Adequate sleep increases your motivation for exercise, your peak muscle strength, your ability to respire and expel carbon dioxide, and your ability to sweat. It also reduces injury risk.

Human beings seem to be the only species that will deliberately deprive themselves of sleep for no apparent reason

A cup of coffee in the evening can decrease the amount of that deep non-rapid eye movement sleep by somewhere between 20-40% at night. And for a spot of context, I'd have to age a healthy adult by probably about 10-15 years to produce that kind of a reduction in deep sleep.

More recently, we've discovered that REM sleep is significantly associated with your longevity, and the less REM sleep that you have predicts a shorter lifespan.

Avoid eating simple carbs too close to bedtime as they tend to raise your core body temperature (in order to fall asleep, you need to drop your core body temperature by 2 to 3 degrees Fahrenheit)

Sleep deprivation simulates conditions of starvation - the hunger hormone (ghrelin) is increased and the satiety hormone (leptin) is suppressed

If you have a cup of coffee at 2 PM, it would be the equivalent of getting into bed at midnight, and just before you turn the lights out, you swig a quarter of a cup of coffee and you hope for a good night of sleep. And it tends not to happen.

Relative to their morning type counterparts, evening types are 2-3x more likely to be diagnosed with depression, 2-3x more likely to experience feelings of being depressed for weeks in a row, and also 2-3x more likely to have lost interest in most things that feel good in life. Unsurprisingly, and as a result, evening types are twice as likely to be using antidepressants relative to morning types.

If you limit people to just 6 hours of sleep a night or 5 hours of sleep or even 4 hours of sleep a night for several days or even several weeks, there is a common outcome: They will consistently eat more food relative to those same individuals when they're getting a full night of sleep.

If you are struggling with sleep at night, do not nap during the day. Instead, stay awake across the day and build up as much of that healthy sleep pressure as possible to set yourself up for the best chance of both falling asleep and staying asleep.

And indeed, if I were to place electrodes on your head, I could show you this reliable drop in your brain's physiological alertness that happens each and every afternoon. And what this means is that us humans may not have been designed to sleep in a single bout at night, which is what we call monophasic sleep. Rather, we may have been designed to sleep in two bouts. In other words, one longer bout at night and then a siesta-like nap in the afternoon.

All stages of sleep are critical. Different types of sleep perform different functions for the brain and the body at different times of night. But we need all of those stages of sleep—there is no one stage of sleep that's more important.

Aim to stop eating 3 hours before bed

If you look at the contribution of different sleep stages to your lifespan, REM sleep was the strongest predictor of your longevity. And it was a linear relationship ... The less and less REM sleep that you were getting, the higher and higher your probability of death.

There were three really good randomized placebo crossover trials with tart cherries. And what they found was that in one study, it reduced the amount of time that you spent awake at night by over an hour. And in the other two studies, one of them found that it increased the amount of sleep that you got by 34 minutes; the other it increased the amount of sleep that you got by 84 minutes.

Levels of the hunger hormone, which is ghrelin, will rocket up when you're not getting sufficient sleep; they will increase by up to 28%.

Some people will tell me, 'Look, I am one of those individuals, and I can have an espresso with dinner, and I fall asleep, and I stay asleep. So, no harm, no foul.' Well, yes, and no. Even if you fall asleep easily and then you stay asleep across the night, caffeine will still decrease the amount of deep sleep that your brain can generate.

In the first half of the night, the majority of your 90-minute sleep cycles [are] going to be comprised of lots of deep non-REM sleep and very little REM sleep. But as you push through to the second half of the night, now that seesaw balance will actually change, and instead, the majority of those 90-minute cycles are going to be comprised of much more rapid eye movement sleep, or dream sleep.

Don't go to bed to full and don't go to bed too hungry

Caffeine has, what we call, a half-life of about 5-6 hours in the average adult. In other words, after 5-6 hours, 50% of that caffeine is still going to be in your system. And what that means is that caffeine will then have a quarter-life of about 10-12 hours.

If you're not getting sufficient sleep in the week before you get your flu shot, you end up producing less than 50% of the normal antibody response, therefore rendering that flu vaccination significantly less effective.

On average, men are more evening types than women with men wishing to go to bed around 30 minutes later in the evening and wake up 30 minutes later.

And without that dream sleep, we know that we can suffer impairments in our cognitive brain function as well as our emotional stability. And we can also experience a heightened amount of negative moods, including things such as anxiety.

Coffee ends up being the single biggest source of antioxidants for many people in developed nations—and not by a small margin either.

When we use these devices, the reason that they're so disruptive to our sleep is less about their blue light; it's more the fact that we are masking sleepiness with this overriding artificial activation from the devices.

It's best to aim for a nap of usually less than 20 minutes. And the reason I say that is, otherwise, you can start to plunge deeper into your sleep cycle ... And when you awake, if you sleep longer, you can have what we call a 'sleep inertia'—it's almost like a little short sleep hangover where you feel worse rather than better...

Even if you can have a cup of coffee, or several, with dinner and you can fall asleep and stay asleep, you can still suffer impairments in both the quantity as well as the electrical quality of your deep non-rapid eye movement sleep.

The second issue with alcohol is that it fragments your sleep. In other words, alcohol will litter your sleep with many more awakenings throughout the night.

Alcohol is one of the most potent suppressors of REM sleep, and that's perhaps concerning, considering that REM sleep is associated with a constellation of different benefits, both for your brain and also for your body.

It's these antioxidants that we believe are the principal explanation for why coffee is associated with so many health benefits. It's not the caffeine itself; it's the antioxidants associated with the coffee bean.

Your sensitivity to caffeine is due, in part, to your genetics, and different people will have a more or less efficient version of an enzyme that breaks down caffeine.

It's not just that exercise helps sleep, sleep profoundly helps exercise

I think evening types should be allowed to sleep when they are biologically designed to sleep and wake up. But I'm also a realist, and I understand why trying to change night owls into morning larks may be seen as helpful.

Now, if you were to give your circadian rhythm a personality trait, it would be labeled as a creature of habit. It never stops ticking out its rising and falling rhythm—day after day, night after night.

Sleep deprivation causes a change in your appetite profile - you want to eat more and you're less satisfied with your food

Blue light exposure at night prevents the pineal gland from releasing adequate levels of melatonin

Adenosine build-up drives the need for deep sleep.