Children with autism have poorer sleep quality than children without the condition and this problem continues right up to their teens, a new study has shown.

Autism, also known as autism spectrum disorder (ASD), is a biological disorder of the brain that impairs communication and social skills. Signs can include an absence of eye contact, apparent aloofness, avoidance of physical contact even with family, difficulty dealing with interruptions to routine and a lack of interest in other children and what they are doing.

While disrupted sleep has been linked to autism before, studies have been small and inconsistent. UK scientists decided to look into this further.

They analysed data from a long-term study involving over 14,000 children born in the early 1990s. All of the parents were asked about their children's sleeping patterns when they were six, 18 and 30 months old, and again when they were three-and-a-half years old, five, six, nine and 11.

Almost 90 of the children were diagnosed with autism by the age of 11 and for the purpose of this study, the scientists focused on 39 of the children with autism and over 7,000 children without the condition.

The study found that before the age of 30 months, there was very little difference in the sleeping patterns of children whether they had autism or not. However, from 30 months onwards, things seemed to change.

Those with autism tended to get less sleep overall, with the biggest discrepancy - 43 minutes per night - persisting up to the age of 11.

After that, the gap in total sleep obtained lessened, but those with autism were still getting around 20 minutes less sleep per night than their peers by the time they reached their teens.

These differences in the amount of sleep obtained were due to frequent bouts of waking in the night by the young people with autism.

In fact, after the age of 30 months, children with autism were much more likely than their peers to wake three or more times a night. By the age of six, 10% of children with autism were still waking three or more times per night compared to 0.5% of their peers.

While it is not known what impact this may have, the scientists noted that other researchers have suggested that it may impact on neuronal (nerve cell) development.

"If this hypothesis of cumulative sleep reduction resulting in neuronal loss is confirmed, then clinically children with autism might gain from even a small consistent increase in total sleep time," they said.

Details of these findings are published in the journal, Archives of Disease in Childhood.