Is 9 Hours of Sleep Too Much?

Nine hours of sleep is usually not too much. It sits at the top of the 7 to 9 hours experts recommend for adults, and sleeping more than 9 hours is not necessarily harmful: it may even help young adults, people recovering from sleep loss and people who are sick ^[2]. Long sleep is worth a closer look when it is new, when it keeps creeping up, or when you still feel sleepy after it.

Why 9 hours can be perfectly normal

Sleep need is a range, not a single number. The joint statement from the American Academy of Sleep Medicine and the Sleep Research Society sets 7 hours as the floor for adults and says that sleeping more than 9 hours on a regular basis may be appropriate for young adults, people recovering from sleep debt and people with illnesses ^[1]. For everyone else, the experts said it was uncertain whether more than 9 hours carries any health risk ^[1].

So if you are 23, have been fighting a cold, or just finished a brutal month at work, a 9-hour night is your body doing its job. Eight hours, for the record, is squarely inside the normal adult range ^[2].

Who tends to need more

Young adults are the group experts name first: for them, more than 9 hours on a regular basis may be appropriate ^[1]. People catching up come next. After a run of short nights, sleep stretches out on its own and then shrinks back as the debt is repaid ^[4]. If you are ill or recovering, extra sleep may help ^[2], so a long night during a bout of flu is nothing to worry about.

Then there are natural long sleepers, who need 10 to 12 hours a night as adults. Their sleep is normal and good quality, just longer, and they feel alert and rested as long as they get it ^[5].

Long sleepers usually know who they are. The pattern starts in childhood and stays stable for life, rather than appearing suddenly ^[5]. If you have always been the one who needs a lie-in, that is very different from finding yourself needing 10 hours this year when you used to manage on 7.

What the "long sleep and mortality" studies really show

You may have seen headlines saying long sleepers die younger. They come from studies like a 2010 meta-analysis that pooled 16 studies with more than 1.3 million people. Both short and long sleepers had a higher risk of death than people who slept a medium amount, and for long sleep the risk was about 30% higher ^[3].

Before you set an alarm to cut your sleep, look at how these studies work. They ask people how long they sleep and then follow them for years. They cannot tell whether long sleep causes harm or is simply a sign of it. The authors themselves wrote that the link with long sleep may be explained by other illnesses and confounding factors, and that long sleep may be a marker of ill health ^[3]. Someone with undiagnosed heart disease, depression or a sleep disorder may sleep longer because they are unwell. The studies also defined "long" differently, from more than 8 hours to 12 or more ^[3].

The fair reading is that long sleep on its own has not been shown to cause harm, but a change toward much longer sleep is a reasonable prompt to check your health. The National Sleep Foundation's panel made a similar point: durations a little outside the recommended range can be fine, but habitually sleeping far outside it may signal a health problem ^[8].

Sleeping 10 hours and still tired

This is the combination to take seriously. If you regularly sleep long and still struggle to stay awake during the day, the problem is probably not how much you sleep but how well, or something going on elsewhere in your body.

A doctor will usually look at sleep quality first. Sleep apnea, for example, leaves people tired during the day and often comes with loud snoring and gasping or choking noises at night ^[7]. A rarer possibility is idiopathic hypersomnia, an uncommon disorder in which people are very sleepy despite 8 to 10 hours or more of sleep, take long naps that often don't refresh them and have great trouble waking up ^[6]. And the cause may lie outside sleep altogether: depression, iron deficiency anemia, diabetes and an overactive thyroid can all bring on ongoing tiredness ^[7].

Our guide to why you wake up tired goes through the everyday causes, like late caffeine and a warm bedroom, that are worth ruling out first.

How to tell whether you are repaying sleep debt

A long first night is often a clue that you have been running short. A study from Japan gave 15 healthy young men the chance to sleep up to 12 hours a night for nine nights. As far as they knew, they slept fine. On the first night they slept about 10.6 hours, more than 3 hours longer than usual at home. Their sleep then shortened over the following days and settled at an average of about 8.4 hours ^[4]. Even a shortfall of about an hour a night took about four days of extra sleep to clear ^[4].

You can run a rough version at home during a quiet week or holiday. Turn off the alarm, keep your usual bedtime and jot down each morning how many hours you got. If the first nights are long and then shrink, you were carrying debt, and the length you settle at is closer to your real need. Our sleep need calculator gives you a starting range, and the sleep debt calculator estimates how much you owe. If you are wondering about the opposite problem, see whether 6 hours of sleep is enough.

When to see a doctor

Long sleep on its own, with good energy in the day, rarely needs medical attention. Talk to a doctor if:

• you have felt tired for a few weeks and do not know why, or it is affecting your daily life ^[7]
• someone has noticed you gasp, snort or choke while asleep ^[7]
• you are very sleepy despite 8 to 10 hours or more of sleep, most days for more than three months ^[6]
• your tiredness comes with other changes, such as weight loss or low mood ^[7]
• you feel drowsy while driving or doing anything where falling asleep could be dangerous