# Sleep

## Who cares about sleep?

We spend close to 1/3 of our lives sleeping.

If someone isn’t getting enough sleep, improving sleep is *the* most dramatic lifestyle improvement.

Staying well-rested has many, many benefits:

- Physically [healthier](body-4_health.md)
- More [attractive](people-2_image.md)
- Better [memory](mind-memory.md)
- Generally [happier](happiness-1_why.md)
- More energy
- [Family and friends](people-4_friends.md) are happier because all the above makes you a generally better person to be around

Sleeping allows the body to heal and washes out waste from the brain.

- This means that sleep affects everything connected to thinking or the nervous system.
- Typically, if you can’t figure out your problem, you likely need more sleep.

Your mattress and pillow doesn’t have much effect on your sleep:

- Your mental state and surrounding environment determine more about your sleep than what you’re sleeping on.
- You can sleep fine as long as you’re on something relatively soft.
- A pillow will be more comfortable, but [*not* using a pillow can fix plenty of joint and back pain](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1119282/).

## Sleep has four stages

Stage 1:

- Slower brain waves and eyes start slowly rolling.
- Easy to wake someone in this stage.
- Muscles may jerk involuntarily.
- Transitioning in and out of this stage may feel like falling.

Stage 2:

- The first actual stage of "sleep".
- Specific brain wave spikes (sleep spindles) and structures (K complexes).
- Slower heart rate and lower body temperature.

Stage 3:

- The most restorative sleep cycle.
- Also known as "deep sleep".
- Waking someone from this stage is near-impossible.
- People usually don’t wake on their own from this stage.
- This stage is when most sleep disorders happen (e.g., night terrors, sleepwalking, sleep talking).

REM (rapid eye movement) sleep:

- The eyes move quickly back and forth.
- Typically, the stage where we experience [dreams](sleep-dreams.md).
- People waking during REM cycles will feel groggy and overly sleepy.

Good sleep persists through a general pattern:

1. Transition through Stages 1 and 2.
2. Move to REM after about 90 minutes.
3. Cycle back to Stage 3 after 10 minutes.
4. Shift back-and-forth between Stage 3 and REM, with longer REM cycles each time.
5. The sleep concludes with naturally waking up by phasing through Stages 2 and 1.

We can’t directly control sleep cycles, but we can typically alter them if we tell ourselves to wake up at a set time.

## Circadian rhythm

Each person has one of three natural patterns (chronotypes):

1. Morning people (early chronotype) - 10% of the population, where productivity peaks at 9 a.m.
2. Night owls (late chronotype) - 20% of the population, where productivity peaks at 9 p.m.
3. Mid-day (intermediate chronotype) - 70% of the population, with varying productivity across the day.

Learn how much sleep you require.

- Track when you naturally sleep with a sleep monitor app.
- Falling asleep within five minutes of lying down is a sign of sleep deprivation.

To completely reset your sleep cycle:

1. Stop eating for 12–16 hours.
2. Eat when you want to wake up.
3. Carry on through the day and fall asleep at your preferred time.

### Sleep schedules

You have [many sensible sleep cycles](sleep-cycles.md) to choose from.

- The body doesn’t need *hours* of sleep, just sleep *cycles*.
- Each sleep cycle without training lasts about 1.5–2 hours, and doesn’t need to be in order.
- Depending on your lifestyle, changing your cycles can enhance your [creativity](mind-creativity.md) or [productivity](success-4_routine.md).
- However, with any sleep cycle, there are still risks to [mental health](awareness.md) by staying up late.

If your sleep schedule gets disrupted, you may have to find a way to [resist insomnia](sleep-insomnia.md).