If you don’t get quality sleep, it can affect thinking, mood and long‑term health.

“Sleep is a pillar of health,” says Phyllis C. Zee, MD, PhD, a neurologist and chief of Sleep Medicine in the Department of Neurology at Northwestern Medicine. “It’s just as important as nutrition and exercise. It impacts everything.”

What Is Healthy Sleep?

Getting a good night’s sleep means waking up feeling refreshed enough to focus, move and enjoy daily activities. It’s not only about the hours of sleep you get — it’s also about your sleep patterns, such as how smoothly you fall asleep, how often you wake up throughout the night and how easily you return to sleep. Quality matters just as much as quantity.

For example, someone could reach the “right” amount of sleep, yet still feel tired if their night of sleep was broken up. Another person may wake briefly once or twice and still feel great if their overall sleep cycles were steady and restorative.

Most adults need seven to nine hours of sleep to feel rested. But sleep needs can differ due to:

• Your body’s circadian rhythm
• Genetics
• Daily activity level
• Recovery from short or disrupted sleep
• Certain medical conditions

Changing Sleep Needs

Sleep habits and timing can change for people who:

• Are pregnant
• Work overnight or have rotating shifts
• Take medications that affect alertness or sleep

These factors can make it harder to maintain a steady sleep routine, so paying attention to consistent sleep habits may help support better rest.

Signs You’re Getting Quality Sleep

These signs show you’re getting quality sleep:

• Falling asleep within 15 to 20 minutes of going to bed
• Returning to sleep without much effort when waking during the night
• Feeling alert for most of the day with steady mood and focus
• Little daytime dozing outside of planned naps
• Maintaining a regular sleep schedule — going to bed and waking up at the same time every day

Signs You’re Not Getting Quality Sleep

Common signs of poor sleep quality include:

• Trouble falling asleep or staying asleep
• Not feeling refreshed after what seems like enough hours of sleep
• Daytime sleepiness
• Low mood
• Problems focusing

The Role of Circadian Rhythm on Sleep

Your circadian rhythm is your 24-hour internal clock that regulates your sleep-wake cycle, hunger cues, hormone release and body temperature. Your brain houses your main internal clock, and your body has a network of clocks in each cell, working to control your circadian rhythm.

The circadian clock runs slightly differently for everyone. But delaying the sleep midpoint, which is the halfway point between falling asleep and waking, to 3 am or later, is linked to an increased risk of high blood pressure. Irregular sleep is also linked to an increased risk of Type 2 diabetes, even in people who sleep more than seven hours a night.

What influences circadian rhythm

Your body’s sleep time is determined by a variety of factors, including:

• More than 40% of your genes, which are regulated by your internal body clock
• Environmental cues, such as light exposure, physical activity and meal timing
• Bright light, which synchronizes your circadian rhythms and signals your brain to wake up  

Your chronotype: Are you an early bird or night owl?

There are two main sleep chronotypes:

• Early birds tend to go to sleep and wake earlier.
• Night owls tend to go to sleep and wake later.

Good sleep means aligning your internal clock with external factors. To sleep well, sleep at the right time of day for your internal and external clocks. A regular sleep rhythm is just as important as getting the recommended seven to nine hours of sleep.

How To Synchronize Your Sleep Schedule

Creating a routine that includes the following tips can help you set a steadier sleep schedule.

• Go to bed and wake up within the same one-hour window every day. (Don’t allow this window to vary by more than one hour.)
• Get as much daylight as possible in the morning. Light strongly influences the body’s natural sleep-wake cycle, tunes the circadian clock and can improve your mood. Bright light in the morning helps signal the body to be alert.
• Exercise at the same time each day and limit exercising late at night. Exercise can also help increase your ability to achieve deep rest.
• Carve out time during the day to relax, including naps. Your alertness will naturally drop midday.
• Allow two hours to prepare for sleep. Dim lights, limit screens and avoid eating large meals close to bedtime. Nighttime light, especially from smartphones, tablets and TVs, can make it more difficult to fall asleep and disrupt sleeping patterns.
• Keep your bedroom cool. Your body temperature naturally decreases during sleep.

How Much REM and Deep Sleep Do You Need?

Sleep moves through several stages each night, cycling between non-rapid eye movement (non‑REM) and rapid eye movement (REM) sleep about every 90 to 110 minutes. Adults typically spend about 20% to 25% of the night in REM sleep, the stage that helps support memory, learning and mood.

Deep sleep, sometimes called slow‑wave sleep, usually makes up 15% to 25% of the night and is the stage where the body focuses on physical recovery.

As people get older, deep sleep naturally decreases. While sleep trackers can show how much time you spend in each stage, how rested you feel in the morning matters far more than exact percentages.        

What Long‑Term Sleep Loss Can Do

More than 60% of adults in the United States get less than seven hours of sleep a night, which may increase the risk for several medical conditions.

Over time, sleep deprivation can raise the risk of:  

• Diabetes
• High blood pressure
• Heart disease
• Stroke
• Weight gain
• A weaker immune system
• Memory loss

When To Call Your Doctor

If you have persistent fatigue, it could be a sign of a sleep disorder like sleep apnea or chronic insomnia.

Signs to watch for include:

• Loud snoring
• Gasping or choking during sleep
• Repeated awakenings
• Insomnia
• Persistent daytime sleepiness that continues for weeks

If you’re noticing these symptoms for more than a few weeks, talk to your doctor about being evaluated for a sleep disorder. They may recommend keeping a sleep diary, trying home testing for certain sleep‑related breathing issues or completing a sleep study to better understand your sleeping patterns.

Treatment will depend on any underlying conditions but may include improving sleep habits, cognitive behavioral therapy for insomnia or other targeted therapies based on your results.