Just like food and water, sleep is an indispensable part of our daily needs. While we may think sleep merely rests our weary bodies, our brains remain active throughout the night, playing a critical role in both brain and physical functioning.
What Happens During Sleep?
Our internal body clock, known as the circadian clock, dictates when we’re ready to sleep. Several circadian clocks exist in the body, located in the brain and other organs. They’re triggered by cues like daylight (making us feel alert) and darkness (inducing drowsiness). Artificial bright light, caffeine, and alcohol can also trick these clocks into making us feel awake, even at night.
Our bodies cycle through different sleep phases, classified as REM (rapid eye movement) and non-REM sleep, approximately 4-6 times per night. Briefly waking up between cycles is not uncommon.
Hormones Regulating Sleep Cycles
Various neurotransmitters and hormones released by the brain send signals to promote sleep or wakefulness, often stimulated by light or darkness.
- GABA decreases nerve cell activity, playing a major role in allowing the body to sleep.
- Adenosine gradually accumulates in the brain during the day, making us sleepy at night. Caffeine blocks adenosine receptors, keeping us awake.
- Melatonin is released by the brain in darkness, signaling the body to sleep. Sunlight inhibits melatonin production and increases cortisol release, waking us up. Excessive artificial light at night can disrupt melatonin release, making it harder to fall asleep.
- Serotonin, the “feel-good” chemical, is associated with both sleep and wakefulness. The brain releases it during the day and uses it to form melatonin at night.
- Hormones like norepinephrine, adrenaline, histamine, and cortisol counteract sleep, causing alertness and wakefulness, especially in response to stress.
Immediate Effects of Sleep Deprivation
About one-third of American adults don’t get enough sleep each night, according to the Centers for Disease Control and Prevention (CDC). Short sleep duration in adults is defined as less than 7 hours in 24 hours. Up to 70 million Americans have chronic sleep problems, leading to poor sleep health being a Healthy People 2020 goal.
Sleep helps process thoughts and store memories, so a lack of quality sleep can lead to difficulty focusing, thinking clearly, feeling tired, irritable, or anxious during the day. Work or school performance may suffer, reaction time may slow (increasing accident risk), and children may experience attention, behavior, or hyperactivity issues. In the elderly, lack of sleep may decrease focus and attention, raising the risk of falls, fractures, and car accidents.
Reasons for insufficient sleep include poor sleep habits, unsuitable sleep environments, working against the body’s circadian clock, sleep disorders, or medical conditions.
How Much Sleep Do We Need?
Sleep needs change with age, generally requiring less sleep as we get older, but individual differences exist. The National Sleep Foundation and American Academy of Sleep Medicine (AASM) recommend:
- Newborns: 14-17 hours/day
- Infants: 12-16 hours/day, including naps
- Toddlers: 10-14 hours/day
- Preteens and teenagers: 8-12 hours/night
- Adults: 7-8 hours/day
The AASM and Sleep Research Society recommend adults sleep 7+ hours/night for optimal health. However, individual requirements vary, and factors like sleep quality are important. Sleeping less than 5 hours or more than 9 hours per day is associated with increased health risks like obesity, diabetes, and cardiovascular disease for most healthy adults.
While “catching up” on sleep by sleeping in or napping may seem tempting, it disrupts the body’s circadian rhythms and may deprive it of deeper sleep stages. Increased variability in nightly sleep duration is also linked to higher metabolic and heart disease risk. It’s best to respond to the body’s natural sleep signals whenever possible.
Sleep Hygiene Tips
- Set a consistent sleep schedule, even on weekends, to regulate your body’s sleep cycles and circadian rhythms.
- Exercise during the day, but avoid vigorous activity one hour before bedtime.
- Avoid large meals, heavy snacking, or alcohol 2-3 hours before bed.
- If you’re caffeine-sensitive, avoid caffeinated beverages 4-6 hours before bedtime.
- Stop using electronic devices an hour before bed, especially those emitting blue light.
- Schedule before-bed activities to signal winding down, like changing into pajamas and brushing teeth.
- Create a quiet, dark, relaxing bedroom environment with a comfortable temperature.
- Practice calming bedtime rituals like deep breathing exercises, light yoga stretches, or soothing relaxing music.
- If you can’t return to sleep after waking up, get up and do quiet, relaxing activities until you feel tired again.
By understanding the intricacies of sleep and implementing healthy sleep habits, we can unlock the door to optimal well-being and vitality.
