Oh, sleep. Sweet, sweet sleep. It becomes quite a precious commodity for most new parents (though, there are apparently mythical, magical children who sleep through the night from day one), and remains an issue for many, even as their children grow. We know why we parents need sleep, but it’s important to understand why and how much babies and children need. And how to make sure they get it.

WHY?

According to Parents magazine, here are 7 reasons why your kids needs proper sleep:

1. Sleep promotes growth. “Growth hormone is primarily secreted during deep sleep,” says Judith Owens, M.D., director of sleep medicine at Children’s National Medical Center, in Washington, D.C. Mother Nature seems to have protected babies by making sure they spend about 50 percent of their time in this deep sleep, considered to be essential for adequate growth. Italian researchers, studying children with deficient levels of growth hormone, have found that they sleep less deeply than average children do.

2. Sleep helps the heart. Experts are learning more about how sleep protects kids from vascular damage due to circulating stress hormones and arterial wall — damaging cholesterol. “Children with sleep disorders have excessive brain arousal during sleep, which can trigger the fight-or-flight response hundreds of times each night,” says Jeffrey Durmer, M.D., Ph.D., a sleep specialist and researcher in Atlanta. “Their blood glucose and cortisol remain elevated at night. Both are linked to higher levels of diabetes, obesity, and even heart disease.”

3. Sleep affects weight. There’s increasing evidence that getting too little sleep causes kids to become overweight, starting in infancy. When we’ve eaten enough to be satisfied, our fat cells create the hormone leptin, which signals us to stop eating. Sleep deprivation may impact this hormone, so kids keep right on eating. “Over time, kids who don’t get enough sleep are more likely to be obese,” says Dorit Koren, M.D., a pediatric endocrinologist and sleep researcher at the University of Chicago. Worn-out kids also eat differently than those who are well rested. “Research has shown that children, like adults, crave higher-fat or higher-carb foods when they’re tired,” Dr. Koren says. “Tired children also tend to be more sedentary, so they burn fewer calories.”

4. Sleep helps beat germs. During sleep, children (and adults) also produce proteins known as cytokines, which the body relies on to fight infection, illness, and stress. (Besides battling illness, they also make us sleepy, which explains why having the flu or a cold feels so exhausting. It forces us to rest, which further aids the body’s ability to heal.) Too little sleep appears to impact the number of cytokines on hand. And it’s been found that adults who sleep fewer than seven hours per night are almost three times more likely to develop a cold when exposed to that virus than those who sleep eight or more hours. While there’s little data on young children, studies of teens have found that reported bouts of illness declined with longer nightly sleep.

5. Sleep reduces injury risk. Kids are clumsier and more impulsive when they don’t get enough sleep, setting them up for accidents. One study of Chinese children found those who were short sleepers (i.e., fewer than nine hours per night for school-age children) were far more likely to have injuries that demanded medical attention. And 91 percent of kids who had two or more injuries in a 12-month period got fewer than nine hours of sleep per night.

6. Sleep increases kids’ attention span. Children who consistently sleep fewer than ten hours a night before age 3 are three times more likely to have hyperactivity and impulsivity problems by age 6. “But the symptoms of sleep-deprivation and ADHD, including impulsivity and distractibility, mirror each other almost exactly,” explains Dr. Owens. In other words, tired kids can be impulsive and distracted even though they don’t have ADHD.

7. Sleep boosts learning. A baby may look peaceful when he’s sleeping, but his brain is busy all night long. Researchers at Columbia University Medical Center have shown that newborns actually learn in their sleep: Investigators played certain sounds for sleeping newborns, followed with a gentle puff of air on their eyelids. Within 20 minutes, the sleeping babies — who were between 1 and 2 days old — had already learned to anticipate the air puff by squinting. And as for that twitching all babies do as they snooze? It seems to be how their nervous system tests the connection between the brain and muscles. PS — Sleep aids learning in kids of all ages, and education experts are finding that naps have a particular magic.

HOW MUCH?

Now that we know why, how about how much? According to WebMD, this is how much sleep children need, by age:

• 1-4 Weeks Old: 15 – 16 hours per day
• 1-4 Months Old: 14 – 15 hours per day
• 4-12 Months Old: 14 – 15 hours per day
• 1-3 Years Old: 12 – 14 hours per day
• 3-6 Years Old: 10 – 12 hours per day
• 7-12 Years Old: 10 – 11 hours per day
• 12-18 Years Old: 8 – 9 hours per day

HOW?

We’ve got the why and how much, now how do we get them to sleep?! Parents magazine comes to the rescue again, with some suggestions:

• Encourage self-soothing. Try not to let your infant fall asleep while eating, and put her to bed when she’s still awake. By 3 months, you should slow your response time when she wakes up crying at night. By 6 months, when most babies typically sleep through the night, consider giving up the monitor if your room isn’t very far away. Or you can turn the volume down. You’ll be less tempted to rush to your fussing baby, and she’ll be more likely to drift back to sleep on her own.
• Create a solid routine. Children should have a consistent bedtime ritual by 3 months that lasts no more than 30 to 40 minutes, bath included, says Dr. Mindell. And for kids up to age 10, make sure bedtime is before 9 p.m. “Children who go to bed after 9 p.m. take longer to fall asleep, wake more often at night, and get less sleep overall,” she says. Dr. Durmer also suggests sticking with the usual bedtime sounds, like recorded ocean waves or a fan, and favorite sleep-time objects, such as a special blanket or pillow.
• Set the stage for sleep. Try to maintain the same temperature and level of light in your child’s room, even when on vacation, says Dr. Durmer. Shut off screens too, because research is mounting about the light generated by computers and tablets: Just two hours of screen time right before bed is enough to lower levels of melatonin — a chemical that occurs naturally at night and signals sleep to the body — by 22 percent. Ditch devices after dinner.
• Add another bedtime story. You already know reading to kids helps them learn, but hearing storybooks is a great way for kids to head off to dreamland. “Of all activities, reading printed books appears to be most relaxing,” says Michael Gradisar, a clinical psychologist at Flinders University, in Adelaide, Australia.
• Run a sleep audit. It makes sense to periodically measure your child’s sleep time, especially if you’re seeing trouble signs. (Alas, you’ll need to do it the old-fashioned way: Wearable trackers can make mistakes with anyone, but they’re especially inaccurate on kids, who move around more in all stages of sleep. A study found that one such device underestimated kids’ sleep by an average of 109 minutes.)