The science of sleep: How many hours do you need?

Conventional wisdom says eight hours is key when it comes to sleep.

But studies show eight might not be the magic number for everyone. So how do you know you're getting the sleep you need?

Many of us agree that we don't get enough of it. But that dragging, heavy-lidded feeling isn't the only bad result of sleep deprivation. Over time, poor sleep can lead to serious health risks. Short sleep duration is linked to obesity, type 2 diabetes, heart disease, depression and substance abuse. Lack of sleep also increases the risk of motor vehicle accidents. (Drivers, take note: The Centers for Disease Control and Prevention, or CDC, cites tiredness as a factor in up to 6,000 fatalities each year.)

Not only do healthy sleeping habits help lower the risk for sleep-related accidents and certain health conditions, but good sleep can also help you:

• Lower stress levels and improve mood
• Maintain a healthy weight
• Avoid getting sick
• Think more clearly and perform better on the job
• Make safe choices and reduce the chance of injuries

Sleep needs are individual and vary based on age. Adults generally find seven to nine hours per night adequate, while active, school-age children can require as many as 11 or 12 hours. The quality of sleep, or how well you sleep, also affects the quantity you need. People with frequently interrupted sleep, such as those with a sleep disorder like sleep apnea, won't feel as rested as people who sleep soundly through the night. Research has also linked sleeping too much to a higher risk of diabetes, heart disease, headaches, depression and fatigue. However, more research is needed to understand this possible association.

So the question is, how do you find the right number of hours of sleep per night for you?

It can take trial and error to find out how much sleep you need. Consider keeping a sleep log and noting your mood, energy level and health after different amounts of sleep. If you're feeling productive and happy on eight hours of sleep, you've likely found you're sweet spot. On the other hand, if you find it difficult to wake up or you rely on caffeine throughout the day to stay awake, there's a good chance you need more sleep.

Technology can also help you track your sleep patterns. For example, fitness devices can offer a peek into how much sleep you get each night.

The key to a good night's rest? Consistency—and a plan. Set a sleep and wake schedule and a regular bedtime routine, and stick to it, even on weekends. These healthy sleep tips can also help:

• Practice a bedtime ritual that's relaxing, such as reading a book
• Make sure your bedroom is at a comfortable temperature and minimize sounds and lights
• Exercise regularly, but avoid intense workouts within 90 minutes of bedtime, because it can make falling asleep more difficult
• Turn off all electronic devices at least a half hour before bed
• Invest in a comfortable pillow and mattress
• Avoid large meals, alcohol and caffeine in the hours before bedtime

Sometimes health problems can keep you from getting adequate sleep. See your healthcare provider if you have any of the following symptoms:

• Sleepiness during the day that makes it difficult to do everyday tasks
• Snoring
• Itchiness in your arms or legs or trouble moving your arms or legs when you wake up
• Trouble breathing or gasping during sleep
• Insomnia (trouble falling or staying asleep) or another issue that keeps you from sleeping well
• Tiredness after a good night's sleep

Your healthcare provider can help figure out the cause of your sleep troubles and get you on your way to a better night's sleep.

Clinically reviewed and updated May 2021.