Sleep stages


  1. Stages 1 and 2: Respiration and heart rate slows down, body temperature starts to drop, brainwave activity slows down.
  2. Stages 3 & 4: brain erupts with huge powerful brain waves. For reasons we don’t know, a ton of brain activity happens.
  3. Benefits of NREM:
    1. Helps strengthen and consolidation of the information you’ve been learning. Moves information from short term (fickle) memory to long term, so you’re far less likely to forget.
    2. In the deeper stages, your cardiovascular cycle slows down and your blood pressure drops. You switch to the quiescent mode (calm).
    3. Improves your immune system – restock the weaponry in your immune arsenal. It increases the amount, but also the sensitivity of our body to those immune things.


  1. Active state. Brainwave activity much faster and frenetic. Some regions are up to 30% more active relative to when awake – regions for emotions, memories, visual brain, motor activity, etc.
  2. Therapy at night – shows up in dream sleep. Soothing bond, takes the sharp edges off of those emotionally challenging events. Time during sleep, particularly during sleep, heals these wounds.
  3. Start integrating and associating information that we’ve learned. Seeks out and tests recent information and back catalog. Helps us be able to solve new problems.

How much sleep do we actually need?

  1. For the average adult, recommendation of 7-9 hours. But there’s a range of variability, some people may need closer to 9 hours.
    1. The number of people who can survive on <6 hours without showing impairment, rounded to a whole percentage, is 0%.
  2. What happens when we don’t get enough sleep? Daylight savings time –
    1. When we lose an hour of sleep in the spring, the next day there’s a 24% increase in the heart attack rate. When we gain an hour of sleep in the Fall, see a 21% reduction in heart attacks.
    2. See similar patterns for road accidents, suicide rates, harshness in federal judges sentencing.
    3. That’s how sensitive our bodies and minds are to sleep. Even if we don’t realize it.

Two factors for alertness and sleepiness

The two combined regulate alert/sleepiness:

  1. Sleep pressure (Adenosine): from the moment you wake up you start creating this Adenosine.
  2. Circadian Rhythm: controlled by the suprachiasmatic nucleus in the brain. It’s a rhythm as the name implies. Uses melatonin to communicate sleepiness.
    1. Daylight: signal to suprachiasmatic system to stop sending melatonin. As light intensity decreases (dusk) then suprachiasmatic system starts to sending melatonin.
      1. In modern offices, interior lighting may not be bright enough to register as daytime and reduce melatonin.
      2. At night at home, we use LED lights and have a lot of lights on that may stop or reduce melatonin production.

Melatonin misconceptions

  1. Melatonin doesn’t help improve the quality of the sleep for young adults. It does help with mid and late life. Be mindful about melatonin consumption. A study looking at 20+ brands saw a lot of variability in melatonin in the pills vs. what’s stated. In the US, melatonin is not regulated by FDA and some studies found 80% less to 480% higher.
  2. If taking melatonin, take between .5 – 3mg, above that the melatonin may be counterproductive, our brain may stop creating its own melatonin OR become less sensitive to it.

Social jet-lag 

Staying up later in the weekend and waking up even later. (e.g., waking up at 9-10am instead of 7am during the weekend). This makes it tough to sleep naturally at the right time on a Sunday night. A 2-3 hour lag in the weekend is torture to our sleep. Try to go to bed and wake up at the same time on weekdays and weekends.


Strongly genetic imprint, decides whether you’re a morning type or an evening type. We know of about 9 different genes that control how morning we are.

  1. Bear Chronotype should (source)
    • Drink alcohol between 5:30-7:30pm
    • Sleep between 11pm and 7am

Caffeine and good sleep

  1. Half life of caffeine is 5-6 hours. About 50% of caffeine is still circulating in your system 5-6 hours after drank. Quarter life of 10-12 hours! A cup of coffee from 2PM, a quarter of that coffee may still be there at midnight.
  2. Sleep quality disruption. Even if you can fall asleep, caffeine can reduce your deep sleep (stages 3-4 of the NREM) so you’re less refreshed.
  3. Body will vary in how quickly it metabolizes caffeine, so that changes things.
  4. Caffeine interacts with adenosine (sleep pressure chemical). Caffeine races to your brain and latches into the adenosine receptors, which blocks them. So it prevents the signal of adenosine to tell you that you’re sleeping.
    1. Your adenosine continues to build up regardless, so when the caffeine is metabolized then you’re hit with the huge wave of adenosine.
  5. Caffeine’s hidden places:
    1. Decaf coffee still has some caffeine (normally up to 5% of normal coffee, sometimes they’ve been found to have 20-30% of regular coffee).
    2. Energy drinks
    3. Some ice creams and dessert
    4. Dark chocolate can have as much caffeine as a cup of coffee


  1. Even one glass of alcohol in the evening has measurable changes in your sleep.
  2. Alcohol helps sedate you, but it doesn’t help you get into actual, restful sleep.
  3. Alcohol disrupts your sleep, which leads to sleep fragmentation and poor quality of sleep. Brief awakening so you don’t realize it.
  4. Alcohol can shift you into a more activated state in your nervous system, your fight or flight mechanism as you go to sleep. Also triggers stimulating neurochemicals which awakens you.
  5. Alcohol also disrupts your REM sleep. A study about learning tested the impact of a shot of vodka before bed:
    1. Relative to those that got natural sleep for a week, those with alcohol dosed with alcohol either on the first or 3rd night, they loss 30-50% of the information originally learned.
    2. After the first night of sleep your brain is not done with digesting that information.
  6. If you have weird dreams after alcohol, it’s because your brain tries to get more REM sleep when the alcohol has been digested, so closer to your wake up time.

Tips if you drink alcohol and caffeine

  1. Avoid caffeine in the afternoon (after noon or after 2pm at the latest). The dose and the timing matters. Only have a couple of cups of coffee in the morning only.
  2. If you get some drinks, maintain your regularity of sleep, even in the weekend. Regularity helps keep you in the standard cycle of sleep.

Last Updated on January 21, 2023 by Omar Eduardo