Humans spend roughly a third of their lives sleeping, and quality sleep is as essential to survival as food and water. Sleep allows your body and mind to recharge, and without sleep, the way nerve cells communicate with each other to perform necessary bodily functions – like breathing and keeping your heart beating – can be significantly disrupted.
How much sleep we get and how well we sleep will vary across phases of our lives, namely as we age. The hormonal changes that accompany aging can affect our sleep in a myriad of ways! Sleep is a complex process, and research is just beginning to understand its biological purpose.
The anatomy of sleep
Your body’s internal clock, also known as the circadian rhythm, controls when you feel tired and when you feel awake and alert. The circadian rhythm operates on a 24-hour cycle; after waking in the morning, the body tires progressively throughout the day, culminating in another night of sleep at the end of the day.
There are several factors that affect the circadian rhythm, including hormone fluctuation, travel to different time zones, shift work, sleep disorders, and stress. Natural light and artificial blue light also play a large role in regulating your circadian rhythm.
Hypothalamus – This peanut-sized structure found deep inside the brain contains groups of nerve cells that regulate our sleep and wake cycles. Within the hypothalamus are clusters of thousands of cells that receive information about light from the eyes and control your natural sleep and wake cycles.
Brain stem – At the base of your brain, the brain stem communicates with the hypothalamus to control the sleep and wake cycles. The brain stem sends signals to relax muscles in your body during sleep so your brain doesn’t cause you to act out your dreams.
Hypothalamus and cerebral cortex – These two parts of the brain interpret and process information from short-term to long-term memory and play important roles in dreaming and making sure our sleep is restful. Inside the hypothalamus, the pineal gland increases production of melatonin.
Stages of sleep
Sleep is divided into rapid eye movement (REM) and non-rapid eye movement (NREM) sleep. There are four stages of sleep you typically experience several times per night:
Stage 1 – NREM (N1) lasts around 1–5 minutes and is the dozing off stage of sleep. During this stage, your body hasn’t fully relaxed and may twitch. It’s very easy to be woken up during this stage.
Stage 2 – NREM (N2) lasts anywhere from 10 to 60 minutes. During this stage, your body falls further asleep. As your body relaxes, your internal temperature drops, your muscles relax, and your brain activity, heart rate, and breathing slow.
Stage 3 – NREM (N3) lasts around 20–40 minutes and is known as the deep sleep stage. Muscles, pulse, and breathing decrease further in this stage the more your body relaxes. You may become less responsive, and this is the stage where sleepwalking tends to occur.
Stage 4 – Rapid eye movement (REM) lasts anywhere from 10 to 60 minutes, typically occurring 90 minutes after you fall asleep. During REM sleep, brain activity increases, even nearing the level reached when awake. Your body experiences a temporary paralysis of muscles, except for muscles in the eyes and those that control breathing. REM sleep is essential to cognitive functions, like memory, learning, and creativity.
How much sleep do you need?
The amount of sleep you need changes as you age but also varies across different people in the same age group. Just like there’s no one way to diet, there’s no set number of hours of sleep that work for every person. The National Sleep Foundation provides recommendations for how much sleep any one person should get, based on age. Finding out how much sleep you need and focusing on what’s best for your own body (what IIN calls bio-individuality) is something you can experiment with until you find what works for you.
Newborns should and do spend anywhere from 14 to 17 hours asleep each day, though it may not feel like that to new parents. Babies don’t develop a circadian rhythm until they are several months old, causing their sleep patterns to be erratic at first. Infants and toddlers should have anywhere from 11 to 15 hours of sleep per day, and preschoolers should have approximately 10–13 hours.
School-age children, or those 6–13 years old, should sleep for 9–11 hours per day. Younger children typically need more sleep than those in middle school, and naps are still considered beneficial for children of these ages.
During puberty, teens may experience a shift in circadian rhythm, resulting in a drastic change in sleep and wake cycles. Teens’ melatonin levels may not rise to “tired” levels until much closer to 11pm or even later – but teens still need 8–10 hours of sleep each night. It’s estimated that as many as 69% of teenagers regularly don't receive enough sleep. Sleep deprivation can affect the development of a teen’s frontal lobe, which is critical to controlling impulsive behavior. Insufficient sleep at this critical stage of development can result in higher risk factors for diabetes, cardiovascular issues, mental health disorders, and high-risk behaviors.
Adults through middle age need at least eight hours of sleep per night. During this stage, they may go through significant hormonal changes, including both pregnancy and menopause. Adults are also much more likely to experience chronic or long-lasting sleep deprivation or insomnia due to shift work, caring for a child, and the general stress that comes with adulthood. Luckily, most people feel able to catch up on sleep on weekends or days off from work.
