Toddlers need a lot of sleep, kids a little less, and teenagers at certain phases need more than kids, up to 10 or 11 hours per night. It seems that teenagers especially benefit from sleeping in, perhaps because growth hormone is released in the early morning. They naturally stay up late, even in traditional cultures without artificial lights. Young adults are still finishing growth, such as bone formation, through college and beyond.
Adults tend to fall into a preferred pattern of early or later waking. There are early birds, night owls, and the majority in between, with 5-10 hours of sleep depending on life circumstances. Pregnant and nursing women generally need extra sleep, while some rare people do well with just 5-6 hours per night.
Whatever your preferred sleep window and length, it’s important to respect your body and carve out the time necessary to sleep. While the human body can function on short sleep if necessary, unless you’re living through a war or family crisis, you can probably make time for rest. Being under slept makes learning harder, and compromises the fancier functions of your brain, like remembering new vocabulary words, noticing the emotions of people around you, and imagining new solutions to challenging problems. Being chronically under slept also impairs the more basic bodily functions like digestion and repair.
One surprising effect of poor sleep is increased hunger, cravings for fat and sugar, and an impaired sense of fullness. This is because of the hormones leptin and ghrelin, among others. Leptin is a hormone made by fat cells which decreases your appetite. Because if you have enough body fat, you don’t need to eat, right? Ghrelin is a hormone that makes you hungry, and it typically stays down for a bit after you eat. In cases of sleep loss, though, these don’t send their messages clearly from the brain to the receptors around your body.
Sleep is also a time of brain cleaning and metabolic reset. It’s thought that poor sleep is a contributing factor to Alzheimers’, because the brain is supposed to be cleaned every night, and if the cleaning time is reduced, waste products build up over time and then lead to the death of brain cells, and thus, memories. Also, since poor sleep tends to damage our appetite control and induce cravings for less nutritious food, poor sleepers often end up overweight and develop insulin resistance, which leads to higher level of sugar circulating in the blood. The brain uses a lot of energy, but the amount of sugar has to be modulated carefully, so the body seems to prioritize sugar management in the brain over cleaning, which again contributes to the build up of plaques in the brain as debris is not cleaned, and then cells die.
While it’s not yet common to look for Alzheimers in middle-aged people, many researchers think that the patterns and changes of Alzherimers are evident 20 to 30 years before symptoms emerge. For young people, it makes sense to start considering how they can treat their bodies and brains well, and develop good habits that can see them through middle age and give them the best odds of having a good brain into older age.
Teens and adults often stay up late to get time alone or more time with friends. In our Health Classes, I encourage teens to remove their electronics and set their rooms up for good quality sleep over enough hours, and to sleep in or nap when possible, if naps don't disrupt their sleep at night.
There are many chemicals which relate to sleep. Three of the major ones are Adenosine, Cortisol, and Melatonin. Adenosine is the “sleepiness chemical” that builds up over the course of the day. When we drink caffeine, it temporarily blocks adenosine, so we feel less tired.
Cortisol, the “awake and alert” chemical, starts out high in the morning and then gradually goes down over the course of the day. Under times of stress, the body may get the message to keep producing cortisol, and sometimes a pattern develops of low morning cortisol and high afternoon or evening cortisol. This can cause a slow start in the morning, and make it harder to fall asleep at night.
Melatonin, the chemical made at night to promote sleep, goes up when cortisol goes down. If cortisol is high, it’s hard for melatonin to rise, which is why it can be hard to fall asleep when we have a lot on our mind keeping us “awake and alert”. Melatonin is sometimes taken as a supplement to help fall asleep. Supplemental melatonin releases quickly, while natural melatonin releases slowly and peaks later in the night.
Humans don’t naturally have a consistent 16 hours awake and 8 hours asleep; we rely on cues from the environment to tell us when to wake up and fall asleep. Circadian rhythm is the term used for the pattern of waking and sleeping, that is largely determined by sunlight. Sunlight and fluorescent lights contain more cool “blue light”, while a campfire or certain light bulbs contain warm “red light”.
Exposure to blue light at night can send confusing messages to the brain, so it’s recommended to limit lights and screens after dark if you need help sleeping. Vitamin A may also help the eyes to be more sensitive to sunlight, and thus better able to set your circadian rhythm.
We’ve all seen the toddler melt down in the store after missing a nap, and we take it as a given that a small person can’t hold it together without enough sleep. Really, everyone’s brain benefits from good sleep, particularly through the Prefrontal Cortex.
The Prefrontal Cortex is the part of the brain responsible for “executive functions”. It’s the boss who manages impulses and decides what’s best to notice and do. The Prefrontal Cortex relates to working memory (how many things you can remember at once), impulse control, planning and executing complex behavior. It also helps when considering and prioritizing competing and simultaneous information, ignoring external distractions, focusing attention, and the development of personality.
The association between depression, anxiety, and sleep disturbance has been noted for many years. It was always assumed that the anxiety caused the sleep disturbance, but recent studies point out that it work the other way as well, with sleep disturbances quickly producing depression (10 times more likely) and anxiety (17 times more likely).
I’ve always figured I could be a nice person with sleep debt it I were a saint... but since I’m not, I should just try to get enough sleep, so I won’t traumatize my family, or continually be losing things. Your automatic reactions might be kind and loving, even with sleep deprivation, but most of us were raised by imperfect humans who modeled imperfect responses that we would like to improve upon. Doing better than automatic takes grace and a functioning Prefrontal Cortex. In order to plan and respond rather than simply react, our best thinking parts should be fully online.