Lack of Sleep in Children Linked to ADHD Symptoms

Caroline Cassels

April 28, 2009

April 28, 2009 — Inadequate sleep in children appears to be an independent risk factor for behavioral symptoms of attention-deficit/hyperactivity disorder (ADHD), new research suggests.

In a cross-sectional study of 7- to 8-year-old children, investigators at the University of Helsinki, Finland, found that short sleepers — those who got less than 7.7 hours of sleep per night — were significantly more likely to be hyperactive/inattentive compared with children who were moderate or longer sleepers.

"There is a large amount of literature linking sleeping difficulties to behavioral symptoms. However, this study shows short sleep duration itself is related to behavioral symptoms, independent of sleeping difficulties," principal investigator E. Juulia Paavonen, MD, PhD, told Medscape Psychiatry.

The study is published online April 27 in Pediatrics.

National Problem

It is estimated that up to one-third of children in the United States suffer from inadequate sleep, suggesting it may be a "nationally significant problem," said Dr. Paavonen. This is true not only in the United States, she added, but also in Finland, where research has shown that Finnish children sleep less than children elsewhere in Europe, suggesting inadequate sleep may be a particular problem in this country.

Previous studies have shown that ADHD is often associated with sleep difficulties, and children with sleep apnea often display behavioral symptoms. In addition, said Dr. Paavonen, experimental studies in children suggest that sleep restriction significantly affects attention and cognitive performance. However, she pointed out that none of the previous research has included behavioral assessments.

To determine whether sleep duration (vs sleep difficulties) plays a role in children's behavioral symptoms, the investigators performed a cross-sectional study in 280 children (146 girls, 134 boys) with a mean age of 8.1 years.

Parents filled in the 26-item Sleep Disturbance Scale for Children. Sleep quality was objectively measured using actigraphs. Children were required to wear the devices on their nondominant wrist continuously for 7 days. Parents kept a log of bed times, rise times, monitor removal times, and daily problems or conditions that might alter sleep quality, such as illness.

Behavioral symptoms of ADHD were evaluated by using the maternal ratings of the ADHD Rating Scale, which consists of hyperactivity/impulsivity and inattention subscales. Demographic data, including socioeconomic status and parental education level, were also collected.

Short sleepers were defined as those who slept 7.7 hours on average. Average sleepers were those who slept 7.7 to 9.4 hours a night, and long sleepers were defined as those who slept more than 9.4 hours a night.

Of the total group, 26 (9.3%) were short sleepers, 226 (80.7%) average sleepers, and 28 (10%) were long sleepers.

Parent-reported sleep durations were much higher than objectively measured sleep duration and were not related to behavioral problems. The large discrepancy between objectively registered sleep duration and parent-reported sleep duration was somewhat surprising, said Dr. Paavonen.

She added that this finding suggests that some parents may not know how much their children truly sleep or that some parental reports may be affected by what she described as "social desirability bias," where some parents may overreport their children's actual sleep duration, she added.

Clear Result

Not unexpectedly, the investigators found that children with sleeping difficulties had higher scores on all ADHD subscales than other children, including hyperactivity/impulsivity and inattention.

The results also showed that both objectively measured short sleep duration and parent-reported sleeping difficulties were independently associated with an increased risk for behavioral symptoms of ADHD, which was not explained by confounding factors.

"Even though we hypothesized that sleep duration would affect behavioral symptoms, we were somewhat surprised that the effect was so very, very, clear," said Dr. Paavonen.

These findings, she added, suggest short sleep duration may be an independent risk factor for behavioral symptoms in children and that maintaining adequate sleep schedules among children is likely to be important in preventing behavioral symptoms.

"There is a large individual variation in sleep requirements, so we are not saying that all short sleepers suffer from sleep deprivation. But I would suggest that in children with behavioral problems, parents and clinicians should consider a trial of sleep lengthening to see if it improves behavior," she said.

A previous European study showed that lengthening sleep in children by as little as 30 minutes significantly improved cognitive test scores and that this improvement was observed less than a week after starting the intervention.

Dr. Paavonen cautioned that because this is 1 of the first studies to show that sleep duration may influence behavioral symptoms, the results need to be replicated. Further, she added, intervention studies testing the impact of lengthened sleep on behavioral outcomes are needed to prove causality.

The authors report no conflicts of interest.

Pediatrics. Published online April 27, 2009.

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