Last August,a study in the journal Sleep Medicine said children who go to bed after nine o'clock took longer to fall asleep and slept less.

VOA: special.2010.06.09

It said they were getting far less sleep than they should.

VOA: special.2009.06.02

The mice with the mutation needed less sleep than normal mice.

VOA: special.2009.08.26

People who have this mutation need less sleep than others.

VOA: special.2009.08.26