How much sleep do you really need?

On average, how many hours do you sleep per night? For most healthy adults, guidelines recommend at least seven hours of sleep.

But these are general recommendations, not strict rules. “Some people need less than seven hours, some need more,” says Eric Zhou of Harvard Medical School’s Division of Sleep Medicine.

Do you need more or less sleep?

We get it: You know people who swear they only need five hours of sleep per night, but feel groggy if they don’t get eight to nine hours of sleep. The main reason for individual differences is that we often look at sleep incorrectly.

“Instead of focusing exclusively on the number of hours we sleep per night, we should also consider our sleep quality,” says Zhou.

Sleep quality means how well you sleep at night. Did you sleep through the night? Or were there periods where you woke up? If so, did it take you a long time to fall asleep? How did you feel when you woke up?

“If you wake up refreshed and feel like you have enough energy for the day, I would worry less about the exact number of hours you sleep,” says Zhou.

How much sleep do you really need?

How does sleep quality affect your health?

Sleep quality is crucial to our overall health. Research has shown that people with poor sleep quality are at higher risk for diabetes, heart disease, stroke, and mental health issues like anxiety and depression.

And that’s not all. “Poor sleep can also increase daytime fatigue and make it harder to enjoy life,” says Zhou.

Still, it’s normal for people’s sleep patterns to change over time. “Many people won’t sleep exactly the same in their 50s and 60s as they did in their 20s,” says Zhou.

Many of these changes are age-related. For example, your circadian rhythm—which regulates many bodily functions, including our sleep-wake cycle—can naturally become disrupted over time. That means people spend less time in restorative deep sleep each night.

Production of the sleep hormone melatonin also gradually declines as we age. “Because of these changes, we may wake up earlier as we age than when we were younger, or wake up more frequently during the night,” Zhou says.

How can you track sleep quality?

How can you better understand the factors that likely contribute to your sleep quality? One way is to keep a sleep diary in which you track and record your sleep.

Each day, record what time you went to bed, how long it took you to fall asleep, whether you woke up during the night (and if so, how long you were awake), and when you woke up. Also record how you feel when you woke up and at the end of the day.

“Review the information after a week or two to see if you can identify any particular patterns that might be affecting your sleep quality, and then make adjustments,” Zhou says.

For example, if you have trouble falling asleep, go to bed half an hour later than usual but get up at the same time. “People with sleep problems often try to get more sleep by staying in bed longer, but this disrupts their sleep schedule and reduces their sleep quality,” says Zhou.

How much sleep do you really need?

Three key strategies to support your sleep quality

Other strategies that can help ensure good sleep quality include:

keeping a consistent wake time, especially on weekends

limiting daytime naps to 20 to 30 minutes and sleeping at least six hours before your desired bedtime

being physically active.

When it comes to sleep quality, consistency is key. “People with good sleep quality often have a predictable sleep window in which they sleep,” says Zhou. “Good sleepers are likely to sleep about the same number of hours and sleep through the night.”

The bottom line on restful sleep

It’s unrealistic to expect perfect sleep every night. “If you’re having trouble sleeping one or two nights a week, it may be related to the natural ups and downs of life,” says Zhou. “Perhaps you ate a big meal that day, drank too much alcohol while watching football, or had a stressful argument with someone. When you track sleep quality, you’re looking at your overall sleep health from week to week, not how you slept this Tuesday compared to last Tuesday.”

If you’re doing everything right for your sleep but still don’t feel rested when you wake up, talk to your doctor. This can help rule out a sleep disorder like sleep apnea or another health problem that can affect sleep, such as heartburn or high blood pressure. Other factors that can affect the quality of your sleep include taking multiple medications, depression, anxiety, loneliness, and environmental changes like temperature, noise, and light exposure.