Sleep changes as you age. The amount of ZZZs your body needs, your ability to fall (and stay) asleep, your body’s response to lack of sleep . . . it’s a shifting landscape.

But healthy sleep is important at every age. Sleep benefits your physical and mental health.

“Your metabolism is at its most efficient when you’re well-rested,” says Dr. Bryan Hoff, Medical Director of the Sleep Center at Northfield Hospital and board-certified in sleep medicine. “Your brain works better too, which helps you think, learn and work at your best. That’s important at every age.”

Studies show that good sleep lowers risk for depression, cardiac distress, hypertension, swings in blood sugar and more. For kids, good sleep helps physical growth and cognitive development.

How can you tell if someone needs more sleep? There are different signs at every age.

Toddlers and children: Irritability, moodiness, poor emotional control. “Often, overtired kids can’t focus, and that lack of concentration is sometimes misdiagnosed as ADHD,” says Dr. Hoff. Talk to your pediatrician if you’re concerned.

Teens: Lack of concentration, poor impulse control and emotional control, riskier behavior. Chronically overtired teens have higher risks of depression and anxiety, especially after puberty. If you’re concerned about depression and sleep, contact your teen’s primary care provider.

Adults: Overeating, reliance on caffeine, lower productivity, coordination, concentration. Overtired adults feel run down: “They get tired of feeling tired,” Dr. Hoff says. If that’s you, consider a sleep study; you may have apnea, which can be treated.

Seniors: Daytime drowsiness, lower immunity, lack of concentration that can feel like memory loss . . . but isn’t. Body changes make it easier to wake up and harder to fall back asleep, so seniors often don’t get enough sleep at night. With lower sleep drive, you can sleep the edge off in a few hours, then wake up but aren’t fully rested. Chronic illness and some medications can affect sleep. “If you wake up feeling good but you’re tired 2 hours later, it may be your medication,” Dr. Hoff says. Talk to your primary care provider about the dose and timing of your medications; can you take it in the evening instead of morning?

So, what is “healthy” sleep? Check these five factors:

• Fall asleep within 30 minutes
• Sleep through the night (you might wake 1-4 times, but should fall back to sleep quickly)
• Wake up without an alarm
• Feel refreshed, without caffeine
• Stay awake most of the day

To find your own best sleep, try this simple test: Go to bed when you want, and wake up when you want. “You’ll learn your own best schedule and the number of hours of sleep that best suit you,” Dr. Hoff says. It may take 2-3 weeks to get your body functioning on the best sleep schedule for you.

Sweet dreams.