Scientists have confirmed parent's long-held suspicions that activity during the day sends kids to sleep faster.

Daily activity sends kids to sleep faster, say researchers (Source: iStockphoto)

The research, published in Archives of Disease in Childhood, also found that sedentary behaviour delays the onset of sleep.

Paediatric sleep specialist and study author Dr Gillian Nixon, of the Monash Institute of Medical Research, says this research demonstrates the importance of physical activity not only for weight control and fitness, but to promote good sleep.

Nixon says parents have probably always known "running children ragged" puts them to sleep quicker, but now it has been demonstrated scientifically.

The study measured the daily activity of close to 600 children from New Zealand, all aged 7 years.

The children wore accelerometers, much like pedometers, around their waist, which quantified how active they were each minute of the day.

"The devices tell us whether the children are sedentary, walking around or doing vigorous activity, which is something equivalent to running," says Nixon.

The same device was then used to measure how long the children took to fall asleep.

"As you fall asleep your movement falls below a certain threshold and the device can measure when you reach that threshold," she says.

The study found that on average children took 26 minutes to fall asleep.

Nixon says children fell asleep almost 6 minutes faster for every hour of vigorous activity they did.

But it was only vigorous activity that shortened the onset of sleep in children, she says.

"Moderate activity didn't come out in the analysis as being important."

Sitting bad for sleep

Nixon and colleagues also found that for every hour a child spent being sedentary, it took them 3 minutes longer to fall asleep at night.

Children also took longer to fall asleep in lighter, summer evenings, says Nixon.

"It's much harder to go to sleep physically when it's light because light helps to regulate our body clock."

Nixon says an important finding of the research is that the quicker children were able to fall asleep the more sleep they got.

"That seems obvious but falling asleep quickly is a marker of children who can stay asleep and get a good long sleep through the night."

Implications

Not getting enough sleep has health implications as well as affecting concentration and learning, says Nixon.

In recent years, Nixon says an association has been found between lack of sleep and obesity.

"In both adults and children short sleep time is linked with obesity," she says.

Nixon hopes to restudy the same cohort of children in the future to see if their sleep patterns change as teenagers or adults.