Why We Sleep: Unlocking the Power of Sleep and Dreams

by Matthew Walker

a living organism kept its own time, and was not, in fact, slave to the sun’s rhythmic commands.

when removed from the external influence of daylight, the internally generated “day” of each man was not exactly twenty-four hours, but a little more than that.

the average duration of a human adult’s endogenous circadian clock runs around twenty-four hours and fifteen minutes in length.

Melatonin simply provides the official instruction to commence the event of sleep, but does not participate in the sleep race itself.

For every day you are in a different time zone, your suprachiasmatic nucleus can only readjust by about one hour.

Caffeine has an average half-life of five to seven hours. Let’s say that you have a cup of coffee after your evening dinner, around 7:30 p.m. This means that by 1:30 a.m., 50 percent of that caffeine may still be active and circulating throughout your brain tissue. In other words, by 1:30 a.m., you’re only halfway to completing the job of cleansing your brain of the caffeine you drank after dinner.

Also be aware that de-caffeinated does not mean non-caffeinated. Depending on the decaffeination method and the bean that is used, one cup of decaf can have between 3 to as high as 10 percent of the dose of a regular cup of coffee.

First, after waking up in the morning, could you fall back asleep at ten or eleven a.m.? If the answer is “yes,” you are likely not getting sufficient sleep quantity and/or quality. Second, can you function optimally without caffeine before noon? If the answer is “no,” then you are most likely self-medicating your state of chronic sleep deprivation.

sleep helps to solidify new memories.

Practice does not make perfect. It is practice, followed by a night of sleep, that leads to perfection.

Depression is not, as you may think, just about the excess presence of negative feelings. Major depression has as much to do with absence of positive emotions, a feature described as anhedonia: the inability to gain pleasure from normally pleasurable experiences, such as food, socializing, or sex.

alcohol will often suppress REM sleep, especially during the first half or two-thirds of the night. When the body metabolizes alcohol it produces by-product chemicals called aldehydes and ketones. The aldehydes in particular will block the brain’s ability to generate REM sleep.

The obvious methods involve reducing caffeine and alcohol intake, removing screen technology from the bedroom, and having a cool bedroom. In addition, patients must (1) establish a regular bedtime and wake-up time, even on weekends, (2) go to bed only when sleepy and avoid sleeping on the couch early/mid-evenings, (3) never lie awake in bed for a significant time period; rather, get out of bed and do something quiet and relaxing until the urge to sleep returns, (4) avoid daytime napping if you are having difficulty sleeping at night, (5) reduce anxiety-provoking thoughts and worries by learning to mentally decelerate before bed, and (6) remove visible clockfaces from view in the bedroom, preventing clock-watching anxiety at night.