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Sleep debt takes toll in multiple domains: lack of shut-eye linked to ADHD in children, and risk of obesity and marital friction in adults.


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 shuteye 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, and assessed children's behavior using brief measures of attention and task persistence, Dr. Gaylor reported. "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 said.

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. "These findings suggest that some children who are not getting adequate sleep may be at risk for developing behavioral problems manifested by hyperactivity, impulsivity, and problems sitting still and paying attention," she said. 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.sup.2], and the mean sleep duration was 7.18 hours.

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."

Similarly, he added, longer sleep duration may suppress genetic influences on body weight.

The findings are an important addition to the existing body of research on the relationship between sleep duration and BMI, Dr. Watson said.

"Studies attempting to identify specific genotypes for BMI may benefit from considering the moderating role of sleep duration."

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 magnetic resonance imaging (fMRI) 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.

Using a second-level regression model, 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 reported, noting that this region is typically implicated in attention and inhibitory processing.

Similarly, greater daytime sleepiness was also associated with increased activation in the right parietal and inferior temporal cortex, he said.

The findings suggest the possibility that sleepiness may affect an individual's inhibitory control when he or she is exposed to highly appetizing, high-calorie foods, according to Dr. Killgore, although it's uncertain as of yet whether the observed patterns relate to actual food consumption, he said.

Marital Discord

Although most sleep research focuses on the individual, the fact that sleep problems and relationship trouble often co-occur led Wendy M. Troxel, Ph.D., of the University of Pittsburgh, and her colleagues to consider the dyadic nature of sleep in a recent study.

The investigators examined the bidirectional links between nightly sleep and daily marital interactions among 35 healthy married couples (mean age, 32 years) by correlating the actigraph results for sleep latency, wakefulness after sleep onset, and total sleep time of each partner over 10 nights, with daily self-reported positive and negative marital interactions assessed via electronic diaries during the same period.

"We found stronger evidence linking sleep to the next day's marital interactions, rather than the reverse direction," Dr. Troxel reported.

Specifically, wives' prolonged sleep latency significantly predicted their own and their husbands' reports of more negative and less positive interactions the next day, even after adjustment for depressive symptoms, whereas the quality of marital interactions did not appear to predict sleep measures in women, she said.

The sleep quality of husbands did not appear to affect their own or their wives' reports of next-day marital interactions; however, for men, a higher level of positive marital interactions predicted shorter total sleep duration the next night.

The findings suggest, perhaps, that "men are more likely to repress their feelings or not be as aware" of mood changes, whereas women are more likely to express their emotional concerns and to "drive the emotional climate of the relationship," Dr. Troxel said. The results highlight the potential interpersonal consequences of sleep disorders, and as such may have important clinical implications, she said.

In March of this year, the Centers for Disease Control and Prevention reported that nearly a third of the country's adults get fewer than the minimum recommended 7 hours of sleep per night, and it's not because they're not tired: Nearly 40% of the survey population reported unintentionally falling asleep during the day, and nearly 5% reported nodding off while driving in the preceding 30 days (MMWR 2011;60:233-8).

In addition to the negative consequences of sleep deprivation noted above, previous studies have linked sleep insufficiency to a range of adverse health outcomes, including cardiovascular disease, asthma, diabetes, and stroke, according to the report.

The presenters reported no financial conflicts of interest relevant to their respective presentations.
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Author:Mahoney, Diana
Publication:Family Practice News
Date:Aug 1, 2011
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