Sleep hygiene refers to the practices and habits people could use to sleep better. It includes routines such as regular bedtime, wake-up time, and avoiding coffee before bed. High-quality sleep allows your mind to rest, making you alert and refreshed in the morning. [1]

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The Science behind Sleep 

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Circadian Cycle

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Sleep is regulated by an internal "body clock" that works according to circadian rhythms. It is linked to adenosine levels - an organic substance our brain produces. As the day progresses and you become more tired, adenosine levels rise and regulate sleepiness. Then adenosine levels decrease during the night. 

Light is also influencing the circadian cycle. When the light disappears in the evening, it leads to the production of melatonin in your brain, making you tired and sleepy.

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Sleep stages 

Our sleep consists of 4 stages: 3 NREM (non-rapid eye movement) and 1 REM (rapid eye movement):

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Stage 1 NREM: the transition between wakefulness and sleep, which usually lasts for a few minutes and consists of light sleep. Your muscles relax, heart rate, breathing, and eye movements slow down. 

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Stage 2 NREM: the longest stage characterized by deeper sleep. Your heart rate and breathing will slow down more, and eye movements will cease. Your body temperature will also decrease. 

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Stage 3 NREM: plays an important role in making you feel refreshed and alert the next day. Heartbeat, and breathing, reach their lowest point. This stage will be longer at first and decrease in duration throughout the night.

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REM: first occurs about 90 minutes after you fall asleep. Your eyes will move back and forth quickly under your eyelids. Breathing rate, heart rate, and blood pressure will begin to increase. Typically, dreaming occurs during this stage, and your muscles become paralyzed to prevent you from acting out your dreams. It has also been linked to memory consolidation (the process of converting recently learned experiences into long-term memories). 

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These stages repeat in cycles (around 4-5 cycles per night), each lasting approximately 90-120 minutes. In total, adults should sleep about 7-9 hours in total. 

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Why Do We Need Sleep? 

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Adults need at least 7 hours of sleep to maintain the proper functioning of their body and mind. When you're asleep, your body replenishes and repairs itself, both mentally and physically. During sleep, new connections are made in your brain, a process called memory consolidation. Overall, your body needs this time to repair muscles, consolidate memories, release hormones that maintain growth and digestion, etc. 

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Sleep deprivation causes many different long-term effects in multiple systems of your body. It can lead to: 

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• Memory issues 
• Troubles thinking and concentrating
• Mood changes, irritability, and even anxiety or depression
• Accidents: Insufficient sleep can make you drowsy during the day, and sometimes you can even dose off for a few seconds; this is called "micro sleep". It is especially hazardous while driving or operating some heavy machinery since it can lead to life-threatening accidents. Furthermore, sleep deprivation leads to poor balance and coordination making you more prone to falls.
• Weakened immunity: You are more likely to get sick when exposed to germs.
• Diabetes: Insufficient sleep leads to decreased levels of insulin and insulin resistance. Insulin is a hormone that controls blood levels of glucose. When it's not working properly, you have a higher risk of developing diabetes mellitus.  
• Weight gain: Sleep affects the levels of two hormones that regulate our appetite. Leptin informs your brain when it's enough to eat, and ghrelin is an appetite stimulant. Lack of sleep leads to a reduction of leptin and an increase in ghrelin. 
• Risk of heart diseases: Insufficient sleep can lead to increased blood pressure, the release of proinflammatory molecules, and higher blood glucose levels. All these processes can contribute to the development of cardiovascular diseases. 
• Endocrine changes: In men, testosterone levels can drop, leading to a low sex drive. For its production, you need at least 3 hours of uninterrupted sleep. 

Waking up through the night can also affect the levels of growth hormones which help us build the muscles, repair cells and tissues, and promote growth. It is especially important in children. 

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13 Tips for Sleep Quality and Hygiene

