“Too little sleep 'can make children hyperactive'” according to The Daily Telegraph. The newspaper says that a new study suggests that a lack of sleep makes it more likely that children will “develop behavioural problems and become hyperactive”.
This study of 280 seven and eight-year-olds from Finland looked at whether how long they slept affected their levels of symptoms of attention deficit hyperactivity disorder (ADHD). It found that children who slept for less than 7.7 hours on average scored higher on tests of hyperactivity and impulsivity than those who slept for longer.
It is important to remember that this study looked only at levels symptoms associated with ADHD, and that it was unclear whether any of the children would actually have been medically considered to have ADHD. Another major limitation was that it measured sleep duration and ADHD symptoms during the same time period and therefore could not determine whether shorter sleep times might cause ADHD symptoms or vice versa. This and other limitations mean a causal link between sleep duration and ADHD symptoms has not been proven by this study.
Dr E Juulia Paavonen and colleagues from the University of Helsinki and other research centres in Finland carried out this research. The study was funded by various organisations including the Academy of Finland, the European Science Foundation and the Finnish Foundation for Pediatric Research. The study was published in the peer-reviewed medical journal Pediatrics.
This was a cross-sectional study on the relationship between sleep duration and levels of behavioural symptoms of attention-deficit/hyperactivity disorder (ADHD) in children.
The participants in the study were recruited from a cohort of 1,049 children born from March to November of 1998 in Helsinki, Finland. In 2006, the researchers invited 413 of these children and their parents to participate in the current study, and 321 agreed.
The researchers excluded children with neurological conditions that might affect sleep or behaviour.
To assess their sleep the children were asked to wear a monitor called an actigraph on their wrist for seven days. Parents were also asked to record when the children went to bed, got up, took off the monitor, and if the children experienced any problems or conditions that might affect sleep during the monitoring period.
The researchers excluded data from any nights when the actigraph was not used, when information about bedtime or other factors was not available, when the parental report of bedtime and the actigraph recordings did not agree, or when the parent reported that the child’s sleep pattern was significantly different from usual (e.g. due to travel or illness).
The children’s parents were given standard questionnaires about the children’s sleep patterns and their levels of symptoms associated with ADHD. This symptom questionnaire measured levels of hyperactivity/impulsivity and inattention, and these scores were added to give a score indicating the overall level of ADHD symptoms, known as the ‘ADHD total symptom score’.
In their final analysis, researchers included 280 children (146 girls and 134 boys with an average age of 8.1 years), who provided complete data. The researchers defined the children as:
The researchers used statistical methods to compare behavioural symptoms between these groups of children. Some of their analysis took into account other factors that might affect duration of sleep (potential confounding factors), such as age, sex, parental level of education, height, body mass index, mother’s age, and neurologic and other illnesses such as dyslexia, dysphasia and eczema.
Using data on sleep length collected by the actigraph, the researchers found that children who slept for the least amount of time (less than 7.7 hours a night) scored higher on both the hyperactivity/impulsivity and ADHD total symptom scales when compared with children who slept for longer. There was no difference in inattention score between children who slept less than 7.7 hours a night and those who slept more.
After taking into account all of the potential confounding factors, only the link between shorter sleep and higher hyperactivity/impulsivity symptoms remained significant. When the researchers looked at parent-reported sleep duration rather than actigraph readings, they found no significant association with ADHD symptom scores.
The researchers concluded that “short sleep duration and sleeping difficulties increase the risk
for behavioral symptoms of attention-deficit/hyperactivity disorder” in children. They also recommend that intervention studies be performed to confirm the causality.
The main limitations of this study relate to the difficulties measuring sleep or symptoms of ADHD and in proving that one factor is actually causing the other:
Getting a sufficient amount of sleep is important in both children and adults. It will require further studies looking at children’s sleep patterns over time and any subsequent development of diagnosed ADHD in order to determine whether there is a causal link with this disorder.