"Rock-a-bye Baby" may seem like a harsh song to sing as you put a child to sleep ("When the bough breaks, the cradle will fall/and down will come baby, cradle and all"). But millions of little ones have dozed off contentedly to that sweet melody.

Researchers at Ohio State University College of Public Health and Temple University's Center for Obesity Research and Education have their own take on bedtime threats.

Their study, published in the “Journal of Pediatrics,” reveals that only 10 percent of preschoolers who go to bed before 8 p.m. become obese as teens, while 16 percent of those with bedtimes between 8 p.m. and 9 p.m., and 23 percent of those who hit the hay after 9 p.m. do!

According to the head researcher, epidemiologist Sarah Anderson, making sure your preschooler is in bed before 8 p.m. is something "families can do to lower their child's risk [of obesity], and it's also likely to have positive benefits on behavior and on social, emotional, and cognitive development."

The American Academy of Sleep Medicine says children ages 3 to 5 should sleep 10 to 13 hours in every 24-hour period (including naps).

We think you show love for your children by getting them to bed at the appropriate time. So we suggest Mom and Dad warm up their pipes around 7:30 and try singing "Golden Slumbers" (it has much sweeter lyrics): "Cares you know not, therefore sleep/While over you a watch I'll keep. Sleep, pretty darling, do not cry/And I will sing a lullaby."