How many hours of sleep do you need, and how do you know you sleep enough?

How many hours of sleep do experts recommend?

The US National Sleep Foundation set out ranges by age. The American Academy of Sleep Medicine says, separately, that adults need at least 7 hours a night, regularly.

The range is a target, not a rule to the minute. Some people feel fine on 7 hours, others need 9. What matters most is that your hours are steady, night after night, not caught up at the weekend.

How do you know whether you sleep enough?

The clock on your bedside table tells only part of it. The next day tells the rest. You probably sleep too little if:

• you need an alarm and a few snoozes to get up;
• you sleep two hours longer at the weekend than during the week;
• you nod off quickly in front of the TV or on the train in the afternoon;
• you are irritable, forgetful or crave sweets;
• you need coffee to function after lunch.

The simplest test is a one-week journal. In the evening, note when you go to bed; in the morning, when you wake up and how you feel, from 1 to 5. After 7 days you see the link for yourself.

That is exactly what the daily journal in your free MentorSano account does: you log your sleep in a few seconds, and the platform shows how it changes from week to week, next to movement, meals and energy.

What happens when you sleep too little?

You feel one bad night the next day, and it passes. Short sleep for weeks and months matters more. The American Academy of Sleep Medicine links regularly sleeping under 7 hours with:

• weight gain and obesity;
• diabetes and high blood pressure;
• heart disease;
• lower mood and depression;
• weaker immunity, more mistakes and more accidents.

Poor sleep also spoils the next day's choices. When you are tired, you eat more, pick sweets more often and move less. That is the vicious circle: tired, more coffee and later in the day, worse sleep.

What helps you sleep better?

The UK's National Health Service (NHS) gives a few simple rules. Try them one at a time, one per week.

What you do	Why it helps
Go to bed and wake up at the same time, weekends too	Your body clock sets itself by regularity.
Last coffee before 2 pm	Caffeine stays in the body for many hours.
Screens away an hour before bed	Light and what you read keep you awake.
A dark, quiet and cool bedroom	The body falls asleep more easily as temperature drops.
Daylight in the morning, 10–15 minutes	It tells the body when it is day, and so when it is night.
Little alcohol, not late in the evening	It helps you fall asleep but spoils the second half of the night.
Movement during the day	Active people usually fall asleep more easily.

Does a sleep-tracking ring or watch help?

It can help you see the trend. Watches and rings estimate how long you sleep from movement and heart rate. They are fairly good at sleep duration and bedtime. They get sleep stages (deep, REM) wrong more often, so do not worry about one night with “little deep sleep”.

Use the numbers for trends over weeks, not for a single night. And put them next to how you feel: waking up rested matters more than a score.

What should you eat and drink in the evening to sleep better?

• Your last big meal 2–3 hours before bed. A heavy meal right before sleep can cause heartburn and restless sleep.
• No coffee, black or green tea or energy drinks in the afternoon. Caffeine is also in dark chocolate and some soft drinks.
• Little alcohol, and not late at night. It helps you fall asleep, but waking up in the second half of the night becomes more frequent.
• Fewer drinks in the last hour. That way you do not wake up to go to the bathroom.
• If you are hungry in the evening, a small snack helps more than going to bed hungry: a yoghurt, a banana, a few nuts.

Do afternoon naps help?

A short nap of 10–20 minutes in the early afternoon can restore energy without spoiling your night's sleep. Long naps or naps late in the day can make it harder to fall asleep at your usual time. If you need to sleep during the day every day, it is worth looking at how much and how well you sleep at night.