for maternal education, income, prepregnancy BMI, marital status, prenatal smoking history, and breastfeeding duration and child's race/ethnicity, birth weight, 6-month weight-for-length z score, average daily television viewing, and daily participation in active play, we found that infant sleep of less than 12 h/d was associated with a higher BMI z score (β, 0.16; 95% CI, 0.02−0.29), higher SS + TR (β, 0.79; 95% CI, 0.18−1.40), and increased odds of over-weight (odds ratio, 2.04; 95% CI, 1.07−3.91). Adjustment for child's television viewing and participation in active play only minimally changed the observed associations between sleep duration and our anthropometric outcomes ().
Associations of Infant Sleep Duration With Child Anthropometry at Age 3 Yearsa
Compared with children with high levels of sleep and low levels of television viewing, those with low levels of sleep or high levels of television viewing separately had somewhat increased odds of overweight and adiposity (). However, the combination of low levels of sleep and high levels of television viewing appeared to be synergistic and was associated with markedly higher BMI z scores, SS + TR, and SS/TR and increased odds of overweight (). In , we show the covariate-adjusted predicted probability of overweight at age 3 years among the 4 combinations of sleep and television viewing. Children who slept less than 12 h/d and viewed 2 h/d or more of television had a predicted 3-year over-weight probability of 17%.
Associations Between Infant Sleep Duration and Television Viewing With Child Anthropometry at Age 3 Yearsa
Figure 2 Predicted percentage of overweight at age 3 years according to daily sleep duration and television viewing, adjusted for child race/ethnicity, birth weight, and breastfeeding duration and maternal smoking status, education, household income, marital status, (more ...)
In secondary analyses, we examined contemporaneous changes in sleep duration with changes in weight-for-length z score during a 3-year period. Between ages 6 months and 1 year, children increased their mean (SD) sleep duration by 0.50 (1.97) h/d and decreased their mean (SD) weight-for-length z scores by 0.43 (0.81). From ages 1 to 2 years, children decreased their mean (SD) sleep duration by 0.79 (1.48) h/d and decreased their mean (SD) weight-for-length z score by 0.29 (0.94). Finally, from ages 2 to 3 years, children decreased their mean (SD) sleep duration by 0.80 (1.26) h/d and increased their mean (SD) weight-for-length z score by 0.40 (0.85). After adjusting for maternal education, income, prepregnancy BMI, marital status, prenatal smoking history, and breastfeeding duration and child's race/ethnicity, change in television viewing, birth weight, and baseline adiposity, the mean weight-for-length z score increased by 0.02 (95% CI, 0.003−0.05) for each 1-h/d decrease in sleep duration ().
Multivariate-Adjusted Interval Change in Weight-for-Length z Score Associated With Change in Sleep Duration From Ages 6 Months to 3 Yearsa