1. Avoid daytime naps. If you need it, you can take a 15-30 min nap in the afternoon, but try to limit it. 
2. Regular physical activity can promote better sleep, but avoid being too active in the evening at least 3 hours before bedtime. 
3. Establish a routine before going to bed. Your relaxing bedtime routine can include, for example, a warm bath, soothing music, reading a book, etc. Once you repeat these activities every day for some time, it can signal your body that bedtime is coming and help you fall asleep easier. 
4. Follow a regular schedule. It is recommended to go to bed and wake up at the same time every day, even during the weekend. Frequent changes in the sleep schedule can confuse your biological clock. 
5. Separate your bedroom from other activities. You shouldn't eat, study, watch TV, or even read a book in your bed. It should just be associated with activities like sleep or sex. 
6. Remove electronic devices. Blue light suppresses melatonin production. It is recommended to stop using electronic devices at least 30 minutes before bedtime. 
7. Improve your environment. A comfortable bed, mattress, and pillows make it easier for you to fall asleep. Also, disturbing light, sounds, and high temperatures can disrupt sleep. You can use earplugs or listen to white noise to reduce unwanted sounds. The best temperature for sleep is estimated to be around 18 degrees celsius. Too high temperatures can make it harder for you to fall asleep and even lower the sleep quality. During the night, your core temperature drops, and you feel more comfortable in a colder setting. 
8. Avoid caffeine. It is a stimulant that makes falling asleep difficult. Caffeine effects typically wear off 6-8 hours after ingestion, so avoiding caffeine in the late afternoon is recommended. 
9. Avoid alcohol. It has some sedative effects that can make it easier for you to fall asleep but also disrupt sleep quality. You should avoid alcohol consumption at least 3 hours before sleep and limit your intake to 1 to 2 drinks per day.
10. Don't go to bed hungry or stuffed. Avoid large, heavy meals in the evening. Ideally, your dinner should be light and around 3 hours before sleep. 
11. Manage worries. Obsessive thoughts, anxiety, and ruminations make it challenging to relax and let your mind rest. 
12. If you can't fall asleep for longer than 15 minutes, get up and do something else, but don't use any electronic devices. For example, you can repeat your bedtime routine. 
13. If you followed all the steps, but it's still difficult for you to fall asleep, visit your doctor. Sleeping problems can be a sign of some other serious medical condition. [2]

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Sleep in Children 

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For good and efficient sleep in children, you can follow the same recommendations as in adults. However, there are some additional sleep strategies if you are having trouble getting your kid to sleep. [3]

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Experts recommend the following amount of sleep according to different age groups. 

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Newborns - 14–17 hours (includes naps)

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Infants - 12–15 hours (includes naps)

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Toddlers - 11–14 hours (includes naps)

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Preschool-aged children - 10–13 hours

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School-aged children - 9–11 hours

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Teens - 8–10 hours

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Tips for babies: Very young children don't have a circadian rhythm established yet, so they rarely sleep through the night without waking up. If they don't fall back asleep, try soothing them and talking to them without picking them up. If they keep crying, try feeding them or changing the diaper but do it only with a nightlight if possible. Babies don't have functioning thermoregulation developed yet, so they need a bit warmer conditions during the night, around 20-21 degrees celsius. They achieve temperature maturation by 11 weeks. Too warm temperatures during sleep can increase the risk of SIDS (sudden infant death syndrome).  

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Tips for toddlers: Young toddlers should have their sleep schedule supplemented by two naps during the day. They tend to stall and be stubborn before bedtime because they fear abandonment and missing out. Giving control over minor choices like pajamas or bedtime stories can distract them from these complaints. 

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Maintain a consistent schedule; although it might be tempting to let your kids sleep longer on the weekends, it can disrupt their biological clock. Also, try not to overschedule your kids with various activities, especially before night. If they are too tired, it can make them irritated and make it even more difficult for them to go to bed. 

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Sleep Disorders

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Some people suffer from sleep disorders that make it difficult for them to have sufficient good sleep. [4,5]

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Insomnia

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Insomnia is characterized by difficulty falling asleep, staying asleep, or waking up too early. It has a high prevalence among adults; around 10-15% of people worldwide have insomnia. Insomnia can be caused by stress, anxiety, and some mental and neurological disorders. However, most often, it's caused by inconsistent sleep schedules and poor sleep hygiene. 

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Obstructive Sleep Apnea (OSA)

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This disorder is characterized by the brief collapse of your airways during sleep, which causes pauses in breathing. These pauses can wake you up briefly, and you might not even remember these episodes. OSA leads to headaches and daytime fatigue and can cause serious cardiovascular diseases like coronary artery disease, heart attacks, heart failure, strokes, and abnormal heart rhythms (arrhythmias). 

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Circadian Rhythm Disorders 

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These usually occur due to an inconsistent sleep schedule. The most common types are the shift work disorder caused by night shifts and jet lag disorder. 

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Parasomnias

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Parasomnias are strange unusual behaviors during sleep. They include sleepwalking, sleep talking, teeth grinding, nightmares, night terrors, etc.

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