The Science of Sleep Hygiene

The Science of Sleep Hygiene

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Written by: Janine Cheng

Published on September 17, 2024

Sleep is not just a period of rest; it's a vital component of our overall health and well-being.

Yet many people struggle to get the quality and quantity of sleep their bodies need. Understanding the science behind sleep hygiene, including the role of cortisol levels, light exposure, and chemical releases during the sleep cycle, is crucial for optimizing our sleep habits and improving our health, both physical and mental.

Cortisol Levels and Sleep:

Cortisol, often referred to as the stress hormone, plays a significant role in regulating our sleep-wake cycle. Typically, cortisol secretion rises rapidly in the morning, helping us wake up feeling alert and energized. This is referred to as the cortisol awakening response (CAR). During the CAR period, cortisol levels increase by 38–75 %, peaking approximately 30–45 min post-awakening. As the day progresses, cortisol levels gradually decrease, reaching their lowest point in the evening, which prepares our bodies for sleep. However, disruptions to this natural rhythm, such as stress or irregular sleep patterns, can lead to imbalances in cortisol levels, making it harder to fall asleep or stay asleep throughout the night. To support healthy cortisol levels, it's essential to maintain a consistent sleep schedule and manage stress effectively through relaxation techniques like meditation or deep breathing exercises.

Light Exposure and Circadian Rhythm:

Light is one of the most influential external factors that regulate our circadian rhythm, the internal clock that controls our sleep-wake cycle. Exposure to natural light during the day helps synchronize our circadian rhythm, promoting wakefulness and alertness. Conversely, exposure to artificial light, particularly blue light emitted by electronic devices, in the evening can disrupt our natural sleep patterns by suppressing the production of melatonin, the hormone responsible for promoting sleep. To optimize sleep hygiene, aim for exposure to natural light during the day by spending time outdoors and limit exposure to artificial light, especially in the hours leading up to bedtime. It is recommended to aim for 5 to 10 minutes of sun exposure on sunny days and 15 to 20 minutes on cloudy days, within 30 to 60 minutes of waking. Consider using blue light filters on electronic devices or wearing blue light-blocking glasses to mitigate the effects of artificial light on sleep quality. 

Chemical Releases During Sleep:

During sleep, our bodies undergo a complex series of physiological processes that involve the release of various chemicals essential for rest and recovery. One of the key hormones released during sleep is growth hormone, which plays a crucial role in tissue repair, muscle growth, and overall physical recovery. Additionally, sleep is associated with the release of neurotransmitters like serotonin and dopamine, which regulate mood and emotional well-being. To optimize the release of these chemicals during sleep, prioritize good sleep hygiene practices such as creating a comfortable sleep environment, maintaining a consistent bedtime routine, and avoiding stimulants like caffeine and alcohol before bedtime. 

Tips for Optimizing Sleep Hygiene:

Establish a Consistent Sleep Schedule:

Go to bed and wake up at the same time every day, even on weekends, to regulate your body's internal clock. 

Create a Sleep-Friendly Environment:

Make your bedroom a comfortable and relaxing space by keeping it cool, dark, and quiet. Studies suggest that sleep is most efficient and restful when nighttime ambient temperature ranges between 68°F and 77 °F, with a 5-10 % drop in sleep efficiency when the temperature increases from 77 °F to 86 °F.

Limit Exposure to Screens Before Bed:

Avoid using electronic devices such as smartphones, tablets, and computers at least an hour before bedtime to minimize exposure to blue light. You may consider storing your phone out of reach and away from your bed to reduce the likelihood of screen use.

Practice Relaxation Techniques:

Incorporate relaxation techniques like meditation, deep breathing exercises, or gentle stretching into your bedtime routine to promote relaxation and reduce stress.

Limit Stimulants and Alcohol:

Avoid consuming caffeine and alcohol close to bedtime, as they can interfere with your ability to fall asleep and disrupt sleep quality.

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Citations: 

Szymusiak R. (2018). Body temperature and sleep. Handbook of Clinical Neurology.;156:341-351. doi: 10.1016/B978-0-444-63912-7.00020-5. PMID: 30454599.

Baniassadi A, Manor B, Yu W, Travison T, Lipsitz L. (2023). Nighttime ambient temperature and sleep in community-dwelling older adults. Sci Total Environ. PMID: 37474050; PMCID: PMC10529213.

Cho Y, Ryu SH, Lee BR, Kim KH, Lee E, Choi J. (2015). Effects of artificial light at night on human health: A literature review of observational and experimental studies applied to exposure assessment. Chronobiol Int. PMID: 26375320.

Elder GJ, Ellis JG, Barclay NL, Wetherell MA. (2016). Assessing the daily stability of the cortisol awakening response in a controlled environment. BMC Psychol. doi: 10.1186/s40359-016-0107-6. PMID: 26818772; PMCID: PMC4730747.

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