Adults 65 and older
Requiring slightly less sleep than younger adults, older adults need around seven hours of sleep per night. These periods of sleep are sometimes shorter, lighter, or interrupted by multiple nighttime awakenings. Physical health conditions that older people are more likely to experience, like heart diseases, diabetes, and arthritis, may also affect the quality and quantity of sleep.
The sleep-hormone connection
During sleep, several hormones are released into the bloodstream, all affecting your quality of sleep and ability to fall and stay asleep.
Known as the stress hormone, cortisol is a steroid made in the adrenal glands. It is mainly responsible for controlling blood sugar levels, regulating metabolism, and reducing inflammation. When cortisol levels get too high, blood pressure rises and sleep and wake cycles are disrupted.
Cortisol works in tandem with melatonin – as the day goes on, cortisol levels decrease, while melatonin levels increase, and vice versa. Chronic stress can throw off this balance and lead to bouts of insomnia or exhaustion.
Ghrelin, known as the hunger hormone, tells your brain when to eat. It slowly increases between meals and while we sleep. Ghrelin signals our bodies to wake up and seek out food. Studies have shown sleep deprivation can lead to increased appetite and, consequently, increased weight gain.
Working together with ghrelin, leptin, known as the satiety hormone, signals to the brain when you are full. Lack of sleep disrupts the release of leptin, impairing your body’s ability to manage hunger cues and blood sugar balance. This contributes to feelings of increased appetite when you don’t get enough sleep.
Melatonin is made in the brain’s pineal gland and is often referred to as the sleep hormone, with levels rising as daylight fades. Melatonin plays a very important part in regulating your circadian rhythm – levels are highest right after you wake and slowly decrease during the day. Melatonin is produced naturally in the body but is becoming increasingly popular to supplement as a natural sleep aid.
Insulin is the hormone responsible for shuttling sugar from the blood into cells, regulating blood sugar levels. Your blood sugar rises and falls during sleep, peaking between 4am and 8am for people with typical sleep and wake cycles. The surge of blood sugar prompts the body to release insulin to absorb glucose, keeping blood sugar balanced. But sleep deprivation can affect how insulin reacts in your body. Irregular sleep patterns have been shown to impact the production of insulin by making cells more resistant to it. This is called insulin resistance and can lead to many chronic health conditions.
Sleep and puberty
During puberty, bodies develop quickly and deal with a high influx of hormones, including sex hormones, like estrogen and testosterone. Along with these changes, teens experience a natural shift in circadian rhythms that don’t always match up with school times, and they are more likely to report being sleep deprived.
For people who experience menstruation, this extra influx of hormones can critically impact sleep. The increase in progesterone and estrogen during a woman’s cycle can result in premenstrual syndrome (PMS). A symptom of PMS is disrupted sleep. The pain associated with periods may also affect sleep. If period pain is affecting your sleep, talk with your medical provider.
Sleep and pregnancy
Progesterone and estrogen levels increase dramatically during pregnancy as the body prepares for birth. During the first trimester, progesterone levels increase to keep the uterine muscles relaxed and boost the body’s immune system in preparation for a baby. According to Yale Medicine, more estrogen is produced during one pregnancy than during the rest of someone’s life! Symptoms of pregnancy also affect sleep. Acid reflux, increased urination, and back pain all affect how well you sleep at night, and these symptoms are common, especially as pregnancy progresses.
Postpartum (the period after the baby is born) is a time when hormones fluctuate. After spending the previous 40 or so weeks creating life, the body changes jobs. Its estrogen levels drop to a point that affects sleep and can contribute to postpartum depression.
Sleep, menopause, and andropause
During menopause, low levels of estrogen can contribute to sleep disruption. This dip can set off hot flashes, uncomfortable periods of extreme heat that come on suddenly when no one else feels an increase in temperature. These hot flashes can bring you out of even the deepest REM sleep. People in the later years of life are also more likely to experience sleep apnea, a sleep disorder where breathing repeatedly stops and starts.
Andropause, sometimes referred to as male menopause or low T, is the natural decrease in testosterone levels as people age. These effects are very similar to what people going through menopause experience, including hot flashes, weight gain, low energy, and decreased sex drive.
Sleep health, optimized
While there is only so much we can do to regulate our own hormone production throughout our lives, we can try to balance hormone levels to limit impacts on our sleep health. Limiting blue light exposure late in the day, moving our bodies, and eating balanced, healthy meals are all ways to practice good sleep hygiene.
Health Coaches can support their clients in reaching life goals, including improved sleep health. Ready to learn how to help others improve their lives – not just with sleep but all aspects of health and wellness? Explore IIN’s Curriculum Guide to learn more about becoming a Health Coach.
IIN Content Writer
Katy holds a bachelor’s in English with a concentration in creative writing and advertising from Rider University. After jobs in the field of finance, she wanted to transition to an industry that focused on helping others be their best selves, and discovered IIN.
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