1. Shorter sleep duration was associated with higher BMI, fat mass index, and insulin levels in children aged 9 to 10 years.
2. Sleep duration varied slightly by sex and ethnic group, but the relationship between sleep duration and type 2 diabetes (T2D) and cardiovascular risk factors were consistent across groups.
Study Rundown: Interest in understanding the risk factors associated with T2D and weight gain continues to increase in conjunction with the rising prevalence of these conditions. Previous studies have demonstrated an inverse relationship between sleep duration and obesity in children, but there is little known about the effects of sleep on determinants of T2D. This study examined the relationship between sleep duration, T2D and cardiovascular risk markers in a group of children aged 9 to 10 years old in the United Kingdom (UK). Results showed an inverse relationship between sleep duration and all measures of body size, adiposity, and T2D markers including insulin, insulin resistance, and fasting glucose. No association was found between sleep duration and HbA1c, lipid levels, or blood pressure. Sleep length differed only slightly between ethnic groups, but the relationships between sleep duration and the markers noted above were consistent across ethnic groups and sex. One limitation of this study was use of self-reported sleep times collected only on weekdays, which may represent an inaccurate total weekly sleep time. This study suggests increased sleep duration throughout childhood could have long-term impact on reducing T2D and adiposity later in life.
In-depth [cross-sectional]: This study included 4525 children, aged 9 to 10 years, from 200 primary schools in the UK. Schools with a high prevalence of South Asian and black African-Caribbean children were specifically selected to capture a multi-ethnic study population. Results showed average sleep time was 10.5 hours per night, with White Europeans having the longest average duration and black African-Caribbean children having the shortest (10.4 hours and 10.1 hours, respectively). Longer durations were more likely to be seen in girls (10.4 hours vs. 10.2 hours in boys) and younger children. An additional hour of sleep time was associated with 0.19 lower BMI (95%CI -0.28 to -0.09, p<.0001), 0.27kg lower fat mass (95%CI -0.42 to -0.11, p=.001), and a 2.88mU/L reduction in insulin levels (95%CI -4.50 to -1.23, p=.001). No difference was seen in HbA1c (-0.01, 95%CI -0.02 to 0.00, p=.11) or total cholesterol levels (-0.01, 95%CI -0.03 to 0.01, p=.32). These same relationships were seen across all ethnic groups and sexes, despite the baseline differences among ethnic groups and sexes.
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