MINNEAPOLIS – Sleep is in short supply, thanks to our “24-hour society” in which trading sleep for work or play is commonplace and sleep deprivation is worn as a badge of honor, according to Dr. Michel Cramer Bornemann, codirector of the Minnesota Regional Sleep Disorders Center at Hennepin County Medical Center in Minneapolis.
Not only have we become accustomed to trading sleep for work, Dr. Cramer Bornemann said at the meeting “lack of sleep is synonymous with hard work or achievement, when really it can impede both.” In fact, the effects of insufficient shut-eye extend across multiple domains, according to a collection of independent studies presented at this year's meeting. For example, sleep loss was linked to the development or exacerbation of symptoms of ADHD in early childhood, an individual's genetic risk of obesity, inhibitory response to images of high-calorie foods, and even marital discontent.
ADHD and Sleep Loss
In a study designed to tease out the complex relationship between sleep problems – particularly falling asleep and staying asleep – and the development or worsening of inattention and hyperactivity and impulsivity in children and adolescents diagnosed with ADHD, Erika Gaylor, Ph.D., of SRI International in Menlo Park, Calif., and her colleagues analyzed data from the preschool and kindergarten waves of the Early Childhood Longitudinal Study–Birth Cohort. The cohort comprises a representative sample of approximately 6,860 children and their families living the United States.
The investigators calculated total nighttime sleep duration based on parent-reported bedtime and wake time. “We performed two sets of regression analyses to identify whether sleep duration in preschool-age children predicts attention and hyperactivity at kindergarten entry and [whether] attention and hyperactivity symptoms at preschool predict sleep duration at kindergarten,” she explained.
Controlling for the outcome of interest at the preschool time point, sex, ethnicity, and family income, researchers found that less sleep at preschool significantly predicted worse scores on parent-reported hyperactivity and attention at kindergarten, whereas parent-reported hyperactivity and attention at preschool did not predict sleep duration at kindergarten, Dr. Gaylor stated.
The results extend those of a previous study in which she and her colleagues determined that having a consistent bedtime was the most reliable predictor of positive developmental outcomes by age 4 years, she noted.
The Obesity Link
In a twin study designed to look more closely at the previously reported link between short sleep duration and elevated body mass index, Dr. Nathaniel Watson of the University of Washington in Seattle and his colleagues determined that short sleep may potentiate an underlying genetic mechanism for obesity.
The investigators examined whether sleep duration modified genetic and environmental influences on BMI in 1,811 pairs of twins drawn from the population-based University of Washington Twin Registry. The mean age of the study participants was 36.6 years. The participants provided self-reported information on height and weight, which was used to calculate BMI, as well as on habitual sleep duration, Dr. Watson said. The mean BMI of the group was 25.4 kg/m
Using behavioral genetic interaction models, the investigators found significant relationships between habitual sleep duration and genetic and shared environmental influences on BMI. Specifically, longer sleep duration was associated with decreased BMI, Dr. Watson reported. “When sleep duration was 7 hours, the heritability of BMI was more than double [70%] that observed when sleep duration was 9 hours [33%],” he said, noting that “there appears to be something about short sleep that creates a permissive environment for expression of obesity-related genes.”
The findings are an important addition to the existing body of research on the relationship between sleep duration and BMI, Dr. Watson said.
A connection between sleepiness and lack of self-control with respect to dietary choices may also contribute to the sleep loss/obesity equation, according to a study presented by William Killgore, Ph.D., of Harvard Medical School in Boston.
To test their hypothesis that greater daytime sleepiness correlates with reduced prefrontal cortex response during passive viewing of images of high-calorie foods, Dr. Killgore and his colleagues analyzed the functional MRI scans of 12 healthy adults obtained while they were shown pictures of high-calorie foods, low-calorie foods, and control images of plants and rocks. The researchers correlated the fMRI findings with subjects' self-reported daytime sleepiness, assessed via the Epworth Sleepiness Scale (ESS).
“Greater ESS scores correlated with reduced activation in the dorsolateral prefrontal cortex when high-calorie vs. low-calorie food images were perceived,” Dr. Killgore said, noting that this region is typically implicated in attention and inhibitory processing. Greater daytime sleepiness was also associated with increased activation in the right parietal and inferior temporal cortex, he said.