Sleep Better

Lesson 3: How much sleep you need

Goal: know the recommended amount for your age, find your own number, and wake up without cutting into your REM sleep.

The recommendations

These are the CDC’s figures, and they match the joint consensus of the American Academy of Sleep Medicine and the Sleep Research Society, whose experts reviewed the evidence and concluded that adults should regularly sleep 7 or more hours a night.

Note that this means hours asleep, not hours in bed. Most people need 7.5 to 8.5 hours in bed to get 7 to 8 hours of sleep.

Finding your own number

People genuinely differ. A simple way to find your need is to watch what happens on a holiday or a run of free days:

1. Go to bed when you feel sleepy, not by the clock.
2. Don’t set an alarm.
3. Ignore the first two or three days (you’ll be paying off debt and sleeping long).
4. Average the next week. That’s close to what your body actually wants.

This is a rough self-experiment, not a medical test, but it’s surprisingly useful.

If you regularly need well over 9 hours and still feel tired, mention it to your doctor; it can be a sign of a sleep disorder or another health issue.

Signs you’re not getting enough

• You need an alarm to wake up and hit snooze most days
• You fall asleep within a few minutes of lying down, every night (very fast sleep onset usually means high sleep debt, not a superpower)
• You nod off in meetings, on the couch in the evening, or as a passenger
• You sleep much longer on days off than on work days

Larks and owls

Your chronotype is your natural timing. Some people are naturally early (larks), some late (owls), most in between. Teenagers shift later, and most people drift earlier again as they age. You can nudge your timing with light (Lesson 4), but you can’t fully change it. Where you can, fit your schedule to your type.

Waking without an alarm

Because REM sleep is concentrated in the last part of the night (Lesson 2), an alarm that regularly cuts your sleep short takes a disproportionate share of your REM. If you have a pattern of long REM periods towards morning, which most people do, the alarm is cutting into exactly that.

The best fix isn’t to throw the alarm away; it’s to go to bed early enough that you wake naturally just before it. Then:

• Keep the alarm set as a safety net, but aim to beat it.
• If you’re always woken by it, move your bedtime 15 minutes earlier each week until you’re waking on your own.
• Keep your wake time fairly steady, even at weekends (within about an hour). A steady wake time is one of the strongest anchors for your body clock, and for anyone with insomnia it’s a core rule (Lesson 10).
• Whatever you do, don’t snooze. Snoozing gives you fragments of poor-quality sleep and more grogginess.

On days with no fixed start, skipping the alarm altogether is a good way to let your body finish its last cycle.

Exercise 3

Using the table, write down your target hours of sleep. Add 30 to 45 minutes for falling asleep and brief wakings, and count back from the time you need to be up. That’s your target bedtime. Is it earlier than your usual one?

Sources

• Centers for Disease Control and Prevention, About sleep
• Watson et al. (2015), Recommended amount of sleep for a healthy adult, AASM and SRS consensus statement
• Sleep Foundation, Stages of sleep
• Wittmann et al. (2006), Social jetlag: misalignment of biological and social time, Chronobiology International

This course is general information, not medical advice. If you have ongoing sleep problems, loud snoring with pauses or gasping, or sleepiness that affects driving or work, see your doctor. In Australia, if you are struggling or feel unsafe, call Lifeline on 13 11 14.