"Sometimes kids will say that 'I feel like I have to kick my legs' or 'I feel like I have to move my legs to get comfortable.'"

That's restless legs syndrome, a genetic disorder that Mayo Clinic pediatric neurologist and sleep specialist Dr. Suresh Kotagal says is more common in children than you might think.

Studies show that 1 in 50 kids have the condition, a discomfort that can prevent a child from falling asleep and repeatedly wake a child during sleep.

"They are tired in the daytime and frequently have troubles with attention span."

It often can be related to low levels of iron, which helps make dopamine, a chemical that helps in neurotransmission in the brain and learning.

"So if we don't have enough dopamine, one is likely to have disturbed sleep."

Dr. Kotagal says children with restless legs syndrome may go undiagnosed because there is a lack of awareness of the condition, and it can be attributed to attention deficit hyperactivity disorder instead.