Sleeping longer hours correlates with IQ: study

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By Yoon Ja-young

If you are one of those parents making your children sit up late doing homework, you'd better think again. A study revealed that children sleeping longer hours tend to have higher IQs.

According to a joint research by the Environmental Health Center at Seoul National University's College of Medicine and Kim In-hyang, a professor at Hanyang University Medical Center, six-year-old children who sleep longer scored higher in verbal IQ evaluation tests, compared with their peers who sleep less.

The research is based on 538 six-year-olds who have been included in the center's cohort. Designated by the Ministry of Environment in 2008, the center has been conducting research on children in Seoul, Incheon and Gyeonggi Province to verify the correlations between the exposure to various environmental factors and the development of their physical, neurological and cognitive abilities.

It showed that, the longer hours children sleep, the higher their IQ scores.

This was especially the case with boys. Boys who sleep more than 10 hours a night score 10 points higher than those who sleep less than 8 hours a night. However, the correlation was not found among girls.

"The National Sleep Foundation recommends that children before school age sleep between 10 and 13 hours, and that school-aged children sleep for 9 to 11 hours, per night. In Korea, however, 86.1 percent of children aged 7 to 8 sleep less than nine hours each night. "Children are indeed lacking in sleep," the research team noted.

Hong Yun-chul, a professor at Seoul National University Medical School who heads the center, noted that the research showed that children's sleeping hours not only affect their physical development, but also play an important role in the development of their cognitive abilities as well as their immune systems. He added that there have been similar studies conducted overseas that also showed the correlation between the length or quality of sleep and the development of cognitive abilities in children. He said that further research is needed, due to the difference in results between boys and girls.

The study was published in the "International Journal of Behavioral Medicine."

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