How much sleep do you need?

Politicians boast that they survive on three hours of sleep a night—but we need much more. It keeps us healthy and mentally sharp

Japanese prime minister Sanae Takaichi made the news recently when she announced she functions on just three hours’ sleep. She’s not the first world leader to need very little sleep: UK Prime Minister Margaret Thatcher slept for just four hours a night, while Winston Churchill managed on five.

And politicians are not the only ones. Around one in five of us get inadequate sleep because we suffer from insomnia, work night shifts or perhaps recently became a parent. Sleep apnea (inconsistent breathing) can also be a cause of insomnia, as can environmental factors and circadian-rhythm disorders such as jet lag.

But how much sleep do we really need, and what happens to us if we don’t get the recommended seven or eight hours every night? For one, our sleep needs are determined by our age: People over age 18 need seven to eight hours every night, but teenagers should be sleeping for up to 10 hours, and infants and toddlers up to age two should be sleeping as much as 16 hours every day.

And you can have too much of a good thing: sleeping nine or 10 hours a night as an adult isn’t good for us, either. Regularly oversleeping can cause chronic health problems and even shorten your life.

But don’t stress if you’re not even close to your optimum sleep needs. Our bodies can survive, and function healthily, on just four hours of sleep or less—and they can do it for two years or so.  But much beyond that, and we raise the risk of a host of chronic health problems, such as diabetes, obesity, dementia, heart disease and stroke. It can also affect us psychologically and it can lead to anxiety and depression.

So, we need our sleep—even if Sanae Takaichi thinks she doesn’t.

What sleep (or the lack of it) does to you

Optimum sleep: 7–8 hours

Essential “core” sleep: 6 hours

Daytime reactions affected: 5 hours

Hallucinations, neurotic thoughts: 3 hours or less

Psychological problems, such as cognitive decline and dementia: 5 hours or less*

Chronic health issues, such as heart disease and diabetes: 4 hours or less*

*If sleeplessness persists for two years or more

How much sleep you need

• Newborns (0–3 months): 14–17 hours per day
• Infants and toddlers (4 months–2 years): 11–16 hours per day, including naps
• Children (3–12 years): 9–13 hours per day
• Teens (13–17 years): 8–10 hours per night
• Adults (18–64 years): 7–9 hours per night
• Older adults (65+ years): 7–8 hours per night

Why sleep is good for you

• Strengthens memory and new information storage
• Aids glymphatic system function, which clears waste from the brain and reduces the risk of dementia
• Boosts brain cell function, including receptors for mood hormones such as dopamine and serotonin
• Improves cardiovascular health
• Supports mental health
• Strengthens immune system
• Enhances reproductive health

How to get a good night’s sleep

• Adopt good sleep hygiene techniques
• Maintain a routine—go to bed at a set time every night, even if you’re not sleeping
• Exercise during the day
• Meditate or read a calming book before you go to sleep
• Avoid caffeine, alcohol or heavy meals late in the day
• Reduce your light exposure in the evening
• Use blackout curtains in the bedroom
• Stop using electronic devices at least an hour before bed
• Don’t stress if you don’t fall asleep quickly